TREE-RING DATING OF OAK PANELS FROM THE PAINTING
“GRAY-BEARDED MAN HOLDING SHELL”
Henri D. Grissino-Mayer
Laboratory of Tree-Ring Science
Department of Geography
University of Tennessee
Knoxville, Tennessee 37996
Henri D. Grissino-Mayer, Principal Investigator
Final Report
Submitted 7 July 2006
Tree-Ring Dating of Oak Panels from the Painting
“Gray-Bearded Man Holding Shell”
Table of Contents
Executive Summary .................................................................................................................. 1
How Tree-Ring Dating Works ................................................................................................ 2
Assigning Calendar Years to Tree Rings by Crossdating...................................................... 3
Tree-Ring Dating of Panel Paintings: A Short History.......................................................... 4
Background to this Research Project....................................................................................... 9
Methods ...................................................................................................................................... 9
Surface Preparation .............................................................................................................. 9
Obtaining Tree-Ring Measurements...................................................................................... 10
The Baltic 1 Reference Chronology....................................................................................... 11
Graphical Crossdating .......................................................................................................... 12
Statistical Crossdating .......................................................................................................... 15
Results ........................................................................................................................................ 16
Original Position of the Panels.............................................................................................. 16
Graphical Crossdating .......................................................................................................... 17
Statistical Crossdating ........................................................................................................... 20
Conclusions ................................................................................................................................ 23
References Cited in this Study ................................................................................................. 25
List of Figures
Figure 1. Sequence of tree rings from a red oak .................................................................. 30
Figure 2A. Crossdating a sequence of undated tree rings .................................................... 31
Figure 2B. The undated tree rings now dated ...................................................................... 31
Figure 3. A triptych by Rogier van der Weyden................................................................... 32
Figure 4. The painting that was analyzed ............................................................................ 33
Figure 5. Polishing the panel surfaces .................................................................................. 34
Figure 6. Securing the painting in a custom-designed brace ................................................ 35
Figure 7. Ensuring the vertical alignment of the painting..................................................... 36
Figure 8. Example of a 2 X 2 contingency table used in chi-square analysis ....................... 37
Figure 9-1. The tree rings seen on Panel 1............................................................................ 38
Figure 9-2. The tree rings seen on Panel 2............................................................................ 38
Figure 9-3. The tree rings seen on Panel 3............................................................................ 38
Figure 10. Locations in a log from where panels can be cut ............................................... 39
Figure 11. Skeleton plot comparing Panel 2 against the Baltic 1 chronology ...................... 40
Figure 12A. Line graph comparing Panel 2 against the Baltic 1 chronology....................... 41
Figure 12B. Line graph comparing Panel 2 against the Netherlands Baltic chronology ..... 41
Figure 13. Final dated positions for the three panels ............................................................ 42
List of Appendices
Appendix 1: Complete listing of published articles that used
tree-ring dating on panel paintings .................................................................................. 43
Appendix 2A: The “Baltic 1” reference tree-ring chronology
supplied by the University of Sheffield .......................................................................... 50
Appendix 2B: The “Baltic 2” reference tree-ring chronology
supplied by the University of Sheffield .......................................................................... 51
Appendix 3A: Original measurements for Panel 2 .............................................................. 52
Appendix 3B: Original measurements for Panel 1 .............................................................. 53
Appendix 3C: Original measurements for Panel 3 .............................................................. 54
Appendix 4A: COFECHA output that compares the tree rings
from Panel 2 with the Baltic 1 reference chronology ..................................................... 55
Appendix 4B: COFECHA output that compares the tree rings
from Panel 2 with the Baltic 1 reference chronology (25-year lag) ............................... 56
Appendix 5A: COFECHA output that compares the tree rings
from Panel 1 with the Baltic 1 reference chronology ..................................................... 57
Appendix 5B: COFECHA output that compares the tree rings
from Panel 1 with the Baltic 1 reference chronology (25-year lag) .............................. 58
Appendix 6A: COFECHA output that compares the tree rings
from Panel 3 with the Baltic 1 reference chronology ..................................................... 59
Appendix 6B: COFECHA output that compares the tree rings
from Panel 3 with Panel 1 ............................................................................................... 60
Tree-Ring Dating of a Panel Painting
Page 1
EXECUTIVE SUMMARY
In 2004, the Laboratory of Tree-Ring Science at the University of Tennessee was
presented a panel painting which the owner attributed to the Dutch master Rembrandt van Rijn.
Our goal was to use dendrochronological techniques to assign calendar dates to the tree rings on
the three panels that make up the painting in an attempt to help experts assign a painter to this
remarkable work of art. After polishing the panel surfaces, we measured the widths of all tree
rings in the nearest 0.01 mm using a Velmex moving stage micrometer on which was mounted a
specially-designed brace system for securing the painting. We used both graphical and statistical
techniques to assign absolute calendar years to the tree rings (“crossdating”) on the three panels.
We used primarily the “Baltic 1” reference tree-ring chronology developed at the University of
Sheffield, but also found very convincing agreement with tree rings from the Netherlands Baltic
reference chronology. Panel 2 had tree-ring patterns that were by far the most convincing both
graphically and statistically. Tree rings on Panel 2 date from A.D. 1369 to 1585. The tree rings
from Panel 1 crossdated from A.D. 1338 to 1543. Panel 3 crossdated convincingly with tree rings
from Panel 1 and date from A.D. 1393 to 1589. Curiously, the tree rings from Panel 2 dated more
strongly against the Netherlands Baltic reference chronology, suggesting the tree rings from this
painting have more in common with works of art housed specifically in museums in the
Netherlands. Using published estimates for sapwood rings and allowing for seasoning time, the
year in which the tree(s) was harvested to make these panels could range between A.D. 1601 to
1613, but the actual harvest year could be much later. We can safely conclude that whoever
painted this masterpiece must have lived and painted in the early to mid-1600s. The
analyses performed in our laboratory support its possible attribution to Rembrandt van
Rijn.
Tree-Ring Dating of a Panel Painting
Page 2
HOW TREE-RING DATING WORKS
Trees are intimately bound to the environment, making them one of the most consistent
and dependable recorders of processes and events that occur in nature. Trees are sensitive to both
natural (precipitation and temperature patterns) and human-related (air and water pollution)
events that trigger certain responses in the vigor of the tree as seen in its growth rate. In most
geographic regions, climate patterns in any year cause a response by trees in the volume of wood
the tree produces, and often leave indelible “fingerprints” in certain physical and chemical
properties of the wood. These “fingerprints” can be seen in the varying widths of tree rings from
year to year. In some years, climate conditions may be generally unfavorable for tree growth,
causing a reduction in the volume of wood produced. On a cross section of wood, this reduced
growth will appear as tree rings that are narrower than normal (Figure 1, ring A compared to the
ring B). In other years, environmental conditions may be favorable for tree growth, allowing
trees to produce greater volumes of wood. When viewed as a cross section through the trunk of
the tree, the greater volume of wood will appear as wider than normal tree rings (Figure 1, ring C
compared to ring B). These patterns of narrow and wide tree rings that accumulate over many
years during the lifetime of the tree make tree-ring dating possible.
A tree grows by forming a new sheath or layer of woody tissue each year just underneath
the bark, much like a stack of cones one on top of the other. This growth occurs in a thin layer of
cells that completely shrouds the tree just inside the bark called the vascular cambium. Here,
cambial cells divide, with outer cells contributing to the formation of phloem, and inner cells
contributing to the formation of woody tissue. In temperate and subpolar regions, most trees
break from winter dormancy and begin growth by forming new cells of wood using nutrient
reserves stored from the previous growing season. In conifer trees, these cells are large, less
Tree-Ring Dating of a Panel Painting
Page 3
dense, and have thin walls, producing light-colored wood called earlywood (Figure 1). Toward
the end of the growing season, before the tree begins its dormancy period, smaller, denser, thickwalled cells are formed that are darker in color and called latewood (Figure 1). Taken together,
these two bands of wood form an annual tree ring. In certain hardwoods, such as oaks, large cells
called vessels are formed in the earlywood, while the latewood often lacks such vessels.
ASSIGNING CALENDAR YEARS TO TREE RINGS BY CROSSDATING
Crossdating is the primary guiding principle and technique in dendrochronology, and
concerns the matching of patterns of ring widths from one tree with corresponding patterns for
the same years from another tree. Eventually, sequences from individual trees are combined into
a reference chronology for any particular location, so that any new tree-ring samples collected
can immediately be crossdated against the reference chronology. Crossdating is possible because
climate is largely a regional phenomenon, affecting trees within a geographic region in a like
manner, so that similar patterns of ring widths are produced among many trees. A unique pattern
of wide and narrow rings formed during a 50-year period is unlikely to be formed during any
other 50-year period because climate varies from year to year. Furthermore, crossdating helps
identify problematic rings, such as false rings (a dark band of cells within the ring that is not a
true ring), and helps identify locally absent or discontinuous rings (produced when growth
regulators do not reach certain points in the trunk of the tree).
Crossdating is initially accomplished with graphical comparisons that accentuate the
importance of patterns of wide and narrow rings. The pattern of rings is matched, or crossdated,
against a reference chronology until a firm match is found (Figures 2A and 2B). The tree-ring
widths are then measured, and the crossdating accuracy is statistically confirmed using computer
Tree-Ring Dating of a Panel Painting
Page 4
software. To ensure a high level of confidence in the dates assigned to tree rings,
dendrochronologists look for high levels of statistical significance, higher than those normally
used in statistics to identify a probable match. Only after a tree-ring series has been crossdated
precisely, both graphically and statistically, can dates for the tree rings in a wood sample be
assigned.
TREE-RING DATING OF PANEL PAINTINGS: A SHORT HISTORY
Tree-ring dating techniques have been used since the early years of the 20th century to
determine the years of construction of historic sites throughout the United States and Europe.
Andrew Ellicott Douglass, the founder of dendrochronology, first used tree-ring dating to help
solve one of prehistoric archaeology’s most vexing questions: When where the pueblos of the
American Southwest built? Prior to tree-ring dating, such historic structures were dated by
ceramic styles but no firm technique had been developed that placed these structures in exact
historical time. Douglass worked for over 15 years between 1914 and 1929 to solve this mystery
and finally was able to determine the exact years of construction for 25 famous archaeological
sites throughout the Southwest (Douglass 1921, 1929). Interestingly, most of the famous pueblo
sites in the American Southwest were actually several hundred years younger than archaeologists
had originally thought.
It wasn’t long before scientists recognized the potential of tree-ring dating on other
objects and structures made of wood. Several conditions are required for tree-ring dating to work
successfully, however. First, the wood used to make the object must have distinct rings. Some
species of trees do not form distinct rings while others form erratic ring patterns that can not be
dated. Second, the object must have enough rings to provide a conclusive match with other
Tree-Ring Dating of a Panel Painting
Page 5
samples. In general, dendrochronologists like to have a strong statistical match between two
chronologies that covers at least 70 to 80 years, although actual matches often cover many more
years (greater than 100 or even 200 years). Shorter sequences of tree rings often are problematic
to date. Third, a reference chronology must be available for the region from which the tree grew
that was eventually crafted into an object or made into a structure. Without a reference
chronology, the object can not be dated.
In 1970, tree-ring scientists from the University of Hamburg first applied tree-ring dating
techniques to verify the year of attribution for paintings on panels. Bauch and Eckstein (1970)
analyzed the panels on 17th century paintings made by several Dutch masters: Philips
Wouverman (1619–1668), Klaes Molenaer (1630–1676), and Cornelius Dusart (1660–1704).
Bauch and Eckstein proved that tree-ring patterns matched significantly between different panels
from the same painting as well as between different paintings, firmly establishing the possibility
of developing reference chronologies to date other panel paintings. Second, Bauch and Eckstein
were able to show that the dates for the outermost tree rings on these panels supported the
attributed years the paintings were made. In other words, the outermost tree-ring dates had to
pre-date the year the painting was supposedly created. This demonstrated the possibility that
tree-ring dating could be used to help authenticate the year in which a painting was made,
although tree-ring dating can not provide the actual year the painting was made. The technique
only provides the year after which the painting could have been made. More importantly, this
initial study showed how tree-ring techniques could potentially isolate fakes and copies of
famous works, although none were found in this first study. Should the year for the outermost
ring post-date the year the painting was made, then the painting is likely a fake or copy.
Tree-Ring Dating of a Panel Painting
Page 6
Bauch and Eckstein (1981) later analyzed 150 panels from paintings accepted or not
accepted as authentic Rembrandts and Rembrandt associates, provided by the Rembrandt
Research Group in Amsterdam. In all cases, the outermost ring on these panels pre-dated the
attributed date for all paintings, even after the number of additional rings were estimated and
placed on the outside of the outermost ring. This procedure of estimating additional rings on the
outside is necessary because wood craftsmen would remove some or all of the sapwood from the
oak used to make the panels when squaring the wood. Bauch and Eckstein cautioned, however,
that tree-ring dating limit itself to the determination of the outermost (youngest) tree ring without
any further interpretations, “which should be reserved to the art-historian.”
Nearly simultaneous with the researchers from the University of Hamburg, a scientist at
Oxford University in England began a systematic analysis of the tree-ring dates from panel
paintings to again verify the reported attribution dates for famous paintings, but also wished to
determine the source region of the wood used to make the panels. Fletcher (1973, 1976, 1977)
developed some the longest tree-ring reference chronologies from archaeological art-historical
objects ever, nearly all of which are in use to this day. Fletcher was able to show how the tree
rings on panels in many paintings could actually be traced to a certain geographic region of
Europe. This would greatly aid the crossdating process by creating a smaller subset of reference
chronology to which the tree rings being tested would be crossdated.
Approximately 80 studies have since been published that used tree-ring dating techniques
to analyze the rings on panels from famous paintings (see Appendix1, which lists all 80 studies).
These include the many studies by Dr. Peter Klein, also of the University of Hamburg, who
elevated the science by analyzing the panels on many famous paintings, such as those made by
Rogier van der Weyden (Klein 1981), Jean Fouquet (Klein 1984), Lucas Cranach the Elder
Tree-Ring Dating of a Panel Painting
Page 7
(Klein 1986), Raphael (Klein and Bauch 1990), Petrus Christus (Klein 1994a), Lucas Cranach
(Klein 1994b), Hieronymus Bosch (Klein 1996a), and Tom Ring (Klein 1996b). Klein was
instrumental in helping art historians revise their interpretations of famous works of art, such as
the triptych by Rogier van der Weyden (The Nativity, The Pietà and Christ Appearing to His
Mother) (Figure 3). Art historians had previously thought that the original was displayed in
Capilla Real, Granada (left and middle panels) and the Metropolitan Museum of Art in New
York (right panel), while a copy was displayed in the Staatliche Gemaldegalerie Berlin-Dahlem.
(Klein 1986) showed instead, using tree-ring dating, that the Berlin-Dahlem has the early
original painting while New York and Granada have a “posthumous copy” (Kuniholm 2000)
In addition to the concentration of such studies in Germany and England, tree-ring
research on panels has also been conducted in Italy by Professor Elio Corona (Corona 1984,
1994), in Denmark by Dr. Niels Bonde (Bonde et al. 1993), in France by Dr. Catherine Lavier
and Dr. Georges Lambert (Lavier and Lambert 1996), in the Netherlands by Dr. Esther Jansma
(Jansma et al. 2004), and in Belgium by Dr. Patrick Hoffsummer (Hoffsummer 1989). In the
United States, Dr. Peter I. Kuniholm from Cornell University, has been involved in the tree-ring
dating of panels from paintings (Kuniholm 2000).
Key among these latter studies (and very relevant to this study) is that study conducted by
Dr. Jennifer Hillam and Dr. Ian Tyers of Sheffield University and the Museum of London,
respectively (Hillam and Tyers 1995). These researchers first conducted independent crossdating
analyses on 177 sets of tree-ring measurements first developed by Dr. John Fletcher at Oxford
University obtained from panel paintings to test the veracity of the original datings. Hillam and
Tyers concluded that their analyses revealed “a high level of agreement between the [two]
laboratories,” suggesting correct temporal placements of the 177 series. However, the authors
Tree-Ring Dating of a Panel Painting
Page 8
also concluded that one of the original temporal placements obtained by Fletcher was incorrect.
The painting Virgin and Child by Jan Mabuse (ca. 1478–1532) that Fletcher had classified a fake
was in fact probably genuine. In addition, 49 panels that Fletcher had dated previously could not
be dated by either of the two laboratories. This conclusion concerning the veracity of some of
Fletcher’s earlier datings can be attributed to new technologies used in tree-ring dating in the
1980s and 1990s, particularly computer-assisted statistical crossdating (see Holmes 1983 and
Grissino-Mayer 2001) which revolutionized tree-ring dating.
Perhaps the most important outcome of this study was the recognition of two major
source regions for the oak timbers used in these 177 panels. Based on the strength of the
crossdating among the tree-ring series, Hillam and Tyers were able to develop two reference
chronologies from this larger data set: “Baltic 1” consists of tree-ring sequences from 67 panels
and spans AD 1156 to 1597, while “Baltic 2” consists of tree-ring sequences from 40 panels and
spans AD 1257 to 1615. The differences between the two chronologies could be attributed to
changes in source regions for the oak timbers, which had to be imported from the region
surrounding the eastern Baltic Sea region. This change in the source region could reflect
fluctuations in exports from different ports (Hillam and Tyers 1995) caused by changing
numbers of trees available for harvesting.
Our study will rely extensively on the use of the “Baltic 1” reference chronology, which
was kindly supplied by Dr. Ian Tyers, now with the University of Sheffield. Oak trees were often
imported from this region to supply wood for art objects and artists working in western Europe
(Baillie 1984; Wazny 1992, 2002; Klein 1998; Jansma et al. 2004), while wood from Germany
was used mostly to make furniture (Jansma et al. 2004). The “Baltic 1” reference chronology
consists of 98 dated series and spans from A.D. 1167 to 1597 but was recently extended by
Tree-Ring Dating of a Panel Painting
Page 9
Dutch researchers out to A.D. 1637 (Jansma et al. 2004). Artists working in the Netherlands in
this time frame likely would have used wood imported from the Baltic region.
BACKGROUND TO THIS RESEARCH PROJECT
In 2004, the Laboratory of Tree-Ring Science at the University of Tennessee was
contacted by an individual to evaluate the potential of our using tree-ring dating techniques on a
panel painting that was believed by the owner to have to have been painted by Rembrandt van
Rijn (1606–1669) (Figure 4). We had not previously been involved in the dating of panel
paintings, but we had considerable experience dating the tree rings on wood from musical
instruments and on logs from historical structures. Our primary objective was to determine the
exact range of years for the tree rings found in the panels of this painting. The process consisted
of first measuring the widths of all tree rings found in the panels, then comparing the pattern of
wide and narrow rings against a reference tree-ring chronology created from many tree-ring
sequences found in other panels on paintings made by well-known painters between the 15th and
17th centuries. The match between the panels being tested from this painting (Figure 4) and the
reference tree-ring chronology had to be convincing both graphically and statistically.
METHODS
Surface Preparation
Both the upper and lower surfaces of each of the three panels were surfaced using
progressively finer polishing film to protect the delicate surfaces of the panels (Orvis and
Grissino-Mayer 2002). Because the painting had to be examined intact, the sanding of the panels
was done solely by hand-sanding (Figure 5). Normally, the sanding process results in a wood
Tree-Ring Dating of a Panel Painting
Page 10
surface with cellular features clearly defined under 10x magnification for clear ring
identification. We noticed, however, that only the middle panel of the three panels had rings that
could be clearly defined along the entire surface from one end to the other. Other techniques,
such as planing the panel surfaces flat followed by calcium carbonate pressure infusion, were
considered too invasive and potentially damaging, and were not used in this project.
Once sanded, we used a jeweler’s loop to count all rings and marked with a lead pencil
each decade ring according to established convention: one dot for each decade ring (e.g., rings
10, 20, and 30), two dots for each 50th ring (e.g., rings 50 and 150), and three dots for each
100th ring (e.g., rings 100 and 200) (Stokes and Smiley 1996). Special care was given to ray
features common in oak wood (and other ring-porous hardwood tree species) that often can
divide an individual ring in two and appear to offset on either side of the ray (Baillie 1982),
which would result in inaccurate ring counts and errors in assigning absolute calendar years to all
tree rings.
Obtaining Tree-Ring Measurements
We then measured the widths of all tree rings on all panels surfaces to 0.01 mm accuracy
with a Velmex measuring stage coupled with MEASURE J2X software running on a Pentium
personal computer. A special adaptation had to be added to the measuring stage to ensure
measurement of the transverse surface of the rings. We constructed a vise-like device that would
firmly hold the entire painting upright from the bottom (Figure 6). A stereozoom boom-arm
microscope was then placed over the painting, on which was attached a color CCD camera
through the ocular of the microscope (Figure 7). This arrangement allowed measurements to be
captured without having to peer through the microscope at an awkward height. The image of the
Tree-Ring Dating of a Panel Painting
Page 11
panel surface with the tree rings was then projected onto a 21 inch color monitor. The widths of
the tree rings were measured by turning the movable stage (on which the newly-devised
apparatus firmly held the painting) from the beginning of one tree ring to the beginning of the
next tree ring. Because the Velmex stage sat on the floor, one person slowly turned the stage (to
avoid unnecessary movement of the painting) while another person instructed when to start and
stop the movement of the stage.
Because the dates of the tree rings are unknown, the ring series are considered “floating”
in time (Bannister 1962) and therefore we assigned the year “1” to the first complete tree ring in
each series and measured subsequent rings sequentially. To ensure all tree rings were identified,
we measured the widths of the tree rings on the panels twice. All tree-ring measurements were
captured and archived in internationally-accepted Decadal format as recognized by the
International Tree-Ring Data Bank, part of the National Climatic Data Center and World Data
Center for Paleoclimatology in Asheville, North Carolina. The accuracy of our measurements
(0.01 mm) would be considered exceptional by art history standards because many previous
studies simply used a hand lens or 10X eye piece to inspect the widths of tree rings on famous
panel paintings and other art historical objects. Some studies assigned an “index” of ring width to
individual rings (Jansma et al. 2004) while other studies measured the ring width to the nearest
0.1 mm (Fletcher 1977) rather than obtaining more accurate absolute measurements as we
accomplished in our study.
The Baltic 1 Reference Chronology
Absolute dating was accomplished by comparing the pattern of wide and narrow rings
from our floating tree-ring chronology obtained from the panels with an anchored reference tree-
Tree-Ring Dating of a Panel Painting
Page 12
ring chronology developed by members of the University of Sheffield Dendrochronology
Laboratory (see http://www.shef.ac.uk/archaeology/research/dendrochronology). On April 21,
2006, we contacted Dr. Ian Tyers of this laboratory and inquired about the availability of the
“Baltic 1” and “Baltic 2” reference chronologies that were developed in 1995 (Hillam and Tyers
1995). Dr. Tyers was very enthusiastic about our using these data sets and immediately sent both
reference chronologies to the Laboratory of Tree-Ring Science at the University of Tennessee.
These are included in Appendix 2A (“Baltic 1”) and Appendix 2B (“Baltic 2”). The reference
chronologies had recently been used in a monumental study conducted by the Netherlands
Centre for Dendrochronology, a laboratory of the Netherlands’ National Service for
Archaeological Heritage Management, stationed in Amersfoort, the Netherlands (Jansma et al.
2004). The Dutch researchers analyzed numerous objects currently housed in museums in the
Netherlands (including the Rijksmuseum in Amsterdam), including panel paintings, sculptures,
cabinets, chests, desks, and tables, among other items, which yielded 159 individual dated series.
Graphical Crossdating
The comparison of ring patterns between two tree-ring data sets is known as crossdating
and is accomplished using both graphical and statistical crossdating techniques (Swetnam et al.
1985; Stokes and Smiley 1996; Grissino-Mayer 2001). Initial crossdating via graphical
techniques is first attempted by creating a “skeleton plot” of the ring patterns from the series
being dated. Such skeleton plots only emphasize the narrow rings in the series because the
narrow tree rings are more diagnostic than are the wider rings, which often exhibit considerable
lack of variability in their widths compared to narrow rings. A second skeleton plot is next
created for the anchored reference tree-ring chronology, over which the plot for the series being
Tree-Ring Dating of a Panel Painting
Page 13
dated is placed. Much like fingerprint matching, the skeleton plot of the series being dated is then
slid, one year at a time, down the skeleton plot created from the reference chronology until the
majority of lines (indicating narrow rings) on the two plots line up to ensure correct temporal
placement.
The alignment of the skeleton plots was tested statistically used a non-parametric
technique called a chi-square analysis (Burt and Barber 1996), used by Grissino-Mayer et al.
(2004) to help date the famous “Messiah” violin. This analysis uses a 2 X 2 contingency table
based on matches between wide and narrow rings between the two skeleton plots. The table
consists of four cells labeled A, B, C, and D (Figure 8). “Test series” is the tree-ring series that is
being dated (in this case, from the panels of the painting), while “Reference series” is the
reference chronology (here, the “Baltic 1” chronology). Rings are evaluated as being wide or
narrow for both series. If the two series are aligned correctly, then the wide and narrow rings
should match up between the two, in the A (wide and wide on both = match) and D (narrow and
narrow on both = match) cells. Mismatched rings will occupy cells B (narrow versus wide =
mismatch) and C (wide versus narrow = mismatch). The “actual” number of matches or
mismatches is placed in each cell, along with the “expected” number in each cell, from which the
chi-square statistic is generated:
X2
(fij – Fij)2
= ∑ ∑ ––––––––
i=1 j=1
Fij
r
c
where fij is the actual number of matches or mismatches in cell “ij” (row i, column j) and Fij is
the expected number of matches or mismatches in cell “ij”. The calculated X
2
statistic is then
compared to the critical X 2 statistic based on (r – 1)(c – 1) degrees of freedom, where r is the
Tree-Ring Dating of a Panel Painting
Page 14
number of rows and c is the number of columns (two each in a 2 X 2 table, or 1 degree of
freedom). If the calculated X 2 value is greater than the critical value, then we reject the null
hypothesis that states that no relationship exists between the two series (i.e., the two series are
independent and do not date against each other at this temporal placement). We then accept the
alternate hypothesis that the two series are indeed “dependent” on each other and that a
significant relationship exists between the two series at this dated position. Our chi-square
analysis was performed in Microsoft Excel (function “CHITEST”) and verified using the online
chi-square calculator at the University of Illinois Urbana–Champaign’s Statistical Computing
Instruction Laboratory (see http://www.stat.uiuc.edu/courses/stat100/java/chisquare/ChiSquareApplet.html).
A second graphical technique we used in this project uses common X-Y line plots,
created in Microsoft Excel, in which the series being tested is again slid down the line plot of the
anchored series one year at a time until the two plots line up. At each position, a correlation
coefficient (r-value) is calculated that shows the strength of the agreement between the two series
(the panels being tested and the reference anchored tree-ring chronology). Correlation
coefficients are easily calculated in Excel using the “CORREL” function which returns r-values
between –1 and +1. A value near –1 indicates an inverse relationship between two series; in
other words, as the value for any one year goes up on one series, the value for that same year
goes down on the other series. A positive r-value indicates that as the value for any one year for
one series goes up (or down), the value for the other tree-ring series also goes up (or down) in a
similar manner. Tree-ring dating is only concerned with positive r-values. The r-value is
calculated as:
Tree-Ring Dating of a Panel Painting
Page 15
where n is the number of years in common between the two tree-ring series, x is a value for the
first series in any given year, and y is the value for the second tree-ring series in that same year.
In this study, we compared the line graph created from the ring measurements of Panel 2
with the line graph created from the Baltic 1 reference chronology made available by the
University of Sheffield Dendrochronology Laboratory. In addition, we compared the line graph
from Panel 2 with a line graph created from the Netherlands Baltic reference chronology made
available by the Netherlands Centre for Dendrochronology and listed in Jansma et al. (2004).
Correlation coefficients were computed between Panel 2 and the Baltic 1 and Netherlands Baltic
reference chronologies. If crossdating could be achieved solely for Panel 2, then the chances of
dating Panels 1 and 3 would improve.
Statistical Crossdating
We confirmed the initial graphical crossdating and relative placements of the tree-ring
series being tested using COFECHA, a quality-control program that uses segmented time-series
correlation techniques to confirm the temporal placements of all tree rings (Holmes 1983).
Because crossdating is essentially a “high-frequency” process (pattern matching of sequences of
individual rings), COFECHA removes all low-frequency trends using both spline-fitting
algorithms and autoregressive modeling (Cook and Peters 1981, Cook 1985, Grissino-Mayer
2001). Such trends could also arise due to natural and human disturbances that otherwise could
mask the (common) climate signal desirable for accurate crossdating. COFECHA then tests
Tree-Ring Dating of a Panel Painting
Page 16
consecutive 50-year segments from each series with a temporary master chronology created from
all other measurement series. In this analysis, we tested 50-year segments with a 10-year lag to
refine our crossdating and help identify problem area in the ring sequences. In Other words, we
first tested rings 1–50, then rings 11 through 60, then rings 21 through 70, until the end of the
series was reached, comparing these segments with an average from the same segments created
from the remaining series. Crossdating is verified when the correlation coefficient for each tested
segment in each series being tested exceeds 0.37 (p < 0.01), although coefficients for segments
from undated series are usually higher. The final placement made by COFECHA had to be
convincing graphically (similar patterns in wide and narrow rings) and statistically (highly
significant correlation coefficients). Once confirmed, we assigned absolute years to all individual
rings in each measurement series being tested.
RESULTS
Panel 1 (left panel, facing the painting) was found to measure 8 1/16 x 35 in (20.5 x 88.9
cm) and contained 206 rings. Panel 2 (middle panel) measured 9 9/16 x 35 in (24.3 x 88.9 cm)
and contained 217 rings. Panel 3 (right panel) measured 10 3/8 x 35 in (26.4 x 88.9 cm) and
contained 197 rings. Each panel was approximately (0.25 in) 6 mm thick. All measurements
from the three panels are provided in Appendices 3A (Panel 2), 3B (Panel 1), and 3C (panel 3).
Original Position of the Panels
The oak rings on the panels could easily be discerned once the surfaces were polished to
a high degree (Figures 9-1, 9-2, and 9-3). Panel 1 (towards the left facing the painting) showed
significant curvature in the innermost rings of the surface (Figure 9-1), which always indicates a
Tree-Ring Dating of a Panel Painting
Page 17
panel that was cut to one side of the center of the log, called a “tangential cut” (see Figure 10 b).
Because of this curvature, special care had to be taken when measuring because the ray cells that
emanate from the center of the oak tree can cause rings to become offset on either side of the ray.
Panel 2 (the middle panel) had by far the clearest sequences of tree rings of the three panels.
More importantly, the rings on this panel were nearly all perpendicular to the cut of the wood
and all ray cells were aligned parallel to the panel, when visible. This can be clearly seen in
Figure 9-2. Hence, the ray cells were not problematic in this panel. The alignment of rings and
cellular features strongly suggests that this panel was cut nearly centered towards the pith
(center) of the log, called a “radial cut” (see Figure 10a). Panel 3 (towards the right as one faces
the painting) displayed features that suggested an intermediate location inside the log between
panels 1 and 3. Nearly all the tree rings are tilted at an angle to the panel (Figure 9-3), but do not
display the extreme curvature seen in Panel 1. In addition, the ray cells also cut across the
surface of the panel at an angle causing many rings to become offset (see red circle areas in
Figure 9-3).
In general, based on the lack of curvature in the rings, Panel 2 is the highest quality panel
for dating purposes for this project. Panel 1 had a good chance of being dated accurately, while
the tree rings from Panel 3 posed the most problems for dating.
Graphical Crossdating
Because Panel 2 had the clearest ring sequences that we felt were the most reliable, we
created a skeleton plot from the measurements and slid this plot down a skeleton plot created for
the Baltic 1 master chronology one year at a time until a clear match occurred. We found a very
good match that clearly showed ring 1 on Panel 2 as being the year AD 1369 while ring 217 on
Tree-Ring Dating of a Panel Painting
Page 18
Panel 2 was the year AD 1585 (Figure 11). Because trees are individualistic, based on their
immediate surroundings, scientists rarely expect tree-ring sequences to be perfectly aligned. We
look for matches in the narrowest of rings (for example, rings 35–36, 51–52, 50, 55, 95, 102, and
111 on the upper series from Panel 2, Figure 11) as well as matches in clusters of rings (for
example, rings 124–131, 198–203, and 213-216 on the upper series from Panel 2, Figure 11).
This was by far the best match between the two series.
The chi-square analysis also substantiated the temporal placement of AD 1369–1585 for
Panel 2 as being the most likely dated position. The analysis of the skeleton plots revealed 76
wide-wide matches and 68 narrow-narrow matches (total 144 matches) versus only 72
mismatches (28 narrow-wide and 44 wide-narrow). Expected values in each cell (indicating
randomness, or no association between the two series) were: Cell A: 58, Cell B: 46, Cell C: 62,
and Cell D: 50. The chi-square statistic (X 2) was 24.335 which had a probability (p-value) of
less than 0.005, meaning that a X 2 of this value has less than a 5 in 10,000 chance (1 in 2,000) of
occurring simply by chance. In other words, we have a confidence level greater than 0.995 (1
minus 0.005), or > 99.5% confidence, that we have found the correct temporal position for the
tree rings in Panel 2, based on the chi-square analysis.
The suggested temporal position of AD 1369 to 1585 was again confirmed by the
alignment of the line graphs for Panel 2 versus the Baltic 1 reference chronology (Figure 12A)
and versus the Netherlands Baltic reference chronology (Figure 12B). These graphs showed
coherency in both the year to year variation (high frequency variation) and decadal-scale
variation (low frequency variation). The common patterns in the low-frequency variation is very
convincing. For example, in both the measurements for Panel 2 and the Baltic 1 reference
chronology (Figure 12A), the values decline steadily between A.D. 1375 and 1425, then steadily
Tree-Ring Dating of a Panel Painting
Page 19
increase between 1425 and 1440. Between 1440 and 1490, both series again decline steadily
followed by a gradual increase in values until A.D. 1515. Both series then decrease again until
about 1530, after which the series appear to diverge. Between A.D. 1560 and 1585, the series
show little similarity in the low-frequency, likely an artifact of low sample size in the Baltic 1
reference chronology. This would explain the very low values seen after A.D. 1560 in the Baltic
1 reference chronology.
Surprisingly, the measurements from Panel 2 show better agreement with the Netherlands
Baltic tree-ring chronology (Figure 12B). The Netherlands data set was created independently
from art historical objects and furniture not analyzed originally by Dr. John Fletcher at Oxford
University, nor analyzed by Dr. Jennifer Hillam and Dr. Ian Tyers of Sheffield University. In
other words, the Netherlands Baltic reference chronology may consist of series of tree-ring
measurements that have much more in common with the tree rings from the oak panels of the
painting being investigated in this study.
The correlation coefficients calculated between Panel 2 and both the Baltic 1 and
Netherlands Baltic reference chronologies further substantiate the temporal placement of A.D.
1369 to 1585 for Panel 2. An r-value of 0.25 (n = 217 years overlap, t-value = 3.79, p < 0.0001)
was found in the comparison with the Baltic 1 reference chronology, while a higher r-value of
0.38 (n = 217 years overlap, t-value = 6.02, p < 0.0001) was found when comparing with the
Netherlands Baltic chronology. These r-values are highly significant with a probability of less
than 1 in 10,000 (p < 0.0001) that these r-values occurred simply by chance.
Tree-Ring Dating of a Panel Painting
Page 20
Statistical Crossdating
We input the measurement series from Panel 2 (found in Appendix 3A) into the computer
program COFECHA as an undated series, and compared it with the dated Baltic 1 reference
chronology. The results from this crossdating attempt would be considered definitive by
dendrochronological standards. COFECHA suggested that 12 of the 18 50-year segments tested
from Panel 2 be adjusted by +1368 (see details in Appendix 4A); in other words, the value 1368
had to be added to all the rings in Panel 2 (with rings numbered 1 through 217) and it would then
be dated against the Baltic 1 reference chronology. This suggests that the rings for panel 2 date to
1369 to 1585, similar to the results obtained in the skeleton plot, line graph, chi-square, and
correlation analyses. The average r-value for the 12 segments was 0.44 at the +1368 adjustment,
which was significantly better than the second best dating adjustment recommended by
COFECHA: 5 segments with a dating adjustment of +1107, and an average r-value of 0.31.
Significant in this analysis is that 7 of the 12 segments that showed this one dating adjustment
dated at the number 1 position, while two other segments dated at the number 2 position (see
Appendix 4A).
To test the efficacy of this dating adjustment, we re-ran COFECHA but this time selected
to test 50-year segments with a 25-year lag rather than a 10-year lag. This is a more rigorous
analysis because fewer segments are now tested. We found that five of the eight 50-year
segments tested again dated at the +1368 dating adjustment (Appendix 4B), similar to the
previous analysis. Three of the segments with the +1368 adjustment dated at the number 1
position while another dated at the number 2 position. This additional analysis confirms that
the tree rings in Panel 2 date to A.D. 1369 to 1585.
Tree-Ring Dating of a Panel Painting
Page 21
We next input the ring measurements from Panel 1 (found in Appendix 3B) in
COFECHA as an undated series and tested 50-year long segments (lagged 10 years) against the
Baltic 1 reference chronology. We found 12 of the 17 50-year segments tested all showed a
common dating adjustment of +1337 (Appendix 5A). The strength of this crossdating is further
shown by the five consecutive segments for rings 91 through 180 that dated in the number 1
position, with another 2 segments dating in the number 2 position. These 12 segments had an
average r-value of 0.39 which was higher than the average r-value (0.35) for the second best
dating adjustment of +1396 based on 7 segments. These results show that the tree rings on
Panel 1 date from A.D. 1338 to 1543. The earlier innermost ring on this panel relative to Panel
2 (A.D. 1369) is substantiated by the curvature of the rings on this panel which indicate the panel
was cut close to the pith of the log. We again ran COFECHA but this time we tested 50-year
segments lagged 25 years rather than 10 years, and found four of seven 50-year segments dated
at the +1337 adjustment (Appendix 5B).
We next input the measurements from Panel 3 into COFECHA as an undated series and
compared it to the Baltic 1 reference chronology. Panel 3 was our most problematic panel to
measure because of the propensity of offset rings caused by ray cells that were angular to the
panel surface (see Figure 9-3). Although we feel that we accounted for all the rings despite the
offsets, the widths of our measurements may not be as accurate as could be because of the angle
of the rings near the offsets caused by the ray cells. The top three dating adjustments suggested
by COFECHA were: (1) +1205, 7 segments, average r-value = 0.35, (2) +1223, 6 segments,
average r-value = 0.40, and (3) +1392, 6 segments, average r-value = 0.45 (Appendix 6A). The
+1205 dating adjustment is not convincing because it is not found in the number one suggested
position, and only shows up once in the number two position. The +1223 adjustment shows up
Tree-Ring Dating of a Panel Painting
Page 22
once in the number one position and 4 times in the number 2 position, all consecutive, which is
only somewhat convincing. Of these, the third dating adjustment is the most convincing because
of the very high average r-value of 0.45 based on six segments tested out of 16 total segments. In
addition, three segments dated at the number one position, and another at the number 2 position,
all consecutive. These findings suggest that this panel may have tree rings that date from A.D.
1393 to 1589, but one additional crossdating attempt was warranted.
We then tested the tree rings of this panel against the tree-ring patterns on the other two
dated panels, again using COFECHA. This is a common strategy when attempting to date
floating tree-ring series. If the reference tree-ring chronology yields inconclusive results (which
occasionally happens), then dendrochronologists try dating the floating series against individual
dated measurement series. The assumption here is that the individual dated series will likely
represent a tree from the same vicinity as the tree for the floating series. In this analysis, we input
the dated measurements from Panel 1 and then Panel 2 into COFECHA as the dated series. The
most significant result for Panel 3 was found in its comparison with the tree rings from Panel 1
(Appendix 6B). In fact, this result can be considered conclusive. We found that 11 of the 16 50year segments tested showed a similar dating adjustment of +1392 with an average r-value of
0.45. More importantly, seven of these segments dated at the number 1 position in consecutive
order, representing rings 21 through 130, indicating a strong match. The second best dating
adjustment was +1320, based on six segments, with an average r-value of only 0.26. These
results strongly show that the tree rings for Panel 3 date from A.D. 1393 to 1589.
Tree-Ring Dating of a Panel Painting
Page 23
CONCLUSIONS
This project was conducted on oak panels from a painting possibly made by a Dutch
master, although the tree-ring aspect of this project certainly can not tell who exactly the painter
was. This situation, however, is common for virtually all objects dated by tree-ring analyses –
dendrochronologists can date the tree rings and provide precise dates for the range of years
represented in a wooden object, but dendrochronologists can never prove who the painter or
creator of the wooden object was. Still, dendrochronology and archaeology together can help
provide information useful to experts who wish to assign a painter or maker to a wooden object.
For example, when was the tree (or trees) cut that was used to make the panels used in
the painting? First, we have an outermost date on any of the three panels of A.D. 1589 (Panel 3).
Second, no sapwood was present on any of the three panels, as is expected because sapwood is
less dense and decays more rapidly than the denser heartwood found on oak. We can assume for
the time being that the outermost ring was near the sapwood/heartwood boundary on Panel 3 (see
Figure 10d). Klein (1993) estimated that 15 years +4/–2 years should be added to the outermost
ring found on Baltic oaks used in wooden objects. This would place the outermost ring on the
living tree when it was harvested at A.D. 1601 (range A.D. 1599 to 1605).
Finally, the estimate must again be modified to account for seasoning of the wood.
Freshly cut trees contain a large amount of moisture in their wood, and paint does not adhere to
wet wood (Kuniholm 2000). Therefore, the wood had to be left to air-dry (season) for a number
of years before it could be used as a backing for a painting. Bauch and Eckstein (1970) observed
that the difference between dated paintings and their outermost rings were 5 years ±3 years.
Using the previous sapwood estimates, this would place the outermost rings at A.D. 1604 to
1610, with a range from A.D. 1601 to 1613. This range of years represents the earliest years of
Tree-Ring Dating of a Panel Painting
Page 24
tree harvest that may be represented on the three panels based on the outermost ring on Panel 3.
However, because we observed no sapwood/heartwood contact zone (see Figure 10a), we can
also assume that some heartwood rings may have been trimmed off during the shaping process
(Kuniholm 2000), pushing the date for tree harvest even later. No means exists, though, to
estimate the number of heartwood rings that may have been trimmed off.
Whoever painted this masterpiece lived and painted in the early to mid-1600s. The
analyses performed in our laboratory support its possible attribution to Rembrandt van
Rijn.
Tree-Ring Dating of a Panel Painting
Page 25
REFERENCES CITED IN THIS STUDY
Baillie, M.G.L. 1982. Tree-Ring Dating and Archaeology. University of Chicago Press, Chicago.
274 pp.
Baillie, M.G.L. 1984. Some thoughts on art-historical dendrochronology. Journal of
Archaeological Science 11: 371–393.
Bauch, J., and D. Eckstein. 1970. Dendrochronological dating of oak panels of Dutch
seventeenth-century paintings. Studies in Conservation 15: 45–50.
Bauch, J., and D. Eckstein. 1981. Wood biological investigations on panels of Rembrandt
paintings. Wood Science and Technology 15: 251–263.
Bannister, B. 1962. The interpretation of tree-ring dates. American Antiquity 27: 508–514.
Bonde, N., T. Bartholin, K. Christensen, A. Daly, and O.H. Eriksen. 1993. Dendrokronologiske
dateringsundersogelser pa Nationalmuseet 1992. Arkæologiske udgravninger i Danmark:
305–321.
Burt, J.E. and G.M. Barber. 1996. Elementary Statistics for Geographers, 2nd edition. Guilford
Press, New York. 640 pp.
Cook, E.R. 1985. A time series analysis approach to tree ring standardization. Ph.D. dissertation,
University of Arizona, Tucson, Tucson, AZ. 171 pp.
Cook, E.R., and K. Peters. 1981. The smoothing spline: a new approach to standardizing forest
interior tree-ring width series for dendroclimatic studies. Tree-Ring Bulletin 41: 45–53.
Corona, E. 1984. Il supporto ligneo della Pala di Monteluce. Bollettino dei musei e gallerie
pontificie 5: 137–151.
Corona, E. 1994. Sulla caratterizzazione dei manufatti lignei: opere pittoriche. Italia Forestale e
Montana 49(4): 401–412.
Tree-Ring Dating of a Panel Painting
Page 26
Douglass, A.E. 1921. Dating our prehistoric ruins: how growth rings in trees aid in establishing
the relative ages of the ruined pueblos of the Southwest. Natural History 21(1): 27–30.
Douglass, A.E. 1929. The secret of the Southwest solved by talkative tree rings. National
Geographic Magazine 56(6): 736–770.
Fletcher, J.M. 1973. European dendrochronology and C-14 dating of timber. Pages 9–27 in T.
Watkins, ed., Radiocarbon: Calibration and Prehistory. Edinburgh University Press,
Edinburgh.
Fletcher, J.M. 1976. A group of English royal portraits painted soon after 1513. A
dendrochronological study. Studies in Conservation 21: 171–178.
Fletcher, J. 1977. What wooden panels can reveal. Conservator 1: 12–16.
Grissino-Mayer, H.D. 2001. Evaluating crossdating accuracy: A manual and tutorial for the
computer program COFECHA. Tree-Ring Research 57(2): 205–221.
Grissino-Mayer, H.D., P.R. Sheppard, and M.K. Cleaveland. 2004. A dendroarchaeological reexamination of the “Messiah” violin and other instruments attributed to Antonio
Stradivari. Journal of Archaeological Science 31(2): 167–174.
Hillam, J., and I. Tyers. 1995. Reliability and repeatability in dendrochronological analysis: tests
using the Fletcher archive of panel-painting data. Archaeometry 37(2): 395–405.
Hoffsummer, P. 1989. La dendrochronologie des panneaux peints. L’exemple d’un plafond peint
par Damery à Alden Biesen. Bulletin de l'Institut archéologique liégois 101: 33–47.
Jansma, E., E. Hanraets, and T. Vernimmen. 2004. Tree-ring research on Dutch and Flemish art
and furniture. Pages 139–146 in E. Jansma, A. Bräuning, H. Gärtner, and G. Schleser,
eds., Tree Rings in Archaeology, Climatology and Ecology, Volume 2. Proceedings of the
Dendrosymposium 2003. Schriften des Forschungszentrum Jülich, Reihe Umwelt 44.
Tree-Ring Dating of a Panel Painting
Page 27
Klein, P. 1981. Dendrochronologische Untersuchungen an Eichenholztafeln von Rogier Van der
Weyden. Jahrbuch der Berliner Museen 23: 113–123.
Klein, P. 1984. Dendrochronological studies on panels by Jean Fouquet (1415/20–1477/81).
Pages 25–26 in ICOM, Committee for Conservation, Seventh Triennial Meeting,
September 1984, Copenhagen.
Klein, P. 1986. Age determinations based on dendrochronology. Pages 225–237 in R. van Shoute
and H. Verougstraete-Marcq, eds., Scientific Examination of Easel Paintings. Journal of
the European Study Group on Physical, Chemical, Biological and Mathematical
Techniques Applied to Archaeology (PACT) 13.
Klein, P. 1993. Dendrochronological analysis of German panels in the National Gallery of Art.
Pages 195–197 in J.O. Hand and S.E. Mansfield, eds., German Paintings of the Fifteenth
through Seventeenth Centuries. National Gallery of Art, Washington, D.C., and
Cambridge University Press, Cambridge.
Klein, P. 1994a. Dendrochronological analysis of panels attributed to Petrus Christus. Pages
213–215 in Petrus Christus, Renaissance Master of Bruges. Metropolitan Museum of
Art, New York.
Klein, P. 1994b. Lucas Cranach und seine Werkstatt. Holzarten und dendrochronologische
Analyse. Pages 194–200 in C. Grimm, J. Erichsen, and E. Brockhoff, eds., Lucas
Cranach. Ein Maler-Unternehmer aus Franken. Veröffenlichungen zur Bayerischen
Geschichte und Kultur 26.
Klein, P. 1996a. Dendrochronolgicky pruzkum deskovych obrazu Hieronyma Bosche a jeho
nasledovniku. Pages 54–59 in O. Kotkova, ed., Hieronymus Bosch – nasledovnik:
Tree-Ring Dating of a Panel Painting
Page 28
Dvanactilety Jezi v chramu. Obraz po zrestaurovani. Nationalgalerie, Prague, Czech
Republic.
Klein, P. 1996b. Dendrochronologische Untersuchungen an Gemäldetafeln der Malerfamilie
Tom Ring. Pages 212–215 in A. Lorenz, ed., Die Maler Tom Ring. Westfälisches
Landesmuseum für Kunst und Kulturgeschichte, Münster, Germany.
Klein, P. 1998. Dendrochronological analyses of panel paintings. In: K. Dardes, ed., The
Structural Conservation of Panel Paintings: Proceedings of a Symposium at the J. Paul
Getty Museum. Oxford University Press, Oxford: 39–54.
Klein, P., and J. Bauch. 1990. Analyses of wood from Italian paintings with special reference to
Raphael. Pages 85–91 in J. Shearman and M.B. Hall, eds., The Princeton Raphael
Symposium 1983. Princeton University Press, Princeton, New Jersey.
Kuniholm, P.I. 2000. Dendrochronology (tree-ring dating) of panel paintings. Pages 206–226 in
W.S. Taft, Jr., and J.W. Mayer, eds., The Science of Paintings. Springer Verlag, New
York.
Lavier, C., and G. Lambert. 1996. Dendrochronology and works of art. Pages 543-556 in J.S.
Dean, D.M. Meko, and T.W. Swetnam, eds., Tree Rings, Environment, and Humanity.
Radiocarbon 1996, University of Arizona Press, Tucson.
Orvis, K.H., and H.D. Grissino-Mayer. 2002. Standardizing the reporting of abrasive papers used
to surface tree-ring samples. Tree-Ring Research 58(1/2): 47–50.
Stokes, M.A., and T.L. Smiley. 1996. An Introduction to Tree-Ring Dating. University of
Arizona Press, Tucson. 73 pp.
Tree-Ring Dating of a Panel Painting
Page 29
Swetnam, T.W., M.A. Thompson, and E.K. Sutherland. 1985. Using dendrochronology to
measure radial growth of defoliated trees. USDA Forest Service Agricultural Handbook
639. 39 pp.
Wazny, T. 1992. Historical timber trade and its implications on dendrochronological dating. In:
T.S. Bartholin, B.E. Berglund, D. Eckstein, F.H. Schweingruber, and O. Eggertsson, eds.,
Tree Rings and Environment: Proceedings of the International Symposium, Ystad, South
Sweden, 3–9 September, 1990. Lundqua Report (Department of Quaternary Geology,
Lund University, Sweden) 34: 331–333.
Wazny, T. 2002. Baltic timber in western Europe – an exciting dendrochronological question.
Dendrochronologia 20(3): 313–320.
Tree-Ring Dating of a Panel Painting
Page 30
heartwood
sapwood
EW
LW
C
B
A
bark
one annual ring = EW + LW
Figure 1. A sequence of tree rings from a red oak (Quercus rubra L.) showing a tree ring that is
narrower (A) than a tree ring that is average in width (C), and a tree ring that is wider (B) than
average. Growth of the tree is from left to right with the center of the tree (called the “pith”)
shown by the large white dot to the left. EW = earlywood portion of ring, formed in the early
part (spring) of the growing season, and composed of large cells called “vessels” needed for
transporting water up the stem of the tree. LW = latewood portion of the ring, formed later
(summer to late summer) in the growing season, and composed of very small vessels and wood
fibers. Heartwood is non-functional (passive) wood that shows up as the darker portion of the
tree trunk, composed of wastes and toxins transported inward by ray cells. Sapwood is functional
(active) wood and consists of lighter-colored wood that serves to transport materials up the stem.
Tree-Ring Dating of a Panel Painting
Page 31
Panel rings
1.5
1.0
Reference chronology
0.51400
1450
1500
1550
1600
1650
Figure 2A. Crossdating a sequence of undated (“floating”) tree rings (top, labeled “panel rings”)
against a reference tree-ring chronology created previously for the geographic region. The
sequence of ring measurements from the panel is slid towards the left one year at a time until the
sequence falls in place, much like fingerprint matching.
Panel rings
1.5
1.0
Reference chronology
0.51400
1450
1500
1550
1600
1650
Figure 2B. The sequence of undated rings from the panel now matches the pattern from the
reference chronology below, indicating rings on the oak panel that were formed between the
years 1400 and 1540.
Tree-Ring Dating of a Panel Painting
Page 32
Figure 3. A triptych (work of art that consists of three painted panels hinged together) by Rogier
van der Weyden. The two panels on the left (The Nativity and The Pietà) are housed in the
Capilla Real, Granada, while the right panel (Christ Appearing to His Mother) is housed in the
Metropolitan Museum of Art in New York. A second identical triptych is displayed in BerlinDahlem. Art historians believed the Metropolitan-Granada triptych to be the original while the
Berlin triptych was believed to the a copy. However, the Berlin triptych has an outermost ring
dated to 1406 while tree rings from the wood of the Metropolitan triptych was cut after 1482,
almost two decades after van der Weyden’s death in 1464. Tree-ring dating techniques
demonstrated that Berlin-Dahlem instead has the early original painting from Rogier van der
Weyden’s lifetime while New York and Granada have a posthumous copy (adapted from
Kuniholm 2000).
Tree-Ring Dating of a Panel Painting
Figure 4. The painting that was analyzed at the Laboratory of Tree-Ring
Science, University of Tennessee, on 5 May 2004 and again on 23 June
2004.
Page 33
Tree-Ring Dating of a Panel Painting
Page 34
Figure 5. The painting was removed from its frame and the top and bottom of each of the three
panels were carefully and meticulously polished with fine-mesh finishing film. This polishing
was necessary to reveal the cellular structure of the wood so that rings could be easily
discerned and measured.
Tree-Ring Dating of a Panel Painting
Figure 6. The painting was next carefully secured via cushioned
clamps to a custom-designed brace that was attached to a Velmex
movable stage micrometer that rested on the floor. Shown are Dr.
Henri D. Grissino-Mayer (left) and laboratory technician Daniel
Lewis (right).
Page 35
Tree-Ring Dating of a Panel Painting
Page 36
Figure 7. The vertical alignment of the painting was crucial to ensure that ring measurements
were as precise as possible. The microscope above the painting was fitted with a SONY color
CCD camera that projected the tree rings from the panels onto a color video monitor. The three
panels can clearly be seen, connected with two sets of cross braces on the top and middle
sections of the painting. Shown are laboratory technicians Saskia van de Gevel (left), Evan
Larson (center), and Dr. Henri D. Grissino-Mayer (right).
Tree-Ring Dating of a Panel Painting
Page 37
Figure 8. A 2 X 2 contingency table set up for a chi-square analysis. “Test series” is the tree-ring
series that is being dated, while “Reference series” is the reference chronology. Rings are
evaluated as being wide or narrow for both series. If the two series are aligned correctly, then the
wide and narrow rings should match up between the two, in the shaded cells A and D.
Mismatched rings will occupy cells B and C. The “actual” number of matches or mismatches is
placed in each cell, along with the “expected” number in each cell, from which the chi-square
statistic is generated.
Tree-Ring Dating of a Panel Painting
Page 38
Figure 9-1. Tree rings found on Panel 1, shown here as the lighter bands that go up and down
relative the panel. Growth is from the left to right. The curvature of the rings on the inside
towards the left of the photograph indicates this panel was cut off-center (called a “tangential
cut,” see Figure 10). The darker bands that are almost perpendicular to the rings are ray cells that
emanate from the center of the tree. These can occasionally cause a ring to become offset when
divided by a ray cell.
Figure 9-2. Tree rings found on Panel 2, the middle panel. Growth is again from left to right.
The rings are nearly perpendicular to the core, indicating this panel was cut with the center of the
log (called “radial cut”). Notice also that the ray cells are almost parallel to the panel itself, again
indicating a position in the log that is aligned with the center. This was the highest-quality panel
of the three for tree-ring dating purposes.
Figure 9-3. Tree rings found on Panel 3. Growth is from left to right. The rings on this panel
were the most problematic, being unclear in some locations. In addition, the ray cells (the darker
bands perpendicular to the lighter-colored rings) caused significant offsets of rings on either side
of the ray, which can be clearly seen inside the red circles.
Tree-Ring Dating of a Panel Painting
Figure 10. Different cuts from a log that demonstrate the various locations
of the panels used in paintings by noting the: (1) curvature of innermost
rings, (2) presence or absence of heartwood, (3) presence or absence of bark
(which provides a precise cutting date) (from Kuniholm 2000).
Page 39
Tree-Ring Dating of a Panel Painting
Page 40
Figure 11. The skeleton plot for the tree rings from Panel 2 (top) were overlain on top of the ring
patterns from the Baltic 1 reference chronology (bottom). The match shows that the rings from
Panel 2 date from A.D. 1369 to 1585.
Tree-Ring Dating of a Panel Painting
Page 41
Standard Deviation Units
3
2
1
0
-1
-2
-3
1350
1375
1400
1425
1450
1475
1500
1525
1550
1575
1600
Figure 12A. Line graphs showing the high level of correspondence between the measurements
from Panel 2 (black line) and the tree-ring indices from the Baltic 1 reference chronology (red
line) made available from the University of Sheffield Dendrochronology Laboratory. All data
were converted to standard deviation units (z-scores) to give both series a common mean (0.0)
and standard deviation (1.0) for ease in comparison. Note especially the strong level of
correspondence in the long-term trends (low-frequency variation).
Standard Deviation Units
3
2
1
0
-1
-2
-3
1350
1375
1400
1425
1450
1475
1500
1525
1550
1575
1600
Figure 12B. Line graphs showing the high level of correspondence between the measurements
from Panel 2 (black line) and the tree-ring indices from the Netherlands Baltic chronology (red
line) made available from the Netherlands Centre for Dendrochronology.
Tree-Ring Dating of a Panel Painting
Figure 13. The final dated positions for the three panels
compared against the Baltic 1 reference chronology.
Page 42
Tree-Ring Dating of a Panel Painting
Page 43
APPENDIX 1
A Complete Listing of Published Articles that Used Tree-Ring Dating on Panel Paintings
(arranged chronologically)
Bauch, J., and D. Eckstein. 1970. Dendrochronological dating of oak panels of Dutch
seventeenth-century paintings. Studies in Conservation 15: 45–50.
Corona, E. 1970. Note dendrocronologiche sul quadro di S. Maria della Clemenza in Roma.
Studi Trentini di Scienze Naturali 47(2): 133–140.
Meier-Siem, M. 1970. Die Beurteilung von Gemälden unter Berücksichtigung der
jahrringchronologischen Datierung der Bildtafel und anderer technologischer Methoden.
Mitteilungen der Bundesforschungsanstalt für Forst und Holzwirtschaft, Reinbek bei
Hamburg 77: 59–70.
Bauch, J., D. Eckstein, and M. Maier-Siem. 1972. Dating the wood of panels by a
dendrochronological analysis of the tree-rings. Nederlands Kunsthistorisch Jaarboek 23:
485–496.
Fletcher, J.M. 1973. European dendrochronology and C-14 dating of timber. In: T. Watkins, ed.,
Radiocarbon: Calibration and Prehistory. Edinburgh University Press, Edinburgh, Scotland:
9–27.
Bauch, J., D. Eckstein, and G. Brauner. 1974. Dendrochronologische Untersuchungen an
Gemäldentafeln und Plastiken. Maltechnik Restauro 80: 32–40.
Eckstein, D., and J. Bauch. 1974. Dendrochronologie und Kunstgeschichte, dargestellt an
Gemälden holländischer und altdeutscher Malerei. Mitteilungen der deutschen
Dendrologischen Gesellschaft 67: 234–243.
Fletcher, J.M. 1974. Tree ring dates for some panel paintings in England. The Burlington
Magazine 116: 250–258.
Fletcher, J.M. 1974. Slices from a deep cake – dating panel paintings of St. Etheldreda from Ely.
Country Life 155(4004): 728–730.
Bauch, J., D. Eckstein, and G. Brauner. 1974. Dendrochronologische Untersuchungen an
Gemäldetafeln und Plastiken. Maltechnik Restauro (1/74): 32–40.
Grosser, D. 1974. Holzanatomische Untersuchungsverfahren an kunstgeschichtlichen,
kulturgeschichtlichen und archäologischen Objekten. Maltechnik Restauro 80: 68–86.
Bauch, J., and D. Eckstein. 1975. Tree-ring analysis applied to the dating of paintings. In:
Bioecological fundamentals of dendrochronology. Symposium materials of Xll-international
botanical congress, Leningrad, July, 1975. 13–15.
Tree-Ring Dating of a Panel Painting
Page 44
Grosser, D., and E. Geier. 1975. Die in der Tafelmalerei und Bildschnitzerei verwendeten
Holzarten und ihre Bestimmung nach mikroskopischen Merkmalen. Teil I. Nadelhölzer.
Maltechnik Restauro 3: 127–148.
Fletcher, J.M. 1976. A group of English royal portraits painted soon after 1513. A
dendrochronological study. Studies in Conservation 21: 171–178.
Grosser, D., and E. Graessle. 1976. Die in der Tafelmalerei und Bildschnitzerei verwendeten
Holzarten und ihre Bestimmung nach mikroskopischen Merkmalen. Teil II. Europäische
Laubhölzer, Fortsetzung. Maltechnik Restauro 4: 232–252.
Grosser, D., and E. Graessle. 1976. Die in der Tafelmalerei und Bildschnitzerei verwendeten
Holzarten und ihre Bestimmung nach mikroskopischen Merkmalen. Teil II. Europäische
Laubhölzer. Maltechnik Restauro 4: 40–54.
Fletcher, J. 1977. What wooden panels can reveal. Conservator 1: 12–16.
Fletcher, J.M. 1978. Tree-ring analysis of panel paintings and chests. In: J. Fletcher, ed.,
Dendrochronology in Europe. British Archaeological Reports International Series 51: 303–
306.
Klein, P. 1979. Alte Gemälde auf Holz gemalt. Jahrringanalytische Untersuchungen an
Gemäldetafeln. Holz Zentralblatt 105(153): 2287–2288.
Fletcher, J.M. 1980. Tree-ring dating of Tudor portraits. Proceedings of the Royal Institute of
Great Britain 52: 81–104.
Fletcher, J.M. 1980. Dendrochronology: principles for its application to oak in Northern France.
In: Actes du XX symposium international d’archéométrie, Paris 26–29 mars 1980 Volume 1.
Revue d'Archeometrie 4: 1–8.
Bauch, J., and D. Eckstein. 1981. Wood biological investigations on panels of Rembrandt
paintings. Wood Science and Technology 15: 251–263.
Klein, P. 1981. Dendrochronologische Untersuchungen an Eichenholztafeln von Rogier Van der
Weyden. Jahrbuch der Berliner Museen 23: 113–123.
Bauch, J. 1981. Dendrochronology of wood panels, demonstrated by analysis of the painting The
incredulity of Thomas. In: Rembrandt and the Incredulity of Thomas: Papers on a
Rediscovered Painting from the Seventeenth Century. Verlag Aliotta and Manhart, Leiden:
35–39.
Klein, P. 1981. Holz und Kunst. Holzanalytische Untersuchungen am Tostedter Altar. Zeitschrift
des Vereins für Geschichte, Natur- und Heimatkunde Tostedt und Umgebung 1/81: 10–15.
Tree-Ring Dating of a Panel Painting
Page 45
Fletcher, J. 1982. Panel examination and dendrochronology. The J. Getty Museum Journal 10:
39–44.
Gaborit, J.-R. 1983. L'‚tude des bois en laboratoire. Revue de l'Art 60: 70.
Klein, P. 1983. Dating of art-historical objects. In: D. Eckstein, S. Wrobel, and R.W. Aniol, eds.,
Dendrochronology and Archaeology in Europe. Mitteilungen der Bundesforschungsanstalt
für Forst- und Holzwirtschaft, Hamburg 141: 209–222.
Klein, P. 1983. L'examen dendrochronologique des panneaux peints. Revue de l'Art 60: 71–72.
Baillie, M.G.L. 1984. Some thoughts on art-historical dendrochronology. Journal of
Archaeological Science 11: 371–393.
Fletcher, J.M., and M.C. Tapper. 1984. Medieval artefacts and structures dated by
dendrochronology. Medieval Archaeology 28: 112–132.
Klein, P. 1984. Dendrochronological studies on panels by Jean Fouquet (1415/20–1477/81). In:
ICOM, Committee for Conservation, Seventh Triennial Meeting, September 1984,
Copenhagen. 25–26.
Corona, E. 1984. Il supporto ligneo della Pala di Monteluce. Bollettino dei musei e gallerie
pontificie 5: 137–151.
Baillie, M.G.L., J. Hilliam, K.R. Briffa, and D.M. Brown. 1985. Age-dating (Re-dating) the
English art-historical tree-ring chronologies. Nature 315(6017): 317–319.
Klein, P. 1985. Dendrochronologische Untersuchungen
Musikinstrumenten. Dendrochronologia 3: 25–44.
an
Gemäldetafeln
und
Bunney, S. 1985. Tree-ring dating for paintings is thrown into doubt. New Scientist (24): 37.
Klein, P. 1986. Age determinations based on dendrochronology. In: R. van Shoute and H.
Verougstraete-Marcq, eds., Scientific Examination of Easel Paintings. PACT 13: 225–237.
Klein, P. 1986. Dendrochronological analysis of early Netherlandish panels in The National
Gallery. In: Early Netherlandish Paintings. National Gallery of Art, Cambridge University
Press, Cambridge, United Kingdom: 259–260.
Klein, P. 1987. Dendrochronologische Untersuchungen an Bildtafeln des 15. Jahrhunderts. In: Le
dessin sous-jacent dans la peinture. Colloque VI, 12–14 September 1985. Universit‚ de
Louvain-la-Neuve: 29–40.
Klein, P., D. Eckstein, T. Wazny, and J. Bauch. 1987. New findings for the dendrochronological
dating of panel paintings of the 15th to 17th century. In: Scientific Examination of Works of
Art, Volume 1. International Council of Museums Working Group: 51–54.
Tree-Ring Dating of a Panel Painting
Page 46
Klein, P. 1989. Dendrochronological examinations on panel paintings and musical instruments.
Erdeszeti es Faipari Tudomanyos Kozlemenyei 0(2): 107–124.
Klein, P. 1989. Dendrochronological studies on oak panels of Rogier van der Weyden and his
circle. In: Le dessin sous-jacent dans la peinture. Colloque VII, September 1985. Universit‚
Louvain-La-Neuve: 25–36.
Klein, P. 1989. Zum Forschungsstand der Dendrochronologie europäischer Tafelmalerei.
Restauratorenblaetter 10: 35–47.
Hoffsummer, P. 1989. La dendrochronologie des panneaux peints . L'exemple d'un plafond peint
par Damery. Alden Biesen. Bulletin de l'Institut archéologique lingois 101: 33–47.
Klein, P. 1990. Tree-ring chronologies of conifer wood and its application to the dating of
panels. In: ICOM, Committee for Conservation, Ninth Triennial Meeting, August 1990,
Dresden. 38–40.
Klein, P., and J. Bauch. 1990. Analyses of wood from Italian paintings with special reference to
Raphael. In: J. Shearman and M.B. Hall, eds., The Princeton Raphael Symposium 1983.
Princeton University Press, Princeton, NJ: 85–91.
Klein, P. 1991. Dendrochronologische Untersuchungen an Gemäldetafeln der Hamburger
Kunsthalle. In: T. Sello and R. Mueller, eds., Nicht nur mit Pinsel und Oel. Verlag am
Galgenberg, Hamburg, Germany: 108–113.
Klein, P. 1991. The differentiation of originals and copies of Netherlandish panel paintings by
dendrochronology. In: Le dessin sous-jacent dans la peinture. Colloque VIII, September
1989. Universit‚ Louvain-La-Neuve: 29–42.
Klein, P., and T. Wazny. 1991. Dendrochronological analyses of paintings of Gdansk painters of
the 15th to the 17th century. Dendrochronologia 9: 181–191.
Bonde, N., T. Bartholin, K. Christensen, A. Daly, and O.H. Eriksen. 1993. Dendrokronologiske
dateringsundersogelser pa Nationalmuseet 1992. Arkeologiske udgravninger i Danmark:
305–321.
Bonde, N., T. Bartholin, K. Christensen, and O.H. Ericksen. 1993. Dendrokronologiske
dateringsundersogelser pa Nationalmuseet 1993. Arkeologiske udgravninger i Danmark:
294–310.
Klein, P. 1993. An overview about dendrochronological analyses of panel paintings. In: Le
dessin sous-jacent dans la peinture. Colloque IX, September 1991. Universit‚ de Louvain-laNeuve: 165–178.
Tree-Ring Dating of a Panel Painting
Page 47
Klein, P. 1993. Dendrochronologische Untersuchungen an Gemälden von Stefan Lochner und
Nachfolge. In: Stefan Lochner – Meister in Koeln. Ausstellungs-Katalog, Koeln, WallrafRichartz-Museum: 187–189.
Klein, P. 1993. Dendrochronologische Untersuchungen an Niederländischen Tafelbildern des 15.
und der ersten Hälfte des 16. Jahrhunderts im Städel. In: J. Sander, ed., Niederlaendische
Gemaelde im Staedel 1400–1500. Verlag Phillip von Zabern, Mainz am Rhein, Germany:
453–457.
Klein, P. 1993. Dendrochronological analysis of German panels in the National Gallery of Art.
In: J.O. Hand and S.E. Mansfield, eds., German Paintings of the Fifteenth through
Seventeenth Centuries. National Gallery of Art, Washington, D.C., Cambridge University
Press, Cambridge, United Kingdom: 195–197.
Plahter, U. 1993. Norwegian altar fronts. A medieval panel construction suitable for
dendrochronology? In: O. Storsletten and T. Thun, eds., Dendrochronology and the
Investigation of Buildings, Proceedings of an International Seminar at the Academy of
Science and Ketters, Oslo, 1–2 November, 1991. Riksantikvarens Rapporter 22: 62–70.
Klein, P. 1994. Dendrochronological analysis of panels attributed to Petrus Christus. In: Petrus
Christus, Renaissance Master of Bruges. Metropolitan Museum of Art, New York: 213–215.
Klein, P. 1994. Lucas Cranach und seine Werkstatt. Holzarten und dendrochronologische
Analyse. In: C. Grimm, J. Erichsen, and E. Brockhoff, eds., Lucas Cranach. Ein MalerUnternehmer aus Franken. Veröffenlichungen zur Bayerischen Geschichte und Kultur 26:
194–200.
Bräker, O.U. 1994. Witterungs- und Klimamodelle mit Jahrringen, eine Fallstudie mit Holz aus
Zillis, Schams. Bündner Wald 47(6): 59–67.
Corona, E. 1994. Sulla caratterizzazione dei manufatti lignei: opere pittoriche. Italia Forestale e
Montana 49(4): 401–412.
Klein, P. 1994. Dendrochronological analysis of panels of Hans Memling. In: Essays, Hans
Memling. Stedelijke Museum, Brügge: 101–103.
Klein, P. 1994. Holzartenbestimmung und dendrochronologische Analyse an Gemäldetafeln von
Lucas Cranach d.Ž. und seiner Werkstatt. In: Katalog des Schloßmuseums Gotha
„Gotteswort und Menschenbild“, Teil 1. Schloámuseum, Gotha: 210–215.
Baillie, M.G.L. 1995. A Slice Through Time: Dendrochronology and Precision Dating. B.T.
Batsford, London, 176 pp.
Hillam, J., and I. Tyers. 1995. Reliability and repeatability in dendrochronological analysis: tests
using the Fletcher archive of panel-painting data. Archaeometry 37(2): 395–405.
Tree-Ring Dating of a Panel Painting
Page 48
Pousset, D. 1996. Le Chateau de Vincennes: Etude dendrochronologique des lambris du donjon.
Mémoire de Diplome d’Etudes Approfondies en Méthodes et Techniques Nouvelles en
Sciences Humaines, Université de Franche-Comt, Faculté des Lettres et Sciences Humaines,
Besancon, France, Besancon, France. 76 pp.
Klein, P. 1996. Dendrochronologische Untersuchungen an Gem„ldetafeln der Malerfamilie tom
Ring. In: A. Lorenz, ed., Die Maler Tom Ring. Westfälisches Landesmuseum für Kunst und
Kulturgeschichte, Münster, Germany: 212–215.
Klein, P. 1996. Dendrochronolgicky pruzkum deskovych obrazu Hieronyma Bosche a jeho
nasledovniku. In: O. Kotkova, ed., Hieronymus Bosch – nasledovnik: Dvanactilety Jezi v
chramu. Obraz po zrestaurovani. Nationalgalerie, Prague: 54–59.
Klein, P. 1996. Dendrochronological findings in panels of the Campin group. In: S. Foister, S.
Nash, eds., Robert Campin. New directions in scholarship. National gallery in collaboration
with Brepols Publishers, London, Turnhout (Belgium): 77–86.
Stöckli, V. 1996. Sprechende Jahrringe. Terra Grischuna 2: 33–36.
Lavier, C., and G. Lambert. 1996. Dendrochronology and works of art. In: J.S. Dean, D.M.
Meko, and T.W. Swetnam, eds., Tree Rings, Environment, and Humanity. Radiocarbon 1996:
543–556.
Klein, P. 1997. Dendrochronological analyses of the two panels of “Saint Francis Receiving the
Stigmata”. In: Jan Van Eyck: Two Paintings of Saint Francis Receiving the Stigmata.
Antique Collectors Club, Woodbridge, United Kingdom: 47–50.
Arnold, M., and K. Richter. 1997. Holztechnologische Aspekte bei der Erhaltung der
Bilderdecke. In: Ch. Bläuer Böhm, H. Rutishauser and M.A. Nay, eds., Die romanische
Bilderdecke der Kirche St. Martin in Zillis. Grundlagen zur Konservierung und Pflege. Paul
Haupt, Berne: 227–242.
Klein, P. 1997. Dendrochronological analyses of panels of Hans Memling and his
contemporaries. In: H. Verougstraete, R. Van Schoute and M. Smeyers, eds., Memling
Studies. Uitgeverij Peeters, Leuven. Proceedings of the International Colloquium (Bruges,
10–12 November 1994): 287–295.
Klein, P. 1998. Dendrochronological analyses of panel paintings. In: K. Dardes, ed., The
Structural Conservation of Panel Paintings: Proceedings of a Symposium, J. Paul Getty
Museum. Oxford University Press, Oxford: 39–54.
Klein, P. 1998. Some aspects of the utilization of different wood species in certain European
workshops. In: A. Roy and P. Smith, eds., Painting techniques history, materials and studio
practice. The International Institute for Conservation of Historic and Artistic Works, London.
Contributions to the Dublin Congress 7–11 September 1998: 112–114.
Tree-Ring Dating of a Panel Painting
Page 49
Miles, D.H., and M.J. Worthington. 1999. List 100: Tree-ring dates from Oxford
Dendrochronology Laboratory: General list. Vernacular Architecture 30: 98–105.
Kuniholm, P.I. 2000. Dendrochronology (tree-ring dating) of panel paintings. In: W.S. Taft, Jr.,
and J.W. Mayer, eds., The Science of Paintings. Springer Verlag, New York: 206–226.
Vermet, B. 2001. Hieronymus Bosch: painter, workshop or style?. In: J. Koldeweij, P.
Vandenbroeck and B. Vermet, eds., Hieronymus Bosch: The Complete Paintings and
Drawings. NAI Publishers, Rotterdam, The Netherlands: 83–99.
Fraiture, P. 2002. Contribution of scientific methods to the understanding of the work of the 16th
century painter, Henri Bles. Dendrochronologia 20(3): 285–299.
Jansma, E., E. Hanraets, and T. Vernimmen. 2004. Tree-ring research on Dutch and Flemish art
and furniture. In: E. Jansma, A. Bräuning, H. Gärtner, and G. Schleser, eds., Tree Rings in
Archaeology, Climatology and Ecology, Volume 2. Proceedings of the Dendrosymposium
2003. Schriften des Forschungszentrum Jülich, Reihe Umwelt 44: 139–146.
Tree-Ring Dating of a Panel Painting
Page 50
APPENDIX 2A
The “Baltic 1” reference tree-ring chronology kindly supplied by the University of Sheffield
Dendrochronology Laboratory by Dr. Ian Tyers. The first three lines are header lines and contain
required metadata (species, range of years, investigators, date of chronology development).
Subsequent lines represent the actual data. After the site name “BALTI,” is the year/decade year
followed by the annual index (without decimals) and sample depth for the years in that decade. For
example, “BALTI 1160 122 1” in the fourth line shows that the year 1160 has an index of 1.22 based
on one measurement series. “BALTI 1210 124 6” in the tenth line shows that the year 1210 has an
index of 1.24 based on a sample depth of 6 panels. “9990” represents no data.
BAL
BAL
BAL
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
1 FLETCHER PANELS BALTIC AREA 1 - 64 TIMBER MEAN
2 BALTIC 1
3 MADE JH/IT 12/11/93 [HILLAM| 1995 #237]
11569990 09990 09990 09990 09990 09990 0 62
1160 122 1 82 1 82 1 52 1 92 1 92 1 72
1170 92 2 112 2 132 2 142 2 177 2 137 2 122
1180 130 2 108 3 125 3 162 3 164 3 115 3 147
1190 162 3 131 3 106 3 110 3 122 3 144 3 131
1200 159 4 129 4 96 4 132 4 137 4 130 4 125
1210 124 6 135 6 141 6 95 6 114 6 113 6 104
1220 92 6 84 6 112 6 114 6 95 6 119 6 75
1230 144 6 144 6 135 6 104 6 136 7 119 8 112
1240 136 9 117 9 138 9 142 9 134 9 138 9 182
1250 174 9 187 9 165 9 162 9 153 10 165 10 160
1260 132 12 102 12 141 13 110 13 136 13 122 14 142
1270 129 14 151 16 122 17 157 16 148 16 136 17 133
1280 125 21 130 21 117 21 140 23 132 23 144 23 136
1290 119 25 129 25 97 25 109 26 131 26 132 26 137
1300 142 28 140 28 151 29 140 30 122 30 120 30 118
1310 123 31 138 31 154 31 143 31 134 32 141 32 176
1320 140 32 146 32 131 32 126 33 107 33 135 34 130
1330 112 36 130 37 141 38 114 38 137 39 128 39 163
1340 136 40 160 40 141 40 122 40 131 40 148 40 133
1350 152 41 147 41 149 43 150 43 137 43 113 44 119
1360 141 49 125 49 157 49 166 50 151 50 140 50 155
1370 111 50 136 50 103 50 118 50 121 50 139 50 150
1380 161 52 178 52 156 53 147 56 157 56 128 56 139
1390 162 59 142 59 150 59 149 59 144 59 109 59 141
1400 157 59 128 60 155 61 116 61 133 61 127 61 156
1410 118 60 150 60 159 60 152 60 138 60 153 59 150
1420 115 58 110 57 115 57 87 57 106 57 120 57 106
1430 114 55 105 55 115 55 107 55 113 55 119 54 135
1440 132 54 154 54 142 54 160 54 136 53 160 53 128
1450 117 52 132 52 127 51 110 51 135 50 128 50 124
1460 142 50 100 50 89 50 83 50 118 50 101 50 96
1470 106 47 113 45 137 43 109 43 115 43 124 42 121
1480 121 42 136 42 133 42 113 42 113 42 112 42 142
1490 140 38 102 36 89 35 98 35 100 35 122 35 116
1500 126 29 158 29 139 28 137 28 121 28 129 28 146
1510 144 26 141 26 139 26 129 25 138 22 164 22 159
1520 103 19 139 19 148 18 130 16 126 15 139 12 143
1530 113 7 110 7 88 7 114 7 106 7 132 7 113
1540 126 6 125 6 134 6 144 5 140 5 170 5 126
1550 120 4 172 4 150 4 188 3 117 2 125 2 112
1560 107 1 92 1 92 1 92 1 102 1 82 1 77
1570 82 1 77 1 94 1 87 1 67 1 96 1 82
1580 102 1 92 1 86 1 102 1 97 1 102 1 132
1590 92 1 92 1 102 1 102 1 102 1 112 1 92
QUSP
1156 1597
1
1
2
3
4
4
6
6
9
9
11
14
18
24
26
30
32
34
39
40
46
50
51
56
59
60
58
56
54
53
50
49
42
40
32
28
22
11
7
5
1
1
1
1
1
82
52
107
164
130
122
104
124
100
167
138
121
100
128
139
98
154
127
123
153
82
162
162
128
85
146
142
87
135
139
130
116
119
148
107
144
148
144
127
130
97
82
107
87
112
1 102
1 92
2 125
3 130
4 171
4 145
6 92
6 122
9 83
9 169
12 105
14 133
19 97
24 142
27 131
31 123
32 151
36 123
39 140
41 133
47 95
50 142
51 171
58 137
59 117
60 159
57 138
56 92
54 125
52 151
49 103
49 127
42 107
40 139
32 113
27 136
21 121
10 138
7 110
5 144
1 112
1 82
1 97
1 112
19990
1 102
1 72
2 105
3 107
4 153
5 111
6 140
6 128
9 123
9 162
12 142
14 130
19 115
24 146
27 138
31 129
32 130
36 106
39 150
41 135
47 145
50 126
52 154
58 156
59 139
60 140
58 100
55 116
54 130
52 127
49 114
48 123
42 93
40 141
32 112
27 137
21 125
9 112
7 114
5 140
1 87
1 82
1 102
1 102
09990
1
1
2
3
4
5
6
6
9
9
12
14
20
25
28
31
32
36
40
41
48
50
52
58
59
60
58
55
54
52
50
47
42
40
30
26
21
8
7
5
1
1
1
1
0
Tree-Ring Dating of a Panel Painting
Page 51
APPENDIX 2B
The “Baltic 2” reference tree-ring chronology kindly supplied by the University of Sheffield
Dendrochronology Laboratory by Dr. Ian Tyers. See comments in Appendix 2A for explanation of
the Index format. More information on the Index format can be obtained from the World Data
Center for Paleoclimatology at http://www.ncdc.noaa.gov/paleo/treeinfo.html.
BAL
BAL
BAL
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
BALTI
1 FLETCHER PANELS BALTIC AREA 2 - 40 TIMBER MEAN
2 BALTIC 2
3 MADE JH/IT 8/4/94 [HILLAM| 1995 #237]
12579990 09990 09990 09990 09990 09990 09990
1260 142 1 122 1 162 1 152 1 182 1 132 1 202
1270 122 1 152 1 172 1 172 1 162 1 201 2 166
1280 176 2 154 3 151 3 141 3 161 4 184 4 166
1290 144 4 139 4 129 4 139 4 184 4 181 4 196
1300 195 5 185 5 209 5 155 5 113 5 99 5 141
1310 191 5 143 5 179 5 213 6 184 6 198 6 238
1320 174 6 193 6 206 8 181 8 142 8 172 8 144
1330 167 8 141 9 122 9 115 10 184 10 175 10 191
1340 162 10 192 10 171 10 158 11 165 12 196 12 150
1350 188 14 188 14 164 14 190 14 181 14 180 14 168
1360 178 17 115 17 171 17 200 18 165 18 177 18 181
1370 177 18 152 19 141 19 134 19 155 19 170 19 142
1380 183 19 199 20 160 21 183 21 166 21 177 21 167
1390 173 20 177 22 175 22 153 23 166 24 138 24 161
1400 191 25 177 27 176 27 130 27 145 27 167 27 216
1410 161 25 180 25 174 24 173 25 176 24 164 26 180
1420 138 25 157 24 141 24 124 24 111 24 133 24 122
1430 152 24 153 24 167 24 143 24 151 24 159 24 169
1440 186 24 153 24 158 25 170 25 165 26 190 26 171
1450 176 27 166 27 150 27 137 27 188 27 149 27 171
1460 190 26 150 27 151 27 156 27 156 28 168 29 186
1470 159 30 168 30 186 30 171 30 151 30 185 30 167
1480 215 30 240 30 211 30 192 30 210 30 180 30 257
1490 201 30 172 30 166 30 195 29 187 29 218 29 192
1500 172 29 219 29 204 28 191 28 187 28 171 28 199
1510 191 28 210 27 190 26 171 26 206 26 239 26 201
1520 165 23 175 23 178 22 216 22 194 22 154 22 202
1530 158 20 157 20 121 20 172 20 178 20 153 19 143
1540 182 18 171 18 201 18 175 18 174 18 188 18 181
1550 186 17 160 17 156 17 165 16 156 14 184 12 170
1560 194 9 202 9 209 8 215 7 175 7 200 6 175
1570 226 4 176 4 179 4 156 4 181 4 221 4 184
1580 151 2 151 1 171 1 151 1 131 1 121 1 141
1590 111 1 121 1 151 1 191 1 161 1 231 1 171
1600 111 1 101 1 131 1 111 1 111 1 101 1 81
1610 131 1 91 1 191 1 131 1 41 1 51 19990
QUSP
1257 1615
0 192
1 152
2 166
4 134
4 186
5 165
6 171
8 169
10 155
14 161
16 168
18 193
19 145
21 202
24 132
27 169
25 144
24 113
24 155
26 172
27 155
30 180
30 159
30 242
29 136
28 192
24 210
22 174
19 166
18 180
12 182
5 197
4 186
1 81
1 211
1 151
09990
1 182
1 202
2 136
4 171
4 191
5 175
6 168
8 177
10 197
14 179
16 149
18 173
19 195
21 178
24 187
26 192
25 181
25 155
24 176
26 147
26 177
30 194
30 233
30 234
29 172
28 217
23 192
22 174
18 156
18 193
12 200
5 229
4 195
1 201
1 161
1 141
09990
1 162
1 142
2 161
4 149
5 201
5 197
6 166
8 165
10 179
14 148
16 179
18 170
19 168
21 188
25 185
25 172
25 154
25 159
24 129
26 168
26 169
30 192
30 209
30 248
29 169
28 182
23 160
22 156
18 194
18 235
12 164
5 239
3 178
1 191
1 121
1 141
09990
1
1
2
4
5
5
6
8
10
14
16
18
19
20
25
25
25
25
24
26
26
30
30
30
29
28
23
22
18
18
11
5
3
1
1
1
0
Tree-Ring Dating of a Panel Painting
Page 52
APPENDIX 3A
The original measurements for Panel 2 in Decadal Format (format recognized by the
World Data Center for Paleoclimatology). Each line begins with the series ID = “panel02a”
followed by the ring number of that decade (1, 10, 20, etc.). The measurements then follow,
10 per line (except on the first and last lines). Each value is recorded in 0.01 millimeters
with the decimal removed. For example, “164” = “1.64 mm.” The “999” at the end of the
series is an end-of-series “sentinel” used by the software.
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
panel02a
1
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
164
184
121
131
122
84
81
105
130
127
123
141
112
51
122
160
148
76
146
88
95
125
198
129
191
149
123
65
104
130
82
113
115
57
115
69
152
94
132
112
84
94
107
109
190
191
131
149
87
69
122
88
115
156
68
114
129
102
97
102
83
81
92
99
111
132
130
183
145
79
95
122
103
89
121
104
88
119
92
149
122
99
99
73
94
97
95
98
109
150
156
93
130
91
94
100
111
119
110
130
88
95
100
139
110
77
94
140
108
75
108
140
164
53
100
42
96
142
135
79
100
95
79
90
101
100
104
111
96
121
122
69
117
179
178
64
92
111
116
164
103
119
114
108
61
93
149
110
134
79
95
99
134
68
132
156
147
103
92
109
99
110
134
97
85
86
128
68
138
90
97
124
81
105
137
87
132
129
172
129
118
105
162
114
129
91
124
129
90
61
123
104
102
76
93
75
133
999
171
116
93
98
100
129
153
110
96
82
124
82
92
121
115
99
77
72
104
118
Tree-Ring Dating of a Panel Painting
Page 53
APPENDIX 3B
The original measurements for Panel 1 in Decadal Format (format recognized by the
World Data Center for Paleoclimatology). Each line begins with the series ID = “panel02a”
followed by the ring number of that decade (1, 10, 20, etc.). The measurements then follow,
10 per line (except on the first and last lines). Each value is recorded in 0.01 millimeters
with the decimal removed. For example, “69” = “0.69 mm.” The “999” at the end of the
series is an end-of-series “sentinel” used by the software.
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
panel01a
1
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
69
95
55
79
91
127
85
54
59
51
94
95
86
110
104
119
65
44
69
91
56
88
98
60
48
96
101
117
70
67
65
75
122
87
107
93
99
54
46
71
52
83
61
111
96
57
112
82
72
45
49
43
90
73
89
108
56
108
42
47
76
99
71
94
62
84
66
119
87
83
56
44
45
71
119
81
49
107
95
39
61
63
55
57
73
84
58
49
127
109
64
65
43
42
117
131
47
82
105
87
65
56
111
63
89
82
65
53
24
101
122
79
75
36
62
99
109
102
100
104
72
50
65
90
76
74
76
88
44
53
83
105
68
48
32
60
124
110
92
77
119
69
58
66
76
72
98
88
75
43
45
117
123
77
53
36
89
91
93
94
106
155
76
47
60
61
85
999
80
50
66
60
87
120
67
57
34
90
91
91
59
125
92
80
45
53
71
80
78
76
88
118
117
60
62
46
95
67
74
60
108
99
82
46
63
70
52
Tree-Ring Dating of a Panel Painting
Page 54
APPENDIX 3C
The original measurements for Panel 3 in Decadal Format (format recognized by the
World Data Center for Paleoclimatology). Each line begins with the series ID = “panel02a”
followed by the ring number of that decade (1, 10, 20, etc.). The measurements then follow,
10 per line (except on the first and last lines). Each value is recorded in 0.01 millimeters
with the decimal removed. For example, “139” = “1.39 mm.” The “999” at the end of the
series is an end-of-series “sentinel” used by the software.
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
panel03a
1
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
139
120
169
165
123
167
116
88
148
114
80
108
135
179
133
123
115
236
310
100
153
144
110
89
146
179
123
88
95
129
90
65
122
152
96
146
131
247
175
71
149
201
122
129
143
141
128
109
119
148
93
86
144
147
129
144
160
127
109
89
145
134
145
90
169
127
141
121
150
133
117
74
124
138
136
136
285
116
107
90
155
153
112
112
150
108
114
110
100
121
97
112
85
154
97
93
161
91
95
112
147
107
101
132
163
117
100
124
109
133
123
92
112
156
104
101
141
85
83
122
179
131
104
138
178
109
118
140
113
127
115
90
100
140
127
141
142
128
105
130
130
139
117
134
120
117
110
146
68
136
91
134
137
179
132
145
231
105
106
131
95
142
141
108
119
118
113
119
71
131
92
139
119
133
110
98
184
180
102
999
190
154
146
130
151
87
144
113
118
119
130
130
99
148
105
164
147
100
Tree-Ring Dating of a Panel Painting
Page 55
APPENDIX 4A
COFECHA output that compares the tree rings from Panel 2 with the Baltic 1 reference chronology. The highlighted
values show the suggested date adjustment for the panel. The adjustment of “+1368” stands out and was found for 12 of
the 18 50-year segments tested. This adjustment would put the beginning year at 1+1368 = A.D. 1369. This dating
adjustment was by far the strongest of any adjustments found as shown by the “+1368 12 .44” at the bottom of the table.
The next best adjustment was to +1107, with 5 segments showing this adjustment, with an average r-value of only 0.31.
PART 8: ADJUSTMENTS FOR UNDATED SERIES:
10:10 Fri 30 Jun 2006 Page
0
-------------------------------------------------------------------------------------------------------------------------------Time span 1156 1597
442 years, best matches for
Listed in order from highest correlation
Counted
Series
Segment
-------- --------panel02a
1
50
panel02a
11
60
panel02a
21
70
panel02a
31
80
panel02a
41
90
panel02a
51 100
panel02a
61 110
panel02a
71 120
panel02a
81 130
panel02a
91 140
panel02a 101 150
panel02a 111 160
panel02a 121 170
panel02a 131 180
panel02a 141 190
panel02a 151 200
panel02a 161 210
panel02a 168 217
18 segments -
Corr
Corr
Add # 1 Add # 2
-------- -------1272 .56 1337 .48
1203 .47 1368 .46
1368 .49 1203 .46
1368 .53 1203 .42
1372 .48 1342 .46
1368 .46 1372 .46
1485 .41 1163 .35
1226 .45 1368 .39
1368 .52 1226 .45
1368 .57 1308 .36
1368 .44 1394 .37
1368 .45 1246 .39
1051 .37 1162 .33
1335 .35 1341 .34
1387 .36 1069 .36
1199 .39 1376 .38
1376 .45 1159 .44
1159 .47 1376 .42
- - - - - - -
Corr
Add # 3
-------1322 .46
1206 .45
1206 .40
1166 .38
1368 .42
1302 .43
1324 .34
1286 .33
1181 .38
1181 .36
1354 .35
1367 .37
1367 .33
1082 .33
1135 .36
1159 .36
1199 .42
1199 .37
- - -
50-year segments lagged
Corr
Corr
Add # 4 Add # 5
-------- -------1257 .43 1202 .41
1532 .42 1272 .36
1166 .36 1477 .36
1477 .37 1398 .37
1206 .41 1252 .38
1342 .40 1398 .39
1226 .33 1439 .33
1302 .33 1439 .32
1316 .37 1152 .33
1107 .35 1409 .34
1259 .33 1246 .33
1167 .34 1218 .34
1394 .32 1293 .30
1321 .30 1395 .30
1037 .36 1376 .32
1322 .35 1037 .31
1079 .36 1004 .36
1170 .33 1263 .32
- - - - - - -
Corr
Add # 6
-------1362 .38
1477 .35
1428 .34
1206 .34
1411 .36
1206 .36
1111 .33
1111 .32
1286 .33
1324 .33
1402 .32
1354 .33
1199 .29
1071 .29
1105 .31
1321 .30
1170 .33
1004 .32
- - -
10 years
Corr
Corr
Add # 7 Add # 8
-------- -------1532 .36 1243 .35
1322 .33 1158 .33
1322 .32 1411 .30
1411 .32 1372 .31
1398 .35 1477 .35
1112 .32 1411 .31
1302 .31 1389 .30
1324 .30 1152 .30
1107 .31 1439 .30
1231 .33 1226 .32
1286 .30 1231 .30
1327 .33 1381 .32
1404 .29 1107 .29
1065 .29 1417 .28
1103 .30 1071 .30
1135 .29 1221 .28
1320 .30 1235 .30
1094 .31 1089 .30
- - - - - - -
Corr
Add # 9
-------1368 .34
1428 .33
1274 .29
1504 .31
1186 .35
1252 .30
1107 .30
1397 .30
1324 .30
1286 .32
1429 .30
1152 .32
1340 .28
1155 .28
1341 .28
1187 .28
1037 .30
1063 .30
- - -
Corr
Corr
Add #10 Add #11
-------- -------1350 .33 1392 .33
1147 .32 1424 .30
1342 .28 1183 .28
1302 .30 1237 .30
1302 .33 1346 .32
1477 .29 1166 .28
1143 .30 1368 .28
1107 .30 1316 .29
1262 .30 1090 .30
1354 .31 1259 .31
1100 .30 1175 .30
1362 .31 1293 .31
1308 .28 1362 .28
1170 .28 1289 .27
1024 .27 1321 .27
1306 .27 1341 .26
1039 .29 1103 .29
1157 .29 1091 .29
- - - - - -
Number of segments
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add No R_av
+1368 12 .44 +1107 5 .31 +1206 5 .39 +1302 5 .34 +1477 5 .34 +1199 4 .37 +1226 4 .39 +1286 4 .32
+1322 4 .36 +1324 4 .32 +1376 4 .39 +1411 4 .32 +1321 3 .29 +1152 3 .32 +1170 3 .31 +1341 3 .29
+1342 3 .38 +1354 3 .33 +1362 3 .32 +1037 3 .32 +1372 3 .42 +1203 3 .45 +1398 3 .37 +1159 3 .43
Tree-Ring Dating of a Panel Painting
Page 56
APPENDIX 4B
COFECHA output that compares the tree rings from Panel 2 with the Baltic 1 reference chronology, this time testing 50year segments lagged 25 years. The highlighted values show the suggested date adjustment for the panel. The adjustment
of “+1368” stands out and was found for 5 of the 8 50-year segments tested. This adjustment would put the beginning
year at 1+1368 = A.D. 1369. This dating adjustment was the only one found for this more rigorous test.
PART 8: ADJUSTMENTS FOR UNDATED SERIES:
12:36 Fri 30 Jun 2006 Page
0
------------------------------------------------------------------------------------------------------------------------------Time span 1156 1597
442 years, best matches for
Listed in order from highest correlation
Counted
Series
Segment
-------- --------panel02a
1
50
panel02a
26
75
panel02a
51 100
panel02a
76 125
panel02a 101 150
panel02a 126 175
panel02a 151 200
panel02a 168 217
8 segments Number of segments
Add No R_av
+1368 5 .43
Corr
Corr
Add # 1 Add # 2
-------- -------1272 .56 1337 .48
1203 .45 1368 .45
1368 .46 1372 .46
1368 .47 1226 .46
1368 .44 1394 .37
1340 .42 1289 .34
1199 .39 1376 .38
1159 .47 1376 .42
- - - - - - Add No R_av
Corr
Add # 3
-------1322 .46
1206 .37
1302 .43
1286 .42
1354 .35
1341 .34
1159 .36
1199 .37
- - -
Add No R_av
50-year segments lagged
Corr
Corr
Add # 4 Add # 5
-------- -------1257 .43 1202 .41
1398 .35 1477 .34
1342 .40 1398 .39
1262 .35 1111 .35
1259 .33 1246 .33
1293 .33 1362 .32
1322 .35 1037 .31
1170 .33 1263 .32
- - - - - - Add No R_av
25 years
Corr
Add # 6
-------1362 .38
1166 .33
1206 .36
1316 .32
1402 .32
1071 .29
1321 .30
1004 .32
- - -
Add No R_av
Corr
Corr
Add # 7 Add # 8
-------- -------1532 .36 1243 .35
1130 .32 1411 .31
1112 .32 1411 .31
1152 .31 1302 .30
1286 .30 1231 .30
1051 .29 1135 .28
1135 .29 1221 .28
1094 .31 1089 .30
- - - - - - -
Add No R_av
Corr
Add # 9
-------1368 .34
1257 .31
1252 .30
1439 .30
1429 .30
1040 .28
1187 .28
1063 .30
- - -
Add No R_av
Corr
Corr
Add #10 Add #11
-------- -------1350 .33 1392 .33
1428 .31 1458 .31
1477 .29 1166 .28
1086 .29 1381 .29
1100 .30 1175 .30
1335 .27 1367 .27
1306 .27 1341 .26
1157 .29 1091 .29
- - - - - -
Add No R_av
Tree-Ring Dating of a Panel Painting
Page 57
APPENDIX 5A
COFECHA output that compares the tree rings from Panel 1 with the Baltic 1 reference chronology. The highlighted
values show the suggested date adjustment for the panel. The adjustment of “+1337” stands out and was found for 12 of
the 17 50-year segments tested. This adjustment would put the beginning year at 1+1337 = A.D. 1338. This dating
adjustment was the strongest of any adjustments found as shown by the “+1337 12 .39” at the bottom of the table. The
next best adjustment was +1396, with 7 segments showing this adjustment, with an average r-value of 0.35.
PART 8: ADJUSTMENTS FOR UNDATED SERIES:
13:52 Fri 30 Jun 2006 Page
0
-------------------------------------------------------------------------------------------------------------------------------Time span 1156 1597
442 years, best matches for
Listed in order from highest correlation
50-year segments lagged
10 years
Counted
Corr
Corr
Corr
Corr
Corr
Corr
Series
Segment
Add # 1 Add # 2 Add # 3 Add # 4 Add # 5 Add # 6
-------- --------- -------- -------- -------- -------- -------- -------panel01a
1
50 1223 .46 1337 .45 1539 .44 1289 .44 1392 .44 1272 .39
panel01a
11
60 1322 .45 1320 .41 1189 .41 1272 .40 1257 .40 1431 .34
panel01a
21
70 1226 .42 1322 .37 1323 .34 1154 .33 1335 .32 1257 .31
panel01a
31
80 1257 .41 1335 .41 1427 .39 1154 .39 1226 .37 1333 .36
panel01a
41
90 1333 .45 1335 .40 1271 .36 1472 .34 1325 .31 1173 .31
panel01a
51 100 1333 .44 1335 .41 1173 .38 1241 .36 1325 .34 1117 .31
panel01a
61 110 1169 .40 1333 .38 1220 .36 1341 .36 1335 .35 1241 .34
panel01a
71 120 1285 .40 1411 .39 1447 .37 1169 .37 1221 .36 1149 .34
panel01a
81 130 1183 .40 1334 .34 1263 .34 1408 .33 1205 .32 1169 .31
panel01a
91 140 1337 .38 1200 .38 1073 .37 1264 .35 1069 .35 1438 .34
panel01a 101 150 1337 .50 1396 .41 1060 .40 1195 .38 1390 .34 1255 .33
panel01a 111 160 1337 .46 1255 .39 1195 .36 1060 .35 1390 .35 1396 .35
panel01a 121 170 1337 .47 1195 .41 1396 .40 1329 .38 1096 .36 1350 .34
panel01a 131 180 1337 .46 1096 .41 1255 .37 1136 .35 1369 .34 1376 .33
panel01a 141 190 1255 .43 1337 .39 1096 .39 1261 .38 1195 .38 1150 .37
panel01a 151 200 1396 .36 1194 .34 1232 .32 1070 .32 1144 .32 1369 .32
panel01a 157 206 1130 .41 1194 .34 1070 .32 1144 .32 1329 .31 1369 .31
17 segments - - - - - - - - - - - - - - - - - - - - Number of segments
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add
+1337 12 .39 +1396 7 .35 +1149 5 .32 +1195 5 .37 +1255 5 .37 +1335
+1333 4 .41 +1232 3 .31 +1241 3 .33 +1154 3 .34 +1257 3 .37 +1200
+1169 3 .36 +1096 3 .39 +1362 3 .29 +1130 3 .34 +1376 3 .31 +1117
Corr
Corr
Add # 7 Add # 8
-------- -------1189 .36 1458 .33
1337 .33 1226 .33
1337 .31 1458 .30
1428 .35 1337 .33
1205 .31 1446 .31
1149 .30 1309 .30
1149 .34 1325 .33
1311 .33 1337 .32
1149 .31 1447 .31
1085 .33 1183 .33
1408 .33 1445 .32
1200 .34 1408 .33
1376 .32 1255 .31
1195 .32 1165 .32
1404 .37 1136 .35
1130 .31 1329 .29
1204 .30 1232 .30
- - - - - - -
Corr
Add # 9
-------1178 .31
1309 .32
1427 .30
1362 .32
1241 .30
1446 .30
1337 .32
1325 .32
1311 .30
1396 .32
1200 .30
1426 .31
1369 .30
1378 .32
1369 .33
1014 .27
1234 .29
- - -
Corr
Corr
Add #10 Add #11
-------- -------1396 .30 1362 .28
1392 .32 1458 .31
1497 .29 1362 .28
1393 .32 1132 .32
1432 .30 1154 .29
1426 .29 1444 .29
1411 .32 1271 .31
1117 .31 1462 .31
1341 .30 1117 .29
1454 .31 1149 .31
1084 .28 1376 .28
1137 .28 1168 .27
1130 .29 1168 .29
1159 .32 1396 .32
1296 .32 1232 .32
1099 .27 1234 .27
1058 .28 1039 .28
- - - - - -
No R_av
Add No R_av
Add No R_av
5 .38 +1369 5 .32 +1325 4 .33
3 .34 +1329 3 .33 +1226 3 .37
3 .31 +1408 3 .33 +1458 3 .31
Tree-Ring Dating of a Panel Painting
Page 58
APPENDIX 5B
COFECHA output that compares the tree rings from Panel 1 with the Baltic 1 reference chronology, this time testing 50year segments lagged 25 years. The highlighted values show the suggested date adjustment for the panel. The adjustment
of “+1337” stands out and was found for 4 of the 7 50-year segments tested. This adjustment would put the beginning
year at 1+1337 = A.D. 1338. This dating adjustment was clearly the best, ranking above the second best dating adjustment of
+1255 which had an average r-value of 0.32 for 3 segments.
PART 8: ADJUSTMENTS FOR UNDATED SERIES:
13:58 Fri 30 Jun 2006 Page
0
--------------------------------------------------------------------------------------------------------------------------------Time span 1156 1597
442 years, best matches for
Listed in order from highest correlation
50-year segments lagged
25 years
Counted
Corr
Corr
Corr
Corr
Corr
Corr
Series
Segment
Add # 1 Add # 2 Add # 3 Add # 4 Add # 5 Add # 6
-------- --------- -------- -------- -------- -------- -------- -------panel01a
1
50 1223 .46 1337 .45 1539 .44 1289 .44 1392 .44 1272 .39
panel01a
26
75 1154 .44 1226 .42 1335 .40 1257 .39 1497 .39 1427 .39
panel01a
51 100 1333 .44 1335 .41 1173 .38 1241 .36 1325 .34 1117 .31
panel01a
76 125 1447 .42 1408 .40 1183 .35 1169 .34 1273 .34 1117 .34
panel01a 101 150 1337 .50 1396 .41 1060 .40 1195 .38 1390 .34 1255 .33
panel01a 126 175 1337 .52 1096 .37 1215 .37 1195 .37 1376 .36 1116 .36
panel01a 151 200 1396 .36 1194 .34 1232 .32 1070 .32 1144 .32 1369 .32
panel01a 157 206 Lag from prior segment
6 years - insufficient
7 segments - - - - - - - - - - - - - - - - - - - - Number of segments
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add
+1337 4 .44 +1255 3 .32 +1396 3 .36
Corr
Add # 7
-------1189 .36
1333 .34
1149 .30
1311 .33
1408 .33
1350 .36
1130 .31
-
-
-
No R_av
Corr
Add # 8
-------1458 .33
1337 .31
1309 .30
1334 .33
1445 .32
1255 .33
1329 .29
-
-
-
Corr
Add # 9
-------1178 .31
1255 .30
1446 .30
1472 .32
1200 .30
1369 .32
1014 .27
-
Add No R_av
-
-
-
Corr
Add #10
-------1396 .30
1362 .29
1426 .29
1205 .32
1084 .28
1159 .30
1099 .27
-
-
Add No R_av
-
Corr
Add #11
-------1362 .28
1189 .28
1444 .29
1309 .32
1376 .28
1144 .30
1234 .27
-
-
-
Tree-Ring Dating of a Panel Painting
Page 59
APPENDIX 6A
COFECHA output that compares the tree rings from Panel 3 with the Baltic 1 reference chronology. The highlighted
values show the suggested date adjustment for the panel. No one adjustment of the top three listed stands out: (1) +1205,
7 segments, average r-value = 0.35, (2) +1223, 6 segments, average r-value = 0.40, and (3) +1392, 6 segments, average rvalue = 0.45.
PART 8: ADJUSTMENTS FOR UNDATED SERIES:
15:45 Fri 30 Jun 2006 Page
0
-------------------------------------------------------------------------------------------------------------------------------Time span 1156 1597
442 years, best matches for
Listed in order from highest correlation
50-year segments lagged
10 years
Counted
Corr
Corr
Corr
Corr
Corr
Corr
Series
Segment
Add # 1 Add # 2 Add # 3 Add # 4 Add # 5 Add # 6
-------- --------- -------- -------- -------- -------- -------- -------panel03a
1
50 1523 .46 1388 .40 1364 .38 1205 .36 1230 .34 1193 .32
panel03a
11
60 1230 .43 1205 .36 1366 .35 1372 .32 1505 .31 1425 .30
panel03a
21
70 1259 .42 1223 .38 1501 .35 1366 .33 1189 .31 1409 .29
panel03a
31
80 1259 .48 1223 .38 1207 .38 1501 .37 1366 .37 1132 .34
panel03a
41
90 1223 .46 1392 .45 1205 .39 1310 .38 1301 .38 1259 .34
panel03a
51 100 1392 .53 1223 .47 1316 .39 1205 .39 1270 .37 1310 .35
panel03a
61 110 1392 .55 1223 .42 1270 .38 1205 .37 1310 .37 1285 .33
panel03a
71 120 1392 .49 1286 .42 1310 .39 1150 .37 1270 .36 1316 .36
panel03a
81 130 1286 .41 1310 .40 1102 .40 1246 .39 1392 .35 1450 .35
panel03a
91 140 1246 .49 1102 .48 1113 .42 1233 .40 1078 .39 1154 .38
panel03a 101 150 1166 .55 1246 .42 1233 .38 1446 .38 1244 .37 1231 .36
panel03a 111 160 1166 .54 1233 .39 1350 .38 1338 .36 1231 .36 1183 .34
panel03a 121 170 1338 .42 1153 .42 1183 .38 1117 .35 1151 .34 1166 .34
panel03a 131 180 1185 .37 1183 .36 1117 .35 1305 .34 1138 .33 1119 .33
panel03a 141 190 1117 .34 1183 .33 1269 .32 1048 .32 1103 .31 1169 .30
panel03a 148 197 1103 .35 1183 .34 1319 .30 1138 .30 1169 .29 1382 .28
16 segments - - - - - - - - - - - - - - - - - - - - Number of segments
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add
+1205 7 .35 +1223 6 .40 +1392 6 .45 +1183 5 .35 +1259 5 .37 +1310
+1286 4 .35 +1316 4 .35 +1338 4 .35 +1169 3 .30 +1213 3 .31 +1117
+1113 3 .36 +1366 3 .35 +1166 3 .48 +1409 3 .31
Corr
Corr
Add # 7 Add # 8
-------- -------1418 .30 1372 .30
1200 .28 1277 .28
1205 .29 1207 .29
1392 .33 1302 .32
1316 .33 1270 .31
1157 .35 1409 .33
1362 .33 1191 .32
1222 .36 1242 .31
1154 .34 1081 .33
1181 .36 1081 .36
1113 .34 1259 .33
1308 .32 1113 .31
1119 .32 1273 .31
1216 .32 1213 .31
1338 .30 1213 .29
1079 .28 1237 .27
- - - - - - -
Corr
Add # 9
-------1499 .30
1259 .28
1286 .28
1341 .31
1115 .30
1288 .33
1316 .32
1362 .31
1078 .33
1244 .35
1338 .33
1286 .30
1269 .31
1169 .30
1189 .28
1320 .27
- - -
Corr
Corr
Add #10 Add #11
-------- -------1402 .29 1324 .27
1171 .28 1223 .28
1460 .27 1171 .27
1409 .30 1304 .30
1363 .30 1191 .29
1191 .30 1285 .30
1157 .32 1192 .31
1284 .30 1246 .29
1205 .31 1137 .30
1350 .35 1408 .34
1213 .33 1435 .32
1153 .30 1355 .30
1216 .31 1097 .30
1151 .30 1415 .29
1305 .28 1185 .28
1292 .26 1118 .25
- - - - - -
No R_av
Add No R_av
Add No R_av
5 .38 +1246 4 .40 +1270 4 .35
3 .34 +1191 3 .31 +1233 3 .39
Tree-Ring Dating of a Panel Painting
Page 60
APPENDIX 6B
COFECHA output that compares the tree rings from Panel 3 with Panel 1. The highlighted values show the suggested
date adjustment for the panel. The adjustment of “+1392” clearly stands out and was found for 11 of the 16 50-year
segments tested. This adjustment would put the beginning year at 1+1392 = A.D. 1393. This dating adjustment was the
strongest of any adjustments found as shown by the “+1392 11 .43” at the bottom of the table. The next best adjustment
was +1320, with 6 segments showing this adjustment, with an average r-value of 0.26.
PART 8: ADJUSTMENTS FOR UNDATED SERIES:
15:54 Fri 30 Jun 2006 Page
0
-------------------------------------------------------------------------------------------------------------------------------Time span 1338 1543
206 years, best matches for
Listed in order from highest correlation
50-year segments lagged
10 years
Counted
Corr
Corr
Corr
Corr
Corr
Corr
Series
Segment
Add # 1 Add # 2 Add # 3 Add # 4 Add # 5 Add # 6
-------- --------- -------- -------- -------- -------- -------- -------panel03a
1
50 1398 .45 1341 .44 1448 .35 1400 .35 1376 .33 1484 .32
panel03a
11
60 1341 .38 1376 .36 1439 .36 1368 .36 1423 .35 1392 .32
panel03a
21
70 1392 .39 1341 .34 1376 .33 1423 .33 1430 .31 1352 .31
panel03a
31
80 1392 .42 1341 .39 1375 .34 1376 .33 1439 .29 1430 .28
panel03a
41
90 1392 .55 1303 .40 1336 .35 1335 .33 1302 .28 1412 .27
panel03a
51 100 1392 .61 1301 .33 1303 .32 1319 .30 1359 .28 1302 .25
panel03a
61 110 1392 .59 1285 .39 1303 .33 1338 .28 1302 .28 1319 .27
panel03a
71 120 1392 .47 1338 .34 1359 .31 1398 .31 1322 .27 1319 .27
panel03a
81 130 1392 .47 1322 .34 1404 .33 1412 .32 1285 .31 1391 .30
panel03a
91 140 1261 .47 1322 .34 1392 .29 1250 .29 1299 .29 1346 .28
panel03a 101 150 1261 .42 1389 .30 1392 .30 1244 .29 1320 .28 1322 .28
panel03a 111 160 1231 .40 1261 .37 1320 .30 1355 .30 1265 .27 1229 .25
panel03a 121 170 1265 .44 1231 .33 1285 .32 1305 .31 1320 .30 1249 .29
panel03a 131 180 1214 .38 1265 .37 1249 .27 1231 .27 1340 .26 1216 .25
panel03a 141 190 1265 .43 1214 .39 1231 .33 1325 .32 1249 .28 1338 .27
panel03a 148 197 1255 .37 1288 .35 1214 .35 1218 .34 1325 .34 1247 .29
16 segments - - - - - - - - - - - - - - - - - - - - Number of segments
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add No R_av
Add
+1392 11 .43 +1320 6 .26 +1338 6 .26 +1391 6 .27 +1319 5 .28 +1341
+1302 4 .26 +1265 4 .38 +1231 4 .33 +1322 4 .31 +1249 4 .27 +1355
+1301 4 .26 +1439 4 .30 +1446 4 .27 +1303 3 .35 +1285 3 .34 +1214
+1423 3 .33 +1325 3 .30 +1288 3 .27
Corr
Corr
Add # 7 Add # 8
-------- -------1423 .30 1392 .29
1398 .32 1400 .32
1439 .31 1391 .30
1391 .28 1446 .28
1391 .26 1401 .26
1391 .23 1335 .22
1301 .27 1428 .26
1412 .25 1302 .23
1261 .26 1298 .25
1355 .27 1389 .25
1355 .27 1354 .26
1338 .22 1244 .21
1355 .28 1281 .27
1224 .25 1338 .24
1224 .26 1255 .25
1198 .27 1197 .27
- - - - - - -
Corr
Add # 9
-------1452 .27
1375 .30
1319 .28
1319 .26
1444 .25
1412 .21
1359 .26
1288 .23
1359 .25
1391 .24
1338 .23
1316 .21
1301 .24
1325 .24
1228 .23
1216 .26
- - -
Corr
Corr
Add #10 Add #11
-------- -------1446 .26 1439 .25
1446 .28 1425 .28
1467 .28 1446 .26
1352 .25 1409 .24
1362 .24 1353 .22
1320 .21 1336 .21
1412 .24 1342 .23
1301 .22 1368 .22
1345 .24 1320 .24
1354 .24 1320 .22
1305 .23 1359 .22
1298 .21 1354 .20
1248 .22 1361 .22
1361 .24 1284 .22
1341 .22 1288 .22
1249 .24 1345 .24
- - - - - -
No R_av
Add No R_av
Add No R_av
5 .36 +1359 5 .26 +1412 5 .26
4 .28 +1376 4 .34 +1261 4 .38
3 .37 +1398 3 .36 +1354 3 .23