Science
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Photo: Rijksmuseum (1954-43)
Renaissance bronzes (from the fifteenth
and sixteenth centuries) are an important
collection within the Rijksmuseum. Until
recently, art historians only ever studied the
style features. Exactly how the sculptures
were made was of little importance to them
however, partly because this was barely
visible.
Now, new techniques based on neutron
tomography reveal every detail of the hidden
inside. Not only does this enable one to learn
more about the artist, it also facilitates the
distinction between an original and a copy.
That could be a matter of millions.
Robert van Langh (44) is no average PhD
candidate. He considers himself a late
developer. Upon leaving secondary school he
went to a retail school in Breda, after which
he trained as a goldsmith in Antwerp. He
learned to restore fine art at the Antwerp
Institute for Fine Arts. His interest in the
scientific aspects of the various works of art
led him to research institutes in New York
and Florence. In 2006 head of conservation
& restoration Van Langh, encouraged by art
“The sculpture was initially considered a full-length portrait of William of Orange and attributed to sculptor
Hendrick de Keyser (who also sculpted his memorial stone in Delft). The walking pose and strange posture
later suggested a walking musician (a player of the violone, an early form of viola da gamba and cello). The
X-radiograph revealed a strange ‘hatch’ (a flap with a rounded top) in the back of the sculpture, for which
there was no apparent explanation.
With the aid of neutron radiography and tomography it could be established that the arms and lower legs
had been cast on separately (and not cast in one run). This led us to believe that the sculpture was originally
intended to be a moveable man, like a clockwork doll or an automaton (wind-up toy). This also explains the
walking position. In this case the ‘hatch’ on the back would have been an opening for the winding handle to
start the walking mechanism. These sculptures were especially made in Southern Germany in the sixteenth
and seventeenth centuries.
The conclusion, therefore, was that the sculpture had originally been intended as an automaton but
that it was later decided to fixate it as a standing figure and to seal the hatch in its back. Consequently,
the sculpture is no longer attributed to De Keyser but is now listed as an automaton figure of a walking
nobleman, made in Southern Germany (Neurenberg or Augsburg), c. 1580-1600. This case illustrates
beautifully how collaboration between art historians and scientists can lead to new insights.” (Frits Scholten)
historian and Rijksmuseum curator Prof.
Frits Scholten, began his doctoral research
with Prof. Joris van Dik’s research group at
the Faculty of Mechanical, Maritime and
Materials Engineering.
Van Langh’s point of departure for any
research is often a hunch that something
about a sculpture is not quite right. This was
also the case with the 35 centimetre sculpture
of the Greek demigod Hercules, attributed
to the sixteenth century sculptor Willem
later, the 3D dataset was complete.
“Wow, look at that!” Van Langh calls out
as, on his monitor, he navigates through
the inside of the sculpture up towards the
Hercules’ head. Nothing remains hidden
here. It is decidedly strange that no iron core
pins are visible on the inside of the Hercules
sculpture, but that core material can be seen
in the arms and legs. The absence of core pins
means that the sculpture is not a direct cast
but a copy.
‘Neutrons are sensitive to hydrogenous materials
such as resin and wax’
van Tetrode. X-rays had been made of the
sculpture before, but they had not shown
sufficient contrast due to the thickness of the
material.
So Hercules went to the Neutra facility at
the Paul Scherrer Institute in Switzerland.
The neutron beam used here comes from
a spallation setup: a lead plate that is
bombarded with protons delivering 600
MeV of power. The resulting neutron beam
is first slowed down and then conducted to
‘the object’. As there is very little interaction
between the neutrons and the material, the
penetrating capacity is higher than that
of X-rays. In addition, neutrons are
sensitive to hydrogenous materials,
such as resin and wax, thus also
revealing information about
soft materials. To make it even
better, the neutron images from
Switzerland are tomographic: the
sculpture was rotated 1 degree
before each following image.
Three hours and 180 degrees
Photo: Sam
Rentmeester
Neutron beams are much more suitable than X-rays for scanning bronze statues.
Good news for our art collections?
Jos Wassink
Photo: Rijksmuseum (16083)
Hercules’
head
Strange man
Something else is strange about this sculpture:
the torso is hollow but the arms and legs have
core material. As if someone had scraped
out the top of the sculpture. But how is
that possible if the sculpture is closed? The
X-rays had revealed cracks in the hair. Did
this suggest that the crown had been cast on
separately?
Close examination of the neutron images
revealed a thick lump of bronze behind the
nose. Van Langh thinks the inner mould was
damaged during the casting process. Pieces
of the inner mould material consequently
fell into the gap, blocking the flow
of bronze to the head area, which
resulted in a sculpture without
a crown. The makers then filled
the head (as the neutron images
clearly show) and made a new mould
for the missing part. A good piece of
craftsmanship, as nothing can be seen
on the outside.
‘Neutron tomography is a powerful
technique because it provides
Robert van Langh: “Neutron tomography is a
powerful technique.”
genuine ‘insight’ into these objects,’ Van
Langh writes. He believes that when studying
works of art one should also note how they
were made - something which is not done
often enough. Van Langh would love to put
the entire oeuvre of a well-known sculptor
through the neutron scanner. That could
reveal more about a person’s typical way of
working and how it develops. It could also
result in the sculpture being attributed to
someone other than would otherwise be the
case on the basis of style features alone.
‘We should look at these works differently,’ the
PhD candidate says in summary. Although he
also knows that in saying that, he will kindle
the wrath of the more conservative curators.
Robert van Langh: ‘Technical Studies of
Renaissance Bronzes’, PhD supervisors:
Prof. Joris Dik (TU) and Prof. Frits
Scholten (UvA).
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