Appendix
Sample Case study
“The mosaic at the house of Neptune and Amphitrite”
The house of Neptune and Amphitrite at Herculaneum
Eleonora Del Federico1, Cindie Kehlet1, Barbara Charton1, Hiba Schahbaz1, Agnes Haber2 and Bernhard
Blümich2
1
2
Department of Mathematics and Science, Pratt Institue, Brooklyn, NY, USA
Department of Macromolecular Chemistry, RWTH Aachen University, Aachen, Germany
Part 1
Herculaneum, Italy, 69 AD—1pm
It was late in the morning and Lavinia was coming back from shopping for the day. She had bought bread, oil,
vegetables and meat for the dinner she was going to cook for her family. It was good, she thought, to have water
in the house and not have to go fetch it from the fountain in the next corner like many other people in town. As
she was getting the pots ready to cook, she gazed through the atrium into the back room, where the workers
were getting ready to lay up the mosaic. One of them was mixing a white powder with water, while the others
were laying down beautiful little tiles on the floor. She couldn’t believe how long it has taken to restore the
room. The earthquake of 62 AD had been devastating and many areas in the city had been destroyed. It had
taken time to restore the damaged rooms of the house, and slowly, the dining room was coming back to life,
emerging like a beautiful garden. Members of the household and their guests would now be able to enjoy the
beautifully painted garden scenes as well as the colorful and expensive mosaic as they dined. This would reflect
the family’s social standing, after all, the house did not have a garden and as they belonged to the middle class,
it was essential to have a special room reserved to entertain important guests. The more she looked at the room,
the more enchanted she became. In a daze, she walked through the atrium and looked across the opening in the
back that simulated a window. It would definitely look like a beautiful garden when it is finished, with its
mosaics, paintings, fountains and a temple for the nymphs to bring good luck. The workers were ready to set the
mosaic on the wall. They had mixed sand with the white mushy substance that they had prepared earlier on
which was a mixture of water and fine white powder that had been collected the same morning, from a nearby
kiln. Lavinia knew that somehow, this white powder held secrets to how materials glued together. She
continued to observe the workers with wonder. Some were applying the mixture on to the wall and one was
working on the floor, laying small colored pieces of glass and sea shells, following up the design that her father
had commissioned from an ancient Greek painting. He had told her that the image depicted Neptune and
Amphitrite, the gods of the sea. Lavinia had heard that Amphitrite was a nymph who used to spend most of the
time singing and dancing with her sisters. One day Neptune saw her and fell in love with her. He kidnapped her
and made her his wife. What a great story for this room and for the house guests to chat about while they dine,
thought Lavinia.
Slowly the workers began to set up the pebbles one by on the wall. One of them had sketched the design in wet
mortar with a small piece of wood to avoid mistakes. Somehow, each of these individual pebbles would be
‘glued’ to the wall. She wondered what magic force would keep them together when the mortar hardened.
Lavinia’s curiosity took over and she forgot all about the dinner she had been preparing in the kitchen. She had
always been enchanted by colorful things and those little pieces of colored glass looked to her like precious
stones. Bright blue, green, red, yellow, orange, turquoise...so many different colors! She had not seen anything
like this before and found each of these little colored stones very unique and special. A workers had told her
previously that many of them had been recycled from broken bottles and vessels but she knew that the pure red,
turquoise, green and opaque yellow stones must have been especially made to use in ‘her’ mosaic. She
wondered what made some of them transparent, and others opaque and what created the many different colors.
Suddenly, the pungent smell of burning fish sauce wafted from the kitchen. Something must be burning, she
thought, and left the refuge of her favorite room to check on the night’s meal.
.
Figure 1. Left. Atrium of the house of Neptune and Amphitrite overlooking at the triclinium (room with the mosaic). Right. Triclinium
showing mosaic and Nympheum. Bottom. The mosaic of Neptune and Amphitrite at Herculaneum- Present condition
Questions
1) What are the raw materials used to prepare a mosaic?
2) Describe the chemical reactions involved in the preparation of the mortar.
3) Give the chemical reaction the mortar undergoes once it sets in contact with air?
4) What are the colored tiles (tesserae) made of?
5) What is the structure of glass at a molecular level?
8) What makes glass colored?
Useful sources
a. Historical Mosaics
http://www.getty.edu/conservation/publications/pdf_publications/mos_tech_training_ar.pdf
b. “Glass and Ceramics” from Chemistry and Artists' Colors by Mary Virginia Orna (Author) and
Madeline P. Goodstein
Part 2
August 24, 79 AD, 1:00 pm
Lavinia had just finished the preparation of the meal for her guest who were arriving that night. While it was
cooking on the stove, she checked the family’s “Fast-food” store in the next room. People were going about
their business, having a snack or two and some wine…everything was were going well and she had some time
for herself. Instead of going to the bath today, as her usual routine dictated, she decided to sneak into the garden
room and pray. The beauty of the room was overwhelming. The painted birds and flowers looked so real that
she could imagine herself in the most beautiful of gardens.
Suddenly the floor began to vibrate violently, the walls started trembling and a noise exploded in her ears. Her
brother who was tending to the snack store next door rushed in. “The gods are angry.” he said. “The big
mountain has exploded, and there is a black cloud coming this way. Let’s go towards the beach, it will be safer
there, until this passes.” Lavinia looked at her room one last time and found she was at peace. She followed her
brother and many other people trying to escape from the volcanic eruption towards the shore.
Someday in the mid 1930’s
Amadeo Mauri, the director of the excavations of Pompeii and Herculaneum had been digging the site for about
10 years. Removing twenty meters of cemented lava which covered only a few blocks of the city had been a
huge challenge. He knew that it would be almost impossible to excavate it all, in part, because now the modern
city of Ercolano was laid on top of ancient Herculaneum. Today, however, had been a especially rewarding day.
He had come across an amazing mosaic with the scene of Neptune and Amphitrite. It was made of sparkling
bright colored tesserae and appeared to be in perfect condition although it was almost two thousand years old.
There were also two wall paintings fragments, with garden scenes depicting birds and fountains and flowers on
either side of the mosaic. These too were in perfect condition, as if they were painted only yesterday.
The walls were slowly restored with modern stones simulating those used by the Romans, but with irregular
shapes so that the modern restorations could be distinguished from the old mosaic. Portland cement was use to
set the mosaic and wall paintings back in place. The foundations of the house were still intact, as was the snack
bar with amphorae still containing residues of wine, food, and olive oil. To Mauri’s astonishment, part of the
second floor with a bed and stove was also undamaged. Following the routine preservation measure, Mauri’s
workers applied several layers of a mixture of beeswax and paraffin to the wall paintings and the mosaic to
make sure that no moisture would penetrate them.
Activities
1. Visit the virtual map of Herculaneum (a) and describe the present condition of the house of Neptune
and Amphitrite (G in the map)
2. Compare the composition of ancient cement with the composition of Portland cement.
3. Was the use of Portland cement a good choice to repair the mosaic?
4. Was the coating with beeswax and paraffin a good choice as a preservation measure, for wall surfaces?
5. Propose a conservation method to set up the mosaic back in place and “glue back” the detached tesserae,
include the specific materials and materials and the techniques you would use.
Useful resources
a. http://www.proximaveritati.auckland.ac.nz/Herculaneum/
b. http://www.getty.edu/conservation/publications/pdf_publications/mos_tech_training_ar.pdf
c. http://www.getty.edu/conservation/publications/pdf_publications/orpheus_mosaic.pdf
Part 3
Summer 2009
Ellen and her students Cyndi and Megan were coming down the hill from the Circunvesuviana station towards
Ancient Herculaneum. They were carrying their portable X-Ray, Fourier Transformed Infra Red (FTIR) and
Nuclear Magnetic Resonance (NMR) instrumentation to study the mosaic of Neptune and Amphitrite. They
walked all the way down the slope towards the offices, where Giulia, the research coordinator of the site, was
waiting for them.
After introductions and coffee and some Neapolitan pastries, Ellen asked “I was wondering, Guilia, if you could
explain a little more about the condition of the mosaic and what type of information you would expect from our
the XRF, FTIR and NMR measurements?”
Giulia responded “As you know the main problem we are having at the moment are flooding and water
infiltration, which brings fungi and salt effloresces. These combined, are making the tesserae come off the
mortar.”
“That is a serious problem!” exclaimed Ellen.
Giulia continued with her explanation “The mosaic and the room in general are in a state of emergency and it is
important that we learn as much about the materials present as quickly as possible because we would like to
save this mosaic from further damage. It has been preserved in this room for nearly 2000 years and we would
like to keep it here.”
“Do you mean that you are considering the possibility of removing the mosaic from the site?” asked Cyndi.
“Well,” replied Guilia “if after our assessment we decide that it is not possible to slow down the degradation
process, it may be the wisest choice to substitute the mosaic with a copy and detach the original to preserve it
indoors. This has been done with some of the mosaics here at Herculaneum and also at Pompeii”.
“That would be unfortunate!” exclaimed Megan, “I feel that it would be sacrilegious to remove it, even if it is
replaced with a copy. It has a history and is a part of this ancient site. It is clear that the owner of the house went
to great expense to have such a mosaic and nympheum placed in this room. It belongs here and to the people
who lived here and admired it. Of course, we would like it to be admired for 2000 more years so perhaps
science, archeology, art history and conservation can work together to decide upon the best strategy to preserve
it. Is it appropriate to detach it and set it up on a museum wall? That would detract from the context and the
history of the mosaic.” she said.
“That’s right and this is why we would like to keep it here if possible.” affirmed Giulia. “So this is why we need
your help.”
Class activity:
Describe the general state of the mosaic of Neptune and Amphitrite based on the conversation above.
Discussion question
Should the mosaic be removed even though it may be endangered? Explain your reasoning.
Part 4
“So now it is your turn Ellen. Could you describe in a little more detail what XRF, FTIR and NMR can do for
us?” Giulia asked.
“XRF, will allow us to identify each of the elements with an atomic number larger than Aluminum. This would
provide information on what colorants were used to make the different colors in the glass tesserae.” said Ellen.
“Some mosaics, especially floor mosaics, are made out of stone tesserae.
Would you be able to distinguish stone from glass?” asked Giulia.
“Well,” said Ellen, “there may be some signatures depending on the material. For example, a lack of lead and
the presence of rare earths such as Zirconium, may mean that the material is natural and not glass or ceramic.”
“That’s interesting,” said Giulia, and proceeded to ask “so then XRF only provides clues and not the complete
information on the materials, right?”
“Well,” answered Ellen “XRF is an example of what we call ‘atomic spectroscopy’. It can tell us what type of
atoms are present but not how these atoms are bonded to each other and therefore one can only make ‘educated
guesses’. In order to confirm the results, one would need to resort to molecular or diffraction techniques such as
Raman Spectroscopy or X-Ray diffraction (XRD), but most of the time, XRF provides enough information and
requires no sampling.”
“FTIR will tell us whether or not there is organic material present on the surface of the mosaic or wall
painting.” said Cyndi. “If used in the ‘reflectance mode’ one does not even need to touch the wall painting to
make the studies, and although the data may be more difficult to interpret than the routine FTIR studies, the fact
that it is non-destructive and requires no sampling and not-contact with the wall, makes it worthwhile.”
“That would be great to know, since there are no records on whether there was an earlier restoration of the
mosaic when it was first unearthed. We think it was treated with beeswax as were many other surfaces during
Mauri’s excavations, but we don’t know for sure.” said Giulia.
Cyndi, who was working on her theses on NMR applied to art interjected “NMR can tell us about the moisture
distribution on the mosaic, and whether or not there is a difference among the moisture of the mosaic surface
and mortar underneath, or even in different areas of the surface of the mosaic. So for example, if there is water
absorbed within the pores of the mortar, and the pores are large, then the water is more mobile. Also there will
be a large moisture content in that area, since larger pores allow the absorption of more water. On the other
hand, if the pores are smaller, there will be less water trapped in those pores and those water molecules will
have less space to move. We will learn about the moisture content of the wall as well as the intensity of the
signal we detect. This will give us an idea about the relative amount of water in different areas of the mosaic. It
will also tell us something about its stratigraphy.”
“Can you explain that a little bit more?” asked Giulia.
“Of course.” said Ellen, and she proceeded “If there are several mortar layers below the mosaic which have
slightly different composition or porosity, it will be possible to detect differences in their water content and the
mobility of the water molecules trapped within each mortar. Unilateral NMR will be able to distinguish and
discriminate among layers and their humidity content all the way up to 2.5 cm into the wall.”
“Could you measure this at different areas on the mosaic and tell us whether the humidity content is different
above and also below the surface?” asked Giulia “If the humidity is different in different areas of the mosaic,
we are in trouble.” He added. “It seems that you can already detect that the bottom part of the mosaic is more
humid than the top, because of location of salt efflorescence.”
“Definitely.” answered Ellen, “We can make a humidity map to confirm it. We can also examine the mortar
underneath the tesserae to check for humidity.”
Study questions
1) What are the advantages and disadvantages of an in-situ non-destructive approach to this study?
2) What are the differences between IR and X-Ray and NMR radiations?
3) What type of information can you get from the following techniques
a. XRF
b.
FTIR
c. Unilateral NMR
d. XRD
e. Raman
4) What are the limitations of XRF and Unilateral NMR ?
Useful Resources

“The incredible shirking scanner” Bernhard Blümich, Scientific American, November 2008 issue.


“Saving Art in situ”, Giacomo Chiari, Nature 453, 159, 2008 doi:10.1038/453159a
“In Situ Noninvasive Study of Artworks: The MOLAB Multi-technique Approach” Costanza Miliani,
Francesca Rosi, Brunetto Giovanni Brunetti and Antonio Sgamellotti Acc. Chem. Res., 2010, 43 (6), pp
728–738

“Raman microscopy in archaeological science” Gregory D. Smith, Robin J.H. Clark, Journal of
Archaeological Science 31 (2004) 1137–1160

“The characterization of artifacts of cultural heritage significance using physical techniques” D.C.
Creagh , Radiation Physics and Chemistry 74 (2005) 426–442

The science of The Science of Paintings, Richard Newman, W. Stanley Taft, 2000

Organic Chemistry of Museum Objects, Second Edition, John Mills, Raymond White, 1999.
Part 5
After they had finished conversing, the team walked towards the house of Neptune and Amphitrite, slowly
transporting the ‘somewhat’ portable instruments through the ancient cobblestone streets and sidewalks.
“It is like going back in time!” exclaimed Ellen. “Walking on this sidewalk, I feel like an ancient citizen on the
street.” she added.
After maneuvering through the archaic sidewalks, the team arrived to their destination. “This must have been a
wonderful room.” said Ellen. “If you look hard enough you can see that there are garden scenes painted here,
with birds and water fountains.”
“Right now you can barely see them due to the salt damage, but they were brightly colored at the time of
excavation, 70 years ago.” Giulia said.
In the meantime, Megan and Cyndi were taking notes choosing the different areas to measure by XRF. They
noticed many different colors and one interesting feature. Many of the red tesserae had turned green on the
surface.
“That’s odd,” said Megan “let’s see what information the XRF spectrum can provide us.”
After some hours measuring different sites of the mosaic, Cyndi and Megan were ready to report their
preliminary XRF results.
“We have found that all tesserae, regardless of their color and look contain the following elements: Silicon,
Calcium, Iron and Lead, and that the presence and intensity for Copper, Cobalt, Manganese and Antimony vary
with their color. For example we have found out that Cobalt is only present in deep blue tesserae but that both
green and red tesserae contain Copper. At the same time we see that high content of antimony is associated with
the yellow tesserae.”
“We also found that as the blues become paler, there is an increase in the intensity of the antimony peak, as if it
would have been used to lighten the colors.” said Megan.
“Can you tell whether some of the tesserae are not made of glass?” asked Giulia.
“Well, it is known that Roman glass contains high amounts of lead, so lack of lead and the presence of rare
elements like Barium or Zirconium suggest minerals. The brown tesserae presents mostly a large peak for
Calcium and and a medium peak for Iron. This is indicative of marble or limestone possibly being used here.
We would, however, need to use XRD to confirm that.”
“I understand.” said Giulia.
Some hours later, Ellen reported on the infra red measurements. “I can definitely assure you that there is an
organic coating both on the wall painting and on the mosaic, which looks almost the same. This suggests that
the same material was used for the consolidation of both, possibly at the same time, since I can almost overlay
the spectra. Furthermore, I can see peaks at 1740 cm-1, and between 2800-3000 cm-1 which clearly indicates the
presence of a lipidic substance.”
“That is good information.” interjected Giulia. “Now we know that there is an organic coating which may be
preventing the moisture of the wall to reach equilibrium with its environment. This would cause the pressure at
the interface between the paint layer and the coating to eventually crack the surface with the end result being
either the detachment of the paint layer or that of the tesserae. It is time now to discuss with the conservators
what the next steps will be to preserve the mosaic.”
Questions
1) How did the scientists figure out that Mauri’s worker had indeed applied a layer of beeswax to the
mosaic and the wall paintings?
2) Looking at the XRF data presented in the case study, decide what elemental composition is associated
with the following tessera colors
a. Red
b. Green
c. Yellow
d. Deep Blue
e. Pale Blue
3) Suggest a mechanism by which a red colored tesseara changes to green color upon degradation
4) Looking at the NMR data in the next page, explain whether or not the moisture distribution of the
mosaic is uniform
Sources
1.
The Herculaneum Conservation Project
a. http://www.bsr.ac.uk/wp-content/uploads/plugin-CMAS_introduction_Wallace-Hadrill.pdf
b. http://www.bsr.ac.uk/research/archaeology/ongoing-projects/herculaneum/herculaneumconservation-project

“Ancient glass deterioration in mosaics of Pompeii.” Surface Engineering 2005, 21.5-6 pages 402-405

“Archaeometric investigation of Roman tesserae from Herculaneum (Italy) by the combined use of
complementary micro-destructive analytical techniques” I. van der Werf, A. Mangone, L. C. Giannossa,
A. Traini. R. Laviano, A. Coralini, L. Sabbatini. Journal of Archaeological Science 36 (2009) 2625–
2634.

“Ancient Roman wall paintings mapped nondestructively by portable NMR” A. Haber, B. Blümich, D.
Souvorova, E. Del Federico. Submitted to Analytical and Bioanalytical Chemistry

“ Non-invasive deph profiling of walls by portable Nuclear Magnetic Resonance” B. Blümich, A. Haber,
F. Casanova, E. Del Federico, V. Boardman, G. Wahl, A. Stilliano, L. Isolani. Anal Bioanal Chem. 2010
397(7):3117-25.