[Answer for this question is the same as for The 1532 fire and image properties]
Although the fire of 1532 nearly destroyed the Shroud, it created opportunities for many types of chemical studies. We would never use the same destructive methods of observation on an undamaged relic, but misadventure gave us many unexpected options. The important fact is that, before the restoration, we could look at the chemistry of specific locations on the Shroud where scorches intersected image, blood, serum, and water stains. The restoration destroyed much chemical information at those intersections.
If the image had been painted or retouched, some foreign materials had to be added to the cloth. The pigments and vehicles (e.g., the ochers, realgar, orpiment, mosaic gold, glair, gums, and glues) would have been subjected to a violent "chemical test" during the fire. The temperatures, temperature gradients, pyrolysis products, and water used to extinguish the fire would have changed the chemical composition of most foreign materials. Before going to Turin in 1978, we did many experiments on the stability of the painting materials. We had hoped that future observations on the Shroud could compare predictions with reality. The restoration disturbed exactly the areas of most chemical importance.
The persons involved in the restoration of June and July 2002 did not appear to be familiar with previous scientific observations, and they did not consult chemists with different areas of experience or chemically-oriented textile conservators. The restoration destroyed much of the chemical information that could have been recovered as a function of position on the surface of the Shroud.
The fire of 1532 produced many extremely reactive pyrolysis products, and the fire was extinguished with water. All paints that were used during or before medieval times (except gold) are changed by heat and/or the chemically reducing and reactive pyrolysis products of the cloth (e.g., formaldehyde, furfural, organic acids, CO, etc.). For example, red hematite would have been reduced to black magnetite. This fact provided one basis for refuting McCrone’s claim that the image was painted with hematite. We planned to look for the products of such reactions. Some medieval painting materials become water soluble, and they would have moved with the water. A huge amount of chemical information existed in the scorches.
Most organic colors are much less stable than cellulose (linen) and the normal inorganic pigments. Experiments in 1978 showed that scorch lines in impurities precede the scorches in pure linen. Most organic materials, including natural products, change in predictable ways in response to heating and the known products of cellulose pyrolysis. We even tested squid ink, which had been reported being used in ancient times.
It might still be possible to extract the products of the reactions from the materials recovered during the restoration, assuming that samples were segregated and locations were recorded. Such information could be important for suggesting the chemical composition of the image. Most possibilities for directly studying the effects of the fire on image materials were destroyed by the restoration of 2002.
Visual and microscopic observations on the Shroud in 1978 indicated that image color or its reaction products did not move with the water. Other unidentified products did move. Aldo Guerreschi has suggested that two different sets of water stains exist on the Shroud. They could contain interesting chemical and historical information. We had counted on the tape samples and possible future direct studies on the scorch/water-stain areas of the Shroud for detailed chemical confirmation of what did and did not move with the water. Now the tape samples are kept from scientific study by the officials in Turin, and scorches were destroyed by the "restoration."
The Shroud showed many locations where scorches of different severity intersected image and/or blood. Thermal gradients can be estimated on the basis of scorch colors. Temperatures are the most important factors in calculating chemical rates. We made predictions on the kinds of products that might appear in image areas as a result of reactions between its components and the pyrolysis products and water. These predictions could be used to test many of the hypotheses that have been proposed for image formation.
I took samples from many scorch/water/image intersections in 1978, but observations on them generated more questions. Answers required additional observations and/or samples. The samples are now secreted in Turin. As a result of the restoration, any future studies will be much more difficult and expensive: Some will be impossible.
The Shroud is a structure composed of chemical compounds, and all of the main ones have been studied in detail. They are published in chemical text books. Chemical analyses can yield considerable definitive historical information. All manipulations of the Shroud should be considered in detail in order to preserve as much information as possible.
Linen-production technology has changed through the centuries. We have assembled chemical information related to the technology, and we have consulted textile experts who have done detailed chemical research that relates to the composition of the Shroud. Our detailed analyses suggested that the cloth had been prepared by technology common before about AD 1200. It best resembles linen made in the Near East during Roman times. These results do not agree with the date published in 1989. The differences can be explained on the basis of samples from the radiocarbon area, but all scientific observations should be confirmed. Samples from the restoration might help confirm the properties of the radiocarbon sample; however, the persons involved in the restoration fight any attempt to test and confirm the truth. No scientist in Torino will discuss the problem, and the custodians refuse to recognize the problem. Ethical science is impossible in such an environment.
Lignin is a structural polymer that is found in all plants, including flax. Linen is bleached in an effort to remove as much lignin as possible, but some lignin always remains in linen. Lignin slowly ages with the loss of vanillin (4-hydroxy-2-methoxybenzaldehyde). A very sensitive microchemical test exists for the detection of traces of vanillin. It is easy to detect vanillin in modern lignin, it is harder to find in Medieval linen, and no test can be obtained from the few Shroud fibers that are still available for study. The lignin in samples from the Dead Sea scrolls (ca. AD 70) does not give the vanillin test. This observation would suggest that the linen of the Shroud is very old, casting doubt on the accuracy of the 1988 date. Observations on the lignin could be confirmed with samples from the "restoration"; however, such samples are jealously guarded in Turin.
The tape samples show that much of the charred material is elemental carbon. It is very inert chemically. It would not have changed during the 470 years since the fire. Published concerns about isotope fractionation during the fire are nonsense. The carbonized material can easily be chemically cleaned of any organic deposits that might have appeared after the fire, making it an ideal material for radiocarbon dating. Before the restoration, the carbon from specific areas could have been dated separately, giving critical information about the homogeneity of the cloth as well as "clusters" of dates. Clusters of dates are more reliable than dates on single samples.
Dr. Max Frei took tape samples to recover pollen grains from the surface of the Shroud in 1973 and 1978. Sweeping claims have been made on the basis of Frei’s samples, but published photomicrographs do not support the claims. Other reports suggest that there were major changes in the number of grains found on Frei’s tapes between the time of his death and more recent publications. The pollen data badly need confirmation. The restoration totally destroyed any chance to take valid additional pollen-grain samples from the surface of the Shroud. A suspicious person might wonder whether the "restoration" was rushed through to prevent ethical work on confirming both chemical and pollen observations.
Biblical accounts suggested several types of compounds that might have appeared on the cloth (e.g., aloes, myrrh, sebaceous secretions, etc.). We planned and executed chemical analytical methods that could detect them in 1978. Those methods were extremely sensitive, but they did not detect squalene or myrrh. These results could have been confirmed by additional tests on the Shroud, but the "restoration" has totally changed the Shroud’s surface.
The surface of the Shroud could have been analyzed by Electron Spectroscopy for Chemical Analysis (ESCA), which observes the top few nanometers of the surface. Now that the surface has been disturbed, that powerful technique will be much more difficult to apply, and results will be ambiguous. This is a terrible, discouraging loss for Shroud chemists.
The problems associated with surface analyses are now compounded by the fact that thymol was used to sterilize the reliquary after the 1988 sampling operation. Thymol is a phenolic compound that will react with many functional groups on the Shroud. This will confuse image analyses, and it may result in damage to the cloth. As one example, we found a significant amount of iron in the Shroud’s cloth. Iron reacts with phenolic compounds to form complexes, and some of them are intensely colored. I would urge the custodians of the Shroud to consult with chemists before taking other irreversible actions.
One justification for the hurried, secretive restoration was a fear of "autocatalytic" degradation of the cloth. No experts on chemical kinetics were consulted. The Shroud has not been and is not now in danger of autocatalytic degradation (see FAQ 6).
Chemical autocatalysis is responsible for the destruction of books that are made with cheap, acid paper. Claiming analogy with the Shroud is mischievous. Adler and Schwalbe made the following comment: "Previous chemical reactions on the cloth, e.g., the retting process in manufacture of the linen, the known historic fire and its extinguishment, and previous display and storage procedures, have left a variety of chemical structures on the surface that can act as oxidants and also as catalysts. For example, the acidic structures produced by previous oxidative activity can strongly promote various types of autocatalysis" [A. D. Adler and L. A. Schwalbe, "Conservation of the Shroud of Turin," Shroud Spectrum International, No. 42, December 1993, Indiana Center for Shroud Studies]. Such claims led to the secret restoration. Secrecy is neverproductive, and the plans for a restoration should have been reviewed with as large a group of scientists as possible. The restoration was a terrible mistake.