Future Scientific Study Options Following 2002 Restoration

From Ray Rogers’ FAQ: (Answer for this question is the same as for The 1532 fire and image properties, as published)

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 never productive, 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.

Future Scientific Study Options Following 2002 Restoration

How do you know that the fire of AD 1532 did not start a long-term autocatalytic decomposition of the Turin Shroud?

From Ray Rogers’ FAQ:

Based on the facts of chemistry and current storage conditions, the Shroud of Turin is not now and has never been in imminent danger of catastrophic autocatalytic decomposition. The "restoration" of 2002 was based on an erroneous understanding of chemistry.

Autocatalytic chemical reactions are those in which the rate increases as the amounts of reactants decrease, i.e., while the materials are reacting. The most important single factor in predicting effects is the temperature. When the temperature changes, the rate changes. The only severe heating episode the Shroud has suffered was during the fire of 1532. Any autocatalytic decomposition that occurred then has long since stopped as the Shroud is stored at normal temperatures.

The fundamental chemical-rate equation that describes an autocatalytic process is the following:

where ? is the fraction reacted at any specific time, t. The derivative, d? ?dt, is the rate of the reaction. E is the "Arrhenius activation energy," and Z is the "Arrhenius pre-exponential." Each applies only to a single specific, consistent reaction being studied. The value of the "rate constant," k is different at each specific temperature: It is a constant only at one temperature, and it applies only to one specific reaction. The values of E and Z are determined from a large number of k measurements at different temperatures.. Predictions of the Shroud’s expected lifetime can not be made on the basis of a single rate constant. Observations made during a scorching event can not be applied to rates at normal temperatures.

E, Z, and k are the most important values in a discussion of rates and associated lifetimes of materials. All of these values have fundamental meaning in the chemical reaction. R is the "gas constant (1.9872)," a universal constant that applies to many disparate physical and chemical processes, and it is known with great accuracy and precision. T is the absolute temperature, expressed in degrees Kelvin (0K = -273.2?C). The exponents p and q allow the prediction of the position of the maximum rate in an autocatalytic process, i.e., the amount reacted at the maximum rate – at constant temperature. Exponents higher than 2 are extremely rare.

Examples of simple and autocatalytic rate curves are shown in the figure. Notice that the rate increases with time in the autocatalytic curve, at constant temperature, until it reaches a maximum reaction rate. Then the rate decreases. However, the initial rate at any temperature is much lower than the maximum rate. The chemical decomposition rate of cellulose is essentially zero at room temperature. Most long-term degradation of cellulose that is observed in archaeological contexts is caused by microbiological attack.

When cellulose is decomposing autocatalytically at high temperature, the rate can be returned to its initial value by cooling.

Reaction rates in solids, especially crystalline solids like cellulose, are much lower than the values for the same material in a solution or melt, because a crystalline lattice is stabilized by its ordered structure. The crystal structure is called "fibrillar" in materials like linen.

A major cause for autocatalysis in cellulose decomposition is the destruction of crystalline order when the material is heated above its melting point, about 260^ºC. With the exception of the fire of 1532, the Shroud has never faced this danger. Secondary, chemical autocatalysis is discussed below. Rates in the normal cellulose solid phase are essentially zero in the absence of acids, bases, short-wavelength light, or water and microorganisms.

When the crystalline order of cellulose is destroyed by heating, the cellulose melt is also chemically autocatalytic. The possibility for chemical autocatalysis in linen depends on the products of cellulose decomposition. Feigl and Anger [Feigl, F. and Anger, V., 1966, Spot Tests in Organic Analysis, Elsevier Pub. Co., New York.] describe the effects of heating cellulose as follows: "When cellulose is heated it decomposes and the resulting superheated steam reacts with unchanged cellulose to produce hexoses, which in turn hydrolyze to give hydroxymethylfurfural." The only important chemical catalyst for the autocatalytic degradation of cellulose at high temperatures is superheated steam. Superheated steam does not exist at room temperature. There is no "memory effect." The Shroud should be as stable at room temperature as any other sample of linen. The Shroud was in no danger of autocatalytic decomposition.

The decomposition rate of a crystalline solid depends on crystal perfection. When crystals are put under stress, they develop high-free-energy defects, and decomposition is much faster at the defects than it is in the parent material. If autocatalysis were a real problem for the Shroud, significant differences should have been observed around the stressed and strained stitching of the patches. STURP observed those areas, and there was no sign of accelerated autocatalysis, indeed there is no sign of any autocatalysis. Autocatalysis is not a real hazard for the Shroud.

More detailed studies have shown that the major or secondary products of the thermal decomposition of cellulose are formaldehyde, furfural (2-furaldehyde), hydroxymethylfurfural (5-hydroxymethyl-2-furaldehyde), levulinic acid (4-oxopentanoic acid), and 3-pentenoic-?-anhydride. None of these are a significant catalyst for the autocatalytic decomposition of linen. Indeed, formaldehyde, furfural, and hydroxymethylfurfural are reducing agents, antioxidants. Furfural inhibits the growth of molds and yeasts. Scorched areas are less likely to show microbiological attack.

Observations and descriptions of the Shroud through the 470 years since the fire of 1532 do not support fear of catastrophic decomposition of the cloth. There is absolutely no evidence for attack on the cloth by acids, bases, or microorganisms. Samples from all parts of the Shroud were tested for pH by STURP. No impurities that could start autocatalytic decomposition were found, confirming what was observed through the 470 years of history.

If Shroud deterioration is still a worry, one practical way to slow the rate is to keep it cold. That also has the advantage of reducing microbiological attack. As in the case of the use of "inert" atmospheres, storage at reduced temperature should carefully be considered. Too low a temperature could cause physical stress and might cause fibers to fracture. It would probably cause the thin coating of image color on the fibers to be loosened in some areas.

As a rule of thumb according to the Arrhenius expression, rates of normal reactions are increased by a factor between two and three for each 10?C increase in temperature. Some moderate cooling could have a significant effect on prolonging the life of the Shroud. Severe freezing could damage the cloth and image.

Fire of 1532 Did Not Start Long-Term Autocatalytic Decomposition