The following article from Approfondimento Sindone isreprinted with the permission of the publisher. Copyright © 1998by Centro Studi Medievali (Pontremoli MS, Italy). Nothing may becopied or reproduced in any form without the written permission ofthe publisher.

Red Ochre and Vermilion on Shroud Tapes?

WALTER C. McCRONE
McCrone Research Institute
Chicago, Illinois

Although the 1988 carbon-14 date confirms a medieval origin, Ireached that conclusion a decade earlier on the basis of polarizedlight microscopy1. The scientific controversy over the Shroud ofTurin is unusual in its disparity of opinions, the one-sidedness ofthose opinions, and its nearly seventeen-year length2.

The Shroud of Turin, a linen cloth measuring 1.1 x 4.3 m., depictstwo images, back and front views, of a naked crucified man. A groupof scientists from the Shroud of Turin Research Project (STURP) spentfive days and nights in Turin in October 1978 examining the Shroud.These scientists identified the Turin Shroud image as blood andoxidized/dehydrated cellulose3. I, instead, found no blood andestablished the presence of Fe2O3.xH2O and HgS corresponding to twocommon artist's pigments of the 14th century, red ochre andvermilion, with a collagen (gelatin) tempera binder. My microscopicalstudies were made on thousands of fibers and particles on the 32Shroud tapes, each about 5 cm2 in area. These tapes retained surfaceparticles and fibers from body-image, bloodstain, scorch, water stainand control areas.

To the unaided eye, the Shroud image is yellow to orange in mostbody-image areas, but red in blood-image areas. Microscopically, theimage consists of yellow fibers and red particles; the red particlesare more abundant in the red blood images, and the yellow fibers arethe major colored substance in the body image. A carefulmicroscopical survey of the 22 image tapes and 10 nonimage tapesshows, without exception, tiny red particles in body- and blood-imageareas but no red particles on the fibers in the nonimage areas. Thered particles require careful high-magnification light microscopy(600-1000x) to see and identify. The results of my studies are basedon a total count of more than 8000 fibers on image and nonimagetapes. There are 10-26% yellow fibers in non-image areas and 29-72%yellow fibers in image areas.

The red particles are found on the fibers of all image tapes andhave varying degrees of hydration, color, and refractive index (fromabout 2.5 to 3.01). These properties are characteristic of theartist's earth pigment, red ochre4. Common worldwide, this pigmenthas been used by artists for at least 30,000 years. The highestrefractive index particles are hydrous, crystalline, highlybirefringent hematite with indices of 2.78 and 3.01. The iron earthpigments are hydrous iron oxide ranging in color and refractive indexfrom yellow ochre to red ochre depending on their history. Thisraises the refractive index and may result in crystallization ofhematite, anhydrous Fe2O3. A significant proportion of the Shroud redochre is hematite, thus accounting for the observed birefringence ofmany of the individual particles. The composition of the Shroud redochre was confirmed both by electron microprobe and by X-raydiffraction5. The XRD data were obtained on single red particleweighing only <1 ng of which possibly 0.2-0.3 ng is pigment. Lessthan one-half of the pigment aggregate particle is crystalline(hematite and vermilion), hence the lines in the XRD pattern are veryspotty and difficult to measure. The agreement with known hematitedata is, nonetheless, convincing.

The blood-image areas show incrustations of red substance withindications of «spalling». Many loose particles aggregates,picked from the blood-image tapes, show red particles different inshape and in color from red ochre, but characteristic of the artist'spigment, vermilion (HgS). The most common vermilion pigment is groundmineral cinnabar. The other two are synthetic mercuric sulfides, onea modern wet-process product, and the other, a dry-process form firstprepared by alchemists about 800 A.D. The chemical composition ofthis second red pigment was established by polarized light microscopy(PLM), by electron microprobe, by XRD, and microchemically. The PLMmicrochemical test requires wet ashing of one of the blood-imagesherds to remove the organic binder, dissolution of the Hgs crystalsin HIO3, and precipitation of a mercury mirror with metallic copper.All of this is done in a <100 m m diameter droplet on a copperpenny as a source for copper. The XRD pattern identified hematite inthis blood-image sherd and also showed the strongest lines forcinnabar, confirming vermilion. The research I have done showsvarying ratios for the two different pigments, and proves there musthave been two different paint applications, one a red ochre paint,and the other, a vermilion paint. The different paint sherds showvarying amounts of red ochre relative to vermilion; this alsosupports the application of two paints. Futhermore, no vermilionpigment particles were observed on any of thousands of body-imagetape fibers. It seems therefore reasonable that the Shroud was firstpainted and then the blood images were enhanced with a vermilionpaint. The finding of HgS as an artist's pigment on the Shroud ishighly significant. One might argue that Fe2O3 could be formed byblood, but it not possible to explain HgS as vermillion except as anartist's pigment. This I find incomprehensible nonsense. There is avery simple optical test that differentiates blood from red ochre orvermilion - the Becke line test for refractive index. Blood in anyform or any organic derivative of blood has refractive indices lessthan 1.60. Red ochre and vermilion have indices nearly double that ofblood, or nearly 3.0. Observing such particles with magnifications ofat least 500 times differentiates instantly between these twopossibilities, blood or red pigments, simply by focusing up and down.The high refractive index particles concentrate the illuminatinglight beam in the microscope like a lens and show a bright center asyou focus above best focus. Blood or any low refractive particlesshow a dark center under the same focusing conditions. On examiningthousands of red image particles on the Shroud tapes, I saw no lowrefractive red partides except rose madder particles and a few redsilk fibers (from the Shroud wrapping cloth). None of the redimage-area particles are soluble in hydrazine.

If the image on the Shroud is a painting, we must find a paintmedium. On one tape I observed two fibers «cemented»together with a yellowed residue. Further examination by PLM at200-400x shows paint residues on a number of fibers and very thinpaint layers stripped from the fiber surfaces by the tape lifts.Therefore, I decided to test the image fibers for paint media (dryingoils, gums, tempera) and blood using microhistological stainingreactions. Tests for protein, using amido black as well as fuchsin,show thin stained paint residues, and occasional accumulations ofpaint on the image-area fibers from several image tapes. In many ofthese accumulations, red pigment particles are observed; the collagenis stained blue with amido black, and a hint of red pigment is stillapparent within the sherd.

I think that the medieval artist6 thought about a shroud image interms of a dark tomb. Instead of the usual portrait with normal lightand shadow, he assumed that the image could only be produced by bodycontact with the cloth. This would explain the appearance of theshroud image and, as well, STURP's 3-D image contruction7. The artistpainted directly on the cloth to image the body-contact points(forehead, bridge of the nose, cheekbones, mustache, beard, over theentire body, front, and back. See fig. 3-4). This automaticallycreates a negative image; areas that normally catch available lightand appear bright, like the bridge of the nose, would instead all bedark.

I have also found a chapter entitled «Practice of PaintingGenerally During the XIVth Century» in an 1847 book, in whichthe author refers to the process as the English or German mode ofpainting faint images. «Among other methods, common on this sideof the Alps, may be mentioned the cloth-painting of the English andGermans, and their peculiar process in tempera. ... In the Trevisorecord, ... mention is made of a German mode of painting (in watercolours) on cloth. This branch of art seems to have been practiced ona large scale in England during the XIVth century ... Yet, after thislinen is painted, its thinness is no more obscured than if it was notpainted at all, as the colours have no body ... In the beginning ofthe XVth century, the ordinary tempera painting on cloth wascertainly common in the Netherlands ... The peculiarity of theEnglish method appears to have been its absolute transparency; ... Asregards to English and German paintings on cloth, there can be littledoubt that the thinness of execution for which they were remarkable,though it did not preclude gilding, was adopted with a view todurability. ... Vermilion, minium, lake, ochre, and 'face brown red',are mentioned in the Strassburg MS.»8.

Some STURP authors admit that the Shroud has protein Fe2O3, andHgs in image areas, but attribute the protein to blood, the ironoxide to retting of the flax to form linen fibers, and the vermillionto contact of the Shroud with painted replicas. Many members ofSTURP, and others convinced of the athenticity of the Shroud, explainaway the carbon dating result by invoking impure linen samples or achange in the date induced by the resurrection. They do not take intoconsideration, for example, the weight of the Shroud. The Shroudweights about 20 pounds (9 kg.); approximatley 40 pounds (18 kg.) of20th century carbon contaminant (mold, mildew, bacteria etc.) wouldbe required to raise the measured carbon date to 14th century. Aftermultiple analisys, careful calibration, and statistical calculations,these are the dates given by the three laboratories of Oxford, Tucsonand Zurich of the four samples carbon dated:

(Sample 1). Threads removed from the cape of St. Louis d'Anjou from the Basilica of Saint-Maximin, Var, France, known to date during the reign of King Phillipe IV (1290-1310). The average of 13 tests yielded a carbon-date of 1273 A.D.

(Sample 2). Linen from an early second century C.E. mummy of Cleopatra from Thebes dated by independent means to 60 B.C. The average of 11 measurements yielded a carbon-date of 35 A.D. (Sample 3). Linen from a tomb at Qasr Ibrim in Nubia, Egypt dated to the 11-12 centuries, A.D. The carbon-date, an average of 13 measurements, is 1093 A.D.

(Sample 4). The Shroud of Turin yielded a date of 1325 A.D. the average of 12 measurements at the three different laboratories.

The good agreement between the three laboratories and between thereplicate measurements at each laboratory, the careful cleaningprocedures, the experimental procedures, and the detailedcalibrations and conservative statistical analyses of the datadecribed in the 21-author Nature paper has earned the confidence ofall objective scientists. As for others, there is nothing that can besaid or done to convince them the 1325 date is undoubtedly correct. Asecond set of samples and a second carbon-dating will be a waste oftime and effort even though it will certainly agree with the 1988/89result.

The STURP scientists find no pigment particles at 20-50x (I used400-2500x). They find no cementation of the fibers nor evidence ofcapillary flow. There is no way, at 50x, that anyone could recongnizethe red particles as Fe2O3 and as red ochre or the HgS as a ninthcentury vermilion, and no way anyone could see that the pigmentparticles are cemented into an organic matrix and to the fibers. Theamounts of pigments and medium on the body-image areas and some ofthe blood-image areas, barely visible microscopically, demonstratethat the absorption spectroscopy on 1-cm2 areas by Pellicori9 andothers could not have detected them. Heller and Adler10 acknowledgethe existence of Fe2O3 and Hgs in blood image areas. Accetta andBaumgart11 state that «Shroud blood comparison with knownbloodstains show marked differences.» As I stand accused ofmisinterpreting (my) otherwise good data, I see that, at least, I amnot alone.

NOTES

1 W.C. McCRONE, C. SKIRIUS, Light Microscopical Studies of theTurin 'Shroud', Microsope, 28, pp. 105-112, 1980. W.C. McCRONE etal., ibid., 29, pp. 19-38, 1981. See also W.C. McCRONE et al., AnnArbour Science Publishers, I, 1973 and V, 1979.

2 See W.C. McCRONE, Judgement Day for the Turin Shroud, Chicago1996.

3 L.A. SCHWALBE, R.N ROGERS, Anal. Chim. Acta 1982, 135, 3.

4 R. HARLEY, Artist's Pigments, London 1970, p. 122 and R.J.GETTENS, G.L. STOUT, Painting Materials, New York 1966, pp. 8, 25-26,69-70.

5 W.C. McCRONE et al., Microsope, 29, p. 19, 1981

6 «cunningly painted as attested by the artist who hadpainted it», see H. THURSTON, «Memorandum of Pierred'Arcis», The Month, 101, pp. 17-29, 1903. It is also quoted inI. WILSON, The Shroud of Turin, New York 1978, p. 231.

7 E.J. JUMPER, R.W. MOTTERN, Appl. Opt., 19, 1909, 1980.

8 C.L. EASTLAKE, Methods and Materials of Painting of the GreatSchools and Masters, chapter V, London 1847, (reprinted New York1960), pp. 94-112 and p. 448.

9 S.F. PELLICORI, Appl. Opt., 19, 1913, 1980, see also F. FEIGL,V. AUGER, Spot Tests in Organic Analysis, New York 1966.

10 J.H. HELLER, A.D. ADLER, Can. Soc. Forensic Sci., 14, 81, 1981.11 J.S. ACCETTA, J.S. BAUMGART, Appl. Opt., 19, 1921, 1980.


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