The following is from pages 15 and 16 of Scientific Method Applied to the Shroud of Turin: A Review by Raymond N. Rogers and Anna Arnoldi published at shroud.com.
(D) Lignin amounts vary among Shroud locations. X-ray-transmission[4,22], contrast-enhanced, ultraviolet, and transmitted-light photographs of the Shroud all show specific, discrete bands of yarn with different x-ray densities and corresponding color densities (figure 3). Both warp and weft yarns show this property. Some areas show darker warp yarns and some show darker weft yarns. In some places bands of darker color cross. In other places bands of lighter color cross. The effect is somewhat like a plaid. Many photographs of the Shroud can be viewed on the Shroud web site: http://www.shroud.com.
Linen is bleached to remove the lignin in an attempt to render it pure white. The more quantitative the bleaching process the whiter the product. The bands of different color on the Shroud are the result of different amounts of lignin left from the bleaching process. The tape samples reflect this variation as observed differences among quantitative measurements of lignin on the fibers.16
A conservator at Turin’s Museum of Egyptology, Anna Maria Donadoni, pointed out locations where batches of yarn ended in the weave and new yarn had been inserted in order to continue weaving. The yarn ends were laid side by side, and the weave was compressed with the comb. The ends are often visible, and the overlaps appear to correspond to zones of different color in the weave.
I believe that the observations of bands of different colors agree with Pliny the Elder’s description of ancient linen-production technology. Ancient linen yarn was spun by hand on a spindle whorl. When the spindle was full, the spinner prepared a hank of yarn for bleaching by the fuller. Each hank of yarn was bleached separately, and each was a little different; indeed, different parts of the same hank show slightly different colors, a little like variegated yarn. The warp yarn was protected with starch during the weaving process, making the cloth stiff. The final cloth was washed with "struthium," Saponaria officinalis, to make it more supple.
Medieval linen was bleached as the whole cloth. Most commercial bleaching took place in "bleach fields" in the Low Countries, the genesis of the name "Holland cloth" for the Medieval backing on the Shroud. Considerable material was lost during the bleaching process, and the newer linens are less dense than ancient linens, as can be seen by comparing the Holland cloth and patches with the main part of the Shroud. The newer linens are also homogeneous. They do not show bands of different-colored yarn in the weave.
A phloroglucinol-hydrochloric-acid reagent detects vanillin (4-hydroxy-2-methoxybenzaldehyde) with great sensitivity. Fresh lignin evolves vanillin in the reagent. You can often smell the vanillin that is evolved from the lignin of warm pine-tree bark. The lignin loses vanillin with time and temperature. The lignin on older samples of linen gives progressively weaker tests for vanillin as age increases. The lignin on Shroud samples does not give the test. That fact could indicate either significant age for the Shroud or accelerated aging of the lignin as a result of heating during the fire of AD 1532. Differences between amounts of lignin on linen fibers in the Raes samples and on Shroud fibers are significant. There is probably a similar difference between the radiocarbon samples and the main part of the Shroud.
A little over a year ago a reader of this blog wrote to me saying:
I hate to inform you but Ray Rogers was wrong. Pliny the Elder never said that Saponaria officinalis was used in the bleaching of linen. What he said is, “There is another kind of wild poppy (a spurge rather, Euphorbia esula of Linnaeus), known as "heraclion" by some persons, and as "aphron" by others. The leaves of it, when seen from a distance, have all the appearance of sparrows; the root lies on the surface of the ground, and the seed has exactly the colour of foam. This plant is used for the purpose of bleaching linen cloths in summer.” — Pliny the Elder, The Natural Histories, Book 20, Chap.79
The heraclion plant is not Struthium (soapwort, Saponaria officinalis).
I wrote back at the time:
It was Theophrastus who said that struthium was used for bleaching linen. Pliny, according to some sources, misunderstood Theophrastus to mean heraclion.
Was Saponaria officinalis used for bleaching linen 2000 years ago? Yes. Do we need to correct about a million web pages at this point? Probably.
It is a bit curious where Rogers got his information.
Now as for the truth about banding. My guess is that Rogers is right; Medieval linen, particularly in Europe, was field bleached because the technology and the linen production industry had advanced by that time. How do we prove it?
There is a control. The Holland cloth which was added as backing circa 1534. It was not banded, while the Shroud in chief was.
Holland cloth as we know it today is essentially unbleached cloth with a dull finish, used as furniture covering, blinds and the like. It is made opaque by a glazed or unglazed finish, called the Holland finish, consisting of oil and a filling material. However originally it was applied to any fine plain-woven linen imported from Europe, particularly the Netherlands. Was the Holland backing cloth sewn by the Poor Clare nuns, bleached or not? I don’t know.
I was surprised to discover that the spinning wheel was a relatively late invention. The earliest clear illustrations come from Baghdad in 1237, and quickly found its way to India, although India is sometimes credited with the invention. The first spinning wheels were operated by hand, and although known in Europe by the 14th century did not come into immediate general use. By this time, the Chinese were using water power to drive their spinning wheels, but this was not developed in Europe until the 18th century. A citizen of Brunswick is said to have added the treadle in 1533, and its more general European use might well date from this improvement.
Prior to the adoption of the spinning wheel, yarn was hand-spun, by whirling a distaff holding the fibres onto a free hanging weighted spindle. However in France, the distaff and spindle were not displaced until the 18th century. Adoption of the spinning wheel meant that five spinners could keep a weaver fully occupied.
In the early Middle Ages, the main European textile centres producing linen fabrics seemed to have been in Flanders, notably Ghent, Ypres and Courtrai. Sicily and Palermo seemed to have specialised in silk around 1130. Textile specialists seemed to have been quite migratory, as a result of foreign invasions, or the later religious wars and persecutions.
English textiles in the 13th and 14th centuries were mainly linen and wool, the trade being influenced by Flemish fullers and dyers. In 1564 Queen Elizabeth I granted a charter for Dutch and Flemish settlers in Norwich, for production of damasks and flowered silks. Revocation of the Edict of Nantes in 1685 caused many weavers to migrate to England.
How might all this bear on the question of banding, and the bleaching of linen? I think it almost certain that the Flemish fullers were bleaching completed cloth, rather than just the unwoven yarn. They would require large areas of reasonably level open fields to carry this out, where the cloth to be bleached must be spread out for several months. Flanders and the Netherlands would have met this requirement. So very likely this was the method by no later than the 13th century.
The earlier slower spinning methods of distaff and spindle, might have been conducive to a production process where the unwoven yarn was bleached before weaving. The spinning wheel in the 16th century would have set the closure on any remnants of this process, if it still then persisted.
Was bleaching of unwoven yarn terminated much earlier, say in the 4th and 5th century as some have asserted? The only way of answering this question I think, is to look for the latest and most recent examples of banded linen cloth. Someone must know of any such examples, which would settle this question, once and for all.
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