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weft
weft is the term for the yarn which is passed over and under the warp yarn. A device called a shuttle is usually used to move the weft yarn over and under the warp yarn. By varying the number of warp threads passed over or under (for instance over one, under two, and so forth), and varying the starting point, different patterns of cloth can be created. Such patterns are called twill. Examples of twill include gabardine, tweed, serge and herringbone.
In the ancient production of linen on vertical hand looms, warp yarns (threads) were the up and down threads on the loom. They were often lubricated with crude starch to make it easier to weave the weft threads over and under the warp threads.
Yarn is the preferred term for thread used in weaving, although the word thread is perfectly acceptable. Yarn is formed by spinning or twisting together fibers (fibres) from plants, animals or in the modern era, extruded or chemically produced materials.
Animal Fibers (fibres) include silk, sinew and wool. Plant fibers include cotton, hemp and flax. The yarn used in the Shroud of Turin is made from flax. The thickness of the flax fibers varies significantly but the average is about 13 micrometers or roughly one-eighth the thickness of typical human hair. The Shroud’s yarn (thread) consists of approximately 70 to 120 flax fibers hand spun together in a Z-twist (clockwise). Counterclockwise spinning is referred to as an S-twist.
Variegated patterns of whiteness in both the warp and weft yarn indicate that the yarn was bleached before weaving rather than after the cloth was taken from the loom. This was common prior to the medieval era but not the common method of bleaching linen in medieval Europe where the cloth was sun bleached in “bleaching fields.”
The residue coating of starch fractions and saccharides on the outermost fibers is consistent with an evaporation concentration. This is the sort of residue that forms when trace amounts of these substances in rinse water are moved to the surface as water wicks to the outside of a cloth as it dries. The saccharides in the coating are like those found in Soapwort (saponaria officinalis). These include glucose, fucose, galactose, arabinose, xylose, rhamnose, and glucuronic acid). This coating is about 1 percent to 4 percent of the thickness of the fibers. Where there is image color, the color is completely within, and the result of a caramel-like chemical change to, the otherwise clear evaporation concentration layer.
The residue coating is expected from first century methods of linen manufacturing described by the historian Pliny the Elder. Because the warp threads on the loom were coated with starch as a lubricant, the cloth was then rinsed with soapwort to remove the starch and laid out to dry. The bleaching of hanks of yarn before weaving is also consistent with first century methods but not consistent with medieval European field bleaching of finished cloth.
Shroud of Turin Story
© 2005 Daniel R. Porter, Bronxville, New York
