What is banding and why is it important?
There are visually apparent vertical and horizontal bands of darker and lighter color throughout the entire cloth. Some of the bands are thick. Others are thin. Some run the entire length or width of the cloth and others do not. The bands are not very pronounced and are almost unnoticeable to the naked eye. But they appear clearly in photographs of the Shroud. And this presents a problem for studying images on the Shroud.
When the photographs are enhanced to draw out faint images, the bands are enhanced as well. In a sense the background is like a faded Tartan cloth. Tartan is made with alternating bands of colored (pre-dyed) threads woven at right angles to each other. But the comparison ends there. The lines of the banding on the Shroud are very irregular, muted and subtle. They are simply visual noise.
An example of how dramatically the banding influences visual interpretation of the images is its effects on the face. The face appears gaunt and the nose seems very narrow and long. This is influenced by the banding. If we look carefully we see that the gaunt appearance is the result of dark vertical bands on each side of the face and on each side of the nose.
Banding, along with other visual noise, certainly affects identification of many things that people believe they see on the Shroud. This includes the appearance of coins over the eyes, inscriptions, plant and flower images and a number of other things that people claim to see.
It has been suggested that the banding is the result of how the threads of the cloth were bleached in a method known as hank bleaching. If this is the case, it is most unlikely that the linen cloth used for the Shroud was produced in medieval Europe. Such cloth was field bleached after weaving. Medieval European linen was not hank-bleached. The woven cloth was soaked in hot lye solution, washed, soaked in sour milk and washed again. Following this treatment it was spread out in fields in the sun. This process eliminates variegation.
In hank bleaching, individual hanks (lengths of thread or yarn) are bleached before weaving, usually with potash. Because this is not a uniform method, different hanks have different degrees of bleaching and this becomes apparent after weaving as variegation.