John Brown, principal research scientist at Georgia Tech Research Institute, studied some threads from the Raes sample and found evidence of cotton threads with dye applied to it. Where the threads crossed, there was not any dye.
Figure 1 shows a weft thread, R7, at an original magnification of 28X. The thread has a yellow-brown coating with the exception of indented regions which are white. These indented regions are at the intersection with the warp thread. The weave was tight enough that the application of a relatively viscous gum/mordant/dye solution did not penetrate the intersection of the threads. This would appear to be obvious evidence of a medieval artisan’s attempt to dye a newly added repair region of fabric to match the aged appearance of the remainder of the Shroud. Figure 2 shows the same thread at 56X magnification. The coating and encrustations can be seen on individual fibers.
https://www.shroud.com/pdfs/brown1.pdf
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