There is no way the blood stains could’ve been painted on after the image was imprinted on the cloth. It’s because there is no image under the blood stains. That means the blood was on the cloth first and then the image was formed. And if you think about, it must’ve happened this way if Jesus was wrapped and then was resurrected. So, if it was a forgery, how was the artist able to put on blood stains perfectly first and then depict the image? And how was the artist smart enough to do this?
This absence of body image on the wound image margins suggests that the blood images were present on the cloth before the body image was “placed,” “appeared,” or perhaps “developed.” This suggestion is consistent with the chemistry of the body-only image, because this thinner fluid could have coated these margin fibrils sealing them and preventing the advanced decomposition reaction. This conclusion is supported by microscopic examination of the fibrils from the blood areas after removing the serum coating by protease digestion. Fibrils, so treated, more closely resemble those from the off-image olear areas than those from the body-only image areas when viewed by phase contrast microscopy.
https://pubs.acs.org/doi/10.1021/ba-1984-0205.ch022
https://debatingchristianity.com/forum/viewtopic.php?p=1105790#p1105790