CT, the image is scorch like but unlike a scorch this image was not formed by heat.
Shroud of Turin - evidence it is authentic; the real shroud of Jesus Christ
This links talks about how scorched images are fluorescent but the shroud image doesn’t which meant it was t made by a scorch method. Sturp also showed how it wasnt made by heat because of this.
On a side note even patheos.com has an article about the shroud. The young lady who started that blog was an atheist when she first started posting articles, and recently she converted to Catholicism . She recently was on Fox News either last year or the year before. It was an amazing conversion .
Shroud of Turin: Let’s include the basic facts, please