Steven Avery
Administrator
I am not aware that old vellum/parchment takes on color because of age.
Here is Scrivener:
A full Collation of the Codex Sinaiticus with the received text of the New Textament (1864)
https://books.google.com/books?id=v-JUmBD5zIcC&pg=PP38
"The vellum leaves, now almost yellow in colour ..."
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The Primitive Methodist Magazine (1872)
Introduction to the Study of the New Testament
James Austin Bastow
https://books.google.com/books?id=zwkFAAAAQAAJ&pg=PA234
"parchment, supposed to he made of antelope skins, but it is now quite yellow with age."
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Additional info:
https://forums.carm.org/threads/the...nides-regarding-sinaiticus.11880/post-1248652
Detecting Forgery: Forensic Investigation of Documents (2015 and 2021)
Joe Nickell
https://books.google.com/books?id=A0wgEAAAQBAJ&pg=PT254
Joe Nickell, forgery detector, tells how:
Brown staining of a document suspected of having been aged with tea can be tested by a saturated solution of hydrated ferrous sulfate, which will cause tea stains to turn black. Of course, as discussed in chapter 5, other substances have been used to give the appearance of age,