RE: possible answer to archivalness comparison between carbon gum andpt/pd
However, I might mention than when I visited the Societe de Francais Photographie in Paris I was allowed,as a member, to view some prints in their collection. There I saw some gum prints in color by Demachy that were to die for, that showed no evidence of fading.Which could also have been because the Demachy's were stored in the society archive under ideal (or perfect !) conditions.
But I repeat what I've said here before... We obsess about archivality because we're afraid photography isn't "real" art. "Real" artists do no such thing -- they smear house paint, or mud, or finger paint on whatever paper or cardboard or the back of an envelope or a placemat at the local pizzaria & the collectors fight for them.
Has anyone ever heard a question about whether R. Crumb's drawings on placemats, or Rauschenberg's "combines" or stuffed goat or thousands of others I'm not thinking of right now are "archival"? (In fact I read a
recent admiring review in either Artforum or Art in America of a show in which yellowing and cracking of age had been artfully contrived...)
In these media, patina of age is, as noted, either an added value or simply a fact of life (or time) & not a problem. So what is our problem ? True, you don't want a photograph to fade *noticeably* in your lifetime, but to worry about whether platinum is more "archival" than gum, or vice versa, is ...... unnecessary.
(And IMO caused by brain washing... which may be the "correct" washing mentioned.)