| Thanks Marek. I like your expanded answer better than Sandy's. :) Interesting point, too, about the layer of gum possibly providing a barrier to pollutants. I hadn't thought of that. I was actually surprised that someone would ask-- and I honestly didn't have a very good answer at the time. So this helps, for next time-- and I'm sure there will be a next time . . .
Diana
On Dec 20, 2007, at 2:16 PM, Marek Matusz wrote: Diana,
Platinum is a very "noble" metal and virtually indestructible, hence one might conclude that an image made of platinum is the very permanent. However there is another consideration, in fact mentioned by M Ware in his chrysotype article (I do not have a reference at hand). Platinum is a catalytic element used in a number of industrial applications and it is possible that some of the elemental degradation observed in photographs and caused by industrial pollutants like SO2 and NOX can be catalyzed by platinum. This could acidify and damage paper base, rather then the platinum itself. Some of the earlier 20th century platinum prints that I have seen do not look all that great, but I would ascribe that to poor quality paper and/or very harsh processing conditions(like use of hydrochloric acid for clearing).
SO to answer your question I would say gum over platinum is just as archival as platinum itself, maybe even better as the layer of gum might provide some barrier to the environmental pollutants.
WHen I mention gum I assume that lightfast pigments are used (like carbon black).
Sandy gave a good one sentence summary, but I though I would expand on it.
Marek Matusz
Date: Thu, 20 Dec 2007 13:27:08 -0500
From: sanking@clemson.edu
Subject: Re: archivalness of gum
To: alt-photo-process-l@usask.ca
Diana,
In fact gum (and carbon also) are probably more permanent than platinum, assuming one uses light fast pigments. Carbon pigment is totally inert, and a print that consists of carbon pigment in a hardened layer of gum arabic or gelatin would be limited in terms of life more by the support on which the print is placed than the image itself.
Sandy King
At 12:03 PM -0500 12/20/07, Diana Bloomfield wrote: Hey Chris-- Isn't platinum the most archival process? At least, that's what I always tell people. I'm sure I read that somewhere. I did have someone ask me an interesting question recently that I never thought to ask anybody-- but I had made a gum over platinum print, and this person suggested that by using gum over the platinum, I was harming the platinum in some way-- or, at least, somehow removing the archival nature of the platinum, since-- this person said-- gum isn't archival. I think this person was only *assuming* that gum isn't archival-- really didn't know for sure-- but I thought it was an interesting question.
On Dec 20, 2007, at 10:30 AM, Christina Z. Anderson wrote:
Good morning all! This may be a question for Gawain Weaver as I don't know who else on the list is "in the know". I have always read/thought/been told that gum along with carbon is the most archival process there is. I heard a comment the other day from a museum curator who said it was "not the most archival process". Now, I know that certain pigments used in the past were NOT lightfast. Gamboge, alizarin crimson, etc. were pigments that faded thru time we now know and the watercolor painters know, too. Also, I know that if you leave the dichromate stain in as a darker brown addition underneath the gum layer, through time in sunlight that image will fade to gossamer green and therefore the print will lighten **somewhat** (found a cute little article on that fact about gum prints "fading on the walls of exhibitions"). But if using archival pigments and also taking into account the slight tone difference of an added dichromate stain now that we are not cooking our prints with heavy 100% sodium dichromates, etc.,, aren't gum prints really archival?? Anyone have gum prints that have not lasted? I've seen Kuehn's and Demachy's but unfortunately, photography is a relatively new art and thus we only have about 170 years of evidence. Unfortunately, I left my only conservation book (thanks, Gawain) at home and I am in FL for 3 wk--writing my gum book at least! Chris Christina Z. Anderson
Assistant Professor
Photo Option Coordinator
Montana State University
Box 173350
Bozeman, MT 59717
406.994.6219
CZAphotography.com
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