RE: possible answer to archivalness comparison between carbon gum andpt/pd
I too have looked at a fair sample of historic carbon prints and have never seen this problem -- not even a smattering of crazing have I observed. I suspect it has more to do with the support surface than the carbon itself. You can put a carbon print on virtually anything that will hold still long enough. And there were dozens of final support materials available, and if one of those was to have its supporting surface craze, I would suspect it would affect the image on the surface as well. -----Original Message----- From: Sandy King [mailto:sanking@clemson.edu] Sent: Friday, February 29, 2008 7:09 PM To: alt-photo-process-l@usask.ca Subject: Re: possible answer to archivalness comparison between carbon gum and pt/pd OK, but I have seen a lot of vintage carbo prints, in Spain, France, the UK and in the US. I have never seen one with gelatin *crazing*. I know that it must exist because Reilly mentions it. But I have never, ever, seen it. So there. I don't accept your strike against carbon. Sandy King At 6:37 PM -0700 2/29/08, Christina Z. Anderson wrote: >I was at the library today and came across Reilly's book Care and >Identification of 19th century photographs. It was published in >1986, so the information could be outdated, and I bet Gawain Weaver >on the list could say what is and isn't still true. > >What I found in there was surprising. It said that platinum was >"exceptionally" archival, however, the agents we use to develop and >clear wreak havoc with the paper and thus the support turns yellow >or whatnot even though the pt/pd layer itself is archival. The >image is permanent and unchanging even though ghosting occurs--the >ghosting is a catalytic action that affects the paper in contact >with the print but not the pt/pd layer itself. This catalytic >action does, though, affect the paper support itself as well, >embrittling it or discoloring it. In other words, the pt/pd metallic >layer is not the issue, but the paper it is on is and that is >affected by developers and clears as well as the hastened catalytic >action of the pt/pd. > >Now, carbon (this is what blew me away) is exceptionally archival >also, but the main problem is cracking of the gelatin layers where >they are thickest--in the shadow areas of the print. Reilly says >since the gum layer in the shadows is not as thick as the >carbon/gelatin layer, this is seldom an issue with gum prints. And >gum prints have "excellent image stability". > >So one strike against pt/pd, one against carbon, none against gum... > >That's all for now, going to go read my brand new copy that just >arrived from Amazon of Christopher James' new book the Book of >Alternative Photographic Processes. I see a lot of names in there I >recognize!!! :) >Chris > > > >Christina Z. Anderson >Assistant Professor >Photo Option Coordinator >Montana State University >CZAphotography.com >_______________
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