U of S | Mailing List Archive | alt-photo-process-l | Re: possible answer to archivalness comparison between carbon gum andp

Re: possible answer to archivalness comparison between carbon gum andpt/pd

From: Gawain Weaver <gawain.weaver@gmail.com>
Subject: Re: possible answer to archivalness comparison between carbon gum and pt/pd
Date: Sat, 01 Mar 2008 08:04:31 -0500

> however, as was pointed out in the last archival go-around,
> archivalness is not a useful measure when speaking of the
> permanence qualities of various processes, and I don't think
> there can be any one correct answer to the question

I agree. I think the way I said is that "archivalness" is not
a single variable measure that you can compare among different
processes or materials. This is because each process or
material has its own archival weakness that may be different
from those of other processes. It is a lot more constructive
to know the weakness of your process, and then how best to
protect the work from it.

I have no experience with carbon prints, but I can say
something about gelatin. Gelatin becomes very brittle and easy
to crack when kept in extremely dry condition, and
particularly dry and warm condition. If the gelatin is loaded
with pigment or other matters, the gelatin may be even easier
to crack.

Gelatin is not a single substance. It is a processed animal
product that comes in a hugely wide range of grades and
qualities, and only some of them are characterized (such as
average molecular weight, bloom strength, hide/bone gelatin,
acid/lime extraction, extraction number, etc.) It is easily
conceivable that some of these variables are highly correlated
with the tendency of the gelatin to crack.

Another thing about gelatin is that you can use a small amount
of gelatin plasticizer, such as dextran, sorbitol, poly(vinyl
pyrrolidone) and its copolymers, cellulose derivatives, starch
derivatives, glycols, glycerols, etc. to prevent gelatin from
becoming brittle in dry conditions. Some of these are used for
silver gelatin material in the past and/or present, that is,
there is no other harm if used correctly. In silver gelatin
materials, selection of suitable plasticizer is a rather
tricky business, since many of these things make gelatin film
swell excessively in processing chemicals, and also because
some of these plasticizers are removed by wet processing
thereby losing the needed effect when prints are
stored. However, selecting a plasticizer for processes where
gelatin layer is never subjected to wet processing is much

Residual iron in paper can be very harmful. Iron is a very
effective catalyst to generate hydroxyl radical, which is a
very strong oxidizing agent and it is known to attack
cellulose. If I used iron-based processes, I would definitely
test for complete removal of iron, and think about ways to
ensure complete removal of it from the paper, or at least ways
to inactivate iron if complete removal is difficult.

Ryuji Suzuki
"Make something religious and people don't have to deal with it, they
can say it's irrelevant." (Bob Dylan, Biograph booklet, 1985)