Re: archivalness of gum
Whew Ryuji, this is very esoteric though perhaps near exact. Hidden within my description is the fact that ONCE the colors were achieved, whether through a water based release or benzyl alcohol, the colors formed could be protected through some chemical path. In other words, the dyes formed could be destroyed through UV interactions (my presumption) . . . like today's sprays, which ward off UV destruction in digital prints . . . could be protected by a 'shield'. The 'shield' then was partially cleanliness via thorough washing and removal of chemicals of destruction like the thiosulfates, but it was also the formaldehyde, which hardened the dye cloud, protecting it. My theory, which seems to be substantiated due to the 1960's images being still here and with not bad color though kept in drawers, is that I used then a hypo-eliminator and washed twice as long and hardened w/formalin (which, oddly, I still have). Best Jack On December2007, at 10:37 PM, Ryuji Suzuki wrote: From: jfulton <jfulton@sfai.edu> Subject: Re: archivalness of gum Date: Thu, 20 Dec 2007 15:09:55 -0800the Agfa color paper I had used, which was a Type B VS Kodak's Type A material, was the worst ever in the history of color photography for fading etc. [...] there once was two 'types' of color paper: Kodak's w/an encapsulated color coupler released by benzyl alcohol as I remember and the Agfa type that was water based. The water based material faded quickly. I wonder if they made it today, like our greatly improved latex paints, if they might last longer and be safer to the environment.The short answer is they probably don't want to make such materials using water dispersible couplers. The water dispersible couplers are, due to their molecular structural limitations, difficult to make such that the dyes formed will have nicely narrow spectral absorption characteristics. They are also difficult to synthesize and particularly purify. Inferior permanence would be largely the same as what you experienced, as well, though this one might be possible to improve it if they try. There is another type of couplers, that are sometimes used for magenta couplers. The couplers are immobilized by polymerization. The solvents used to disperse oil-soluble couplers are almost completely recycled within the film factory. Some organic solvents of high boiling point are used to disperse the couplers, and then this dispersed coupler is emulsified in the base silver gelatin emulsion using dispersants/emulsifiers/surfactants. Therefore, overall, the vast majority of the solvents is water. -- 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)
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