Re: archivalness of gum
From: jfulton <firstname.lastname@example.org>
Subject: Re: archivalness of gum
Date: Thu, 20 Dec 2007 15:09:55 -0800
> the 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
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.
"Make something religious and people don't have to deal with it, they
can say it's irrelevant." (Bob Dylan, Biograph booklet, 1985)