[alt-photo] Re: gelatin modification

[Marek Matusz]

Thanks

It will get me started

Marek
 
> Date: Thu, 6 May 2010 20:30:27 -0400
> To: alt-photo-process-list at lists.altphotolist.org
> From: rs at silvergrain.org
> Subject: [alt-photo] Re: gelatin modification
> 
> Sure, I'll dig my notes. Wasn't it on my website?
> 
> Quick response based on my memory alone.
> 
> Disperse the gelatin in water, hold the kettle at 40C, at pH
> 10 using NaOH. Do not use any buffer. Just adjust with pH
> meter and add NaOH in small portions as needed.
> 
> Prepare phthalic anhydride solution in dry acetone, forgot
> concentration but 10% or higher, and the amount is determined
> in relation to the gelatin's dry weight. While stirring the
> kettle, add a predetermined amount of phthalic anhydride
> solution, drop by drop, and adjust the pH frequently.
> 
> Hold the kettle for some time to complete the reaction.
> 
> Chill the solution and bring the pH to 4 range to coagulate
> the gelatin. Wash the gelatin. Redisperse at pH 8-10,
> coagulate again for the second time, to wash it. Use sulfate
> salt if needed. The gelatin is good for use.
> 
> I remember I consulted several patents by Yutzy et al of
> Eastman Kodak Lab in 1950s. They included several examples,
> and if you try them all, many of them don't work. The example
> that uses NaOH and dry acetone works fine.
> 
> A better yet is another patent from Polaroid corporation,
> using trimellitic anhydride in place of phthalic anhydride.
> Those gelatins coagulate better. Also use NaOH and dry
> acetone, but the reaction pH can be a bit lower, like 9.5.
> 
> --
> Ryuji Suzuki
> "Don't play what's there, play what's not there." (Miles Davis)
> 
> 
> From: Marek Matusz <marekmatusz at hotmail.com>
> Subject: [alt-photo] Re: gelatin modification
> Date: Fri, 7 May 2010 00:16:07 +0000
> 
> > 
> > Ryuji
> > 
> > Some years ago you posted a recipe for making phtalated gelatin. At least I think it was you, as you were really interested in the chemistry of B&W.
> > 
> > I can't find it now. Could you post it back if it was your recipe in the first place.
> > 
> > Marek 
> > 
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