[alt-photo] Re: gelatin modification

[Ryuji Suzuki]

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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