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Re: Re: chrome alum
I beleive this is the quote you are looking for.
> chrome alum and potassium alum in preparing final support papers for
> carbon, the former for single transfer papers that have to be well
> hardened because they will be used to develop the image in hot water,
> and potassium alum for the final support paper for double transfer,
> because for this I need a gelatin that is only semi-hardened. I use
> the same amount of both of the alums for a given quantity of gelatin
> solution, about 2-3g per 1000ml of solution. If you test for
> hardening after several days by placing papers prepared with the two
> hardeners in a tray of water at about 75F, the gelatin surface of the
> paper hardened in chrome alum remains very hard, while the paper
> hardened will swell a lot and become almost slimy to the touch. Even
> after 6 months to a year the paper hardened in potassium alum will
> retain this ability to swell and become slimy to the touch.
> It would be difficult to confuse the two alums. Chrome alum looks
> like final particles of purple sand, potassium alum almost like sugar.
> Sandy King