Re: Re: chrome alum

[dsbryant@mindspring.com]

Chris,

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 

Don Bryant