From: Sarah Van Keuren (svk@steuber.com)
Date: 06/27/00-06:56:51 PM Z
>
>
> Sarah that was probably the washing soda in the detergent (arm & hammer
> specializes in washing soda which is sodium carbonate) -- it's possible
> they might even come back with tannic acid (to brown), but as far as I
> know the color is a form of prussian blue and shouldn't be more harmful
> than other paint or dye in clothing.
>
> Judy
>
> .................................................................
> | Judy Seigel, Editor >
> | World Journal of Post-Factory Photography > "HOW-TO and WHY"
> | info@post-factory.org >
> | <http://rmp.opusis.com/postfactory/postfactory.html>
> .................................................................
Thanks, Judy. I knew it was something alkaline in the Arm and Hammer
detergent that turned the blue to yellow. Now the parts of the puzzle come
together. A while ago when you sent me the formula that recommended sodium
carbonate as an alkaline substitute for bleach or ammonia in the toning of
cyanotypes, I couldn't remember what sodium carbonate was commonly used for.
When I get a chance, I'll tear the yellowed cyanotype on cotton cloth in
half and submerge one piece in tannic acid to see if I can bring it back in
rosy brown.
Sarah Van Keuren
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