[alt-photo] Re: Gum printing: removing the dichromate altogether?

[Alberto Novo]

a little OT: 

> Glasses are often coloured with chromium and render it green so it is 
> often added for wine bottle glass.

True that chromium is used to make emerald green glasses. Instead, for 
bottles it is iron, usually already present as an impurity, making it green 
or brown depending on reducing/oxidizing environment of the furnace.
See http://1st-glass.1st-things.com/articles/glasscolouring.html 

Returning in topic:
some years ago I had a discussion with Katharine Tayer about chromium stain 
in gum bichromate, the way to wash it out and chromium residue in the print. 
I believe that she tried to contact a chemist for a chemical analysis of the 
hardened gum arabic, but I don't know if she had any results back. 

Alberto
www.grupponamias.com
www.alternativephotography.com/wp/photographers/rodolfo-namias-group