[alt-photo] Re: Gum Bichomate used as a resist for metal printing

[Jack Brubaker]

Hardened gum will still absorb water and if there is acid in it that will
 brake down the gum. In photo gravure gelatin is used which is resistant to
the ferric chloride used to etch it. It still breaks down but slowly enough
to get an image. Ferric chloride works on copper. I doubt it would do much
to steel.
I have etched copper with painting on gelatin (with white pigment so I could
see the drawing being created) and hardening it with ammonium bichromate and
light and etching it with ferric chloride.

Jack Brubaker