Re: gum bichromate
Virginia Boehm (email@example.com)
Sun, 11 Jun 1995 15:22:08 -0700
>Materials: Saturated pot dichromate solution- 1 year old, stored in
>in brown glass bottle. 'Gloy' gum - described by manufacturers
(Henkel) as gum
>adhesive suitable for card and paper applications - also 1 year old.
>Newton 'Cotman' water colour paper. Winsor and Newton water colour
>I first size the paper and dry it - usually with a hot hair dryer.
>weak tungsten light, I make just enough emulsion for immediate use, by
>equal volumes of dichromate and gum with varying quantities of water
>paint and apply it to the paper with a paint brush. I have been drying
>a dark room by placing it in a empty developing dish on a warm
>seems from what has already been written that this is probably not a
>I then expose the paper through a negative to a uv sunlamp. Previously
>exposures between 30 seconds and 3 minutes worked. They don't now! I
>'develop' the image in warm water by gentle brushing with a paint
>Does sunlight give better results? Problem is that sunlight is not
>avaliable here! What about negative quality ie does the process work
>high or low contrast negative? Are there better materials I could be
> Thanks again for your help
What you describe is a very standard procedure for gum and why it
worked for you a year ago and doesn't now is puzzling. The only thing
I can think of is the gum (which is one I'm not familiar with) is one
with poor keeping qualities. Does it smell fresh? I've had gum go
sour on me and it smells. You might try gum arabic. From what I
gather, the bichromate doesn't wash off. YOu might try warmer water.
Let your print float emulsion side down in the water for a few minutes.
Yellow from the dichromate should start to stain the water. Then, if
you want to speed things up using the paintbrush go ahead. But let the
process start first. Let us know how it works out.