U of S | Mailing List Archive | alt-photo-process-l | Re: bichromate gum

Re: bichromate gum

I never buy reagent grade chemicals and do just fine. I also have used all three dichromates and they're all fine except sodium is sooo saturatable that you can mix it over 100% and get a honey like consistency.

Speaking of the painterly approach to gum, one of the highlights of my stay at George Eastman House was seeing prints that had the brushed on colors as you say. One guy did the base exposure in a neutral color (not black, but a greyish putty color mixed from different watercolors) and exposed a lightly pigmented and long exposure layer first to get all the pix detail, then came back in and brushed different colors on in different areas. It was quite fun. I wonder if you couldn't try to do that, and paint your dichromate only layer on top of the putty layer, below and then brush on the different colors hither and thither and then expose?
----- Original Message ----- From: "Don Sweet" <don@sweetlegal.co.nz>
To: <alt-photo-process-l@usask.ca>
Sent: Thursday, July 10, 2008 6:48 PM
Subject: Re: bichromate gum

Thanks to Sam, Christina and Judy for the helpful replies.

Speaking of chemical purity, my dichromate isn't exactly reagent grade - it
is sold as "sodium potassium dichromate" by the kilogram for use as a
pottery glaze. That seems to be the only way to buy it in New Zealand now.
I recently acquired some photo chemicals from an old hoarder which included
a 1oz bottle of pot dichromate with a pharmacist's logo on the label and a
price dating back to before we converted to decimal currency (1967) - the
contents had formed a single crystal Obviously in those days you could buy
stuff like that over the counter, but now we have an international
bureaucratic network dedicated to eliminating such hazards now (also
removing Portriga Rapid paper and mercury lightmeter batteries, and
replacing inert aerosol propellants with explosive ones).

One of the advantages that I thought the "bichromate first" technique might
offer is the opportunity to take a more painterly approach to the colouring
step - e.g. use more colours, follow the image a bit, and leave some blanks.
Does that make sense?

Don Sweet