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

Re: bichromate gum


That's actually a good way to control brush stroke patterns - take your time coating with just the dichromate first, and then the gum with pigment. This is especially useful in spray or airbrush coating of gum, so that the end result will still have the brush markings and you don't have to worry about breathing in the dichromate.

I suspect that the higher contrast is due to the reduced amount of dichromate, which would be a good thing to practice but you will need to test and make a curve to fit that.

As Judy would suggest, start with printing a step tablet and that should tell you a lot.


On Jul 7, 2008, at 5:53 PM, Don Sweet wrote:

Christopher James' new book mentions, as an untested idea, something that I
read recently in a Barnet text from about 1898, namely that you can put the
dichromate coat on after the size has hardened and leave the paper for some
time before putting the paint/gum coat. From memory the Barnet text (too
dear to buy) suggested the resulting image would be more contrasty with less
highlight details than a conventional gum print. Can anyone cast any
further light on this idea, or suggest any starting points for further
Don Sweet