Need Advice on Thick Gum Coating

Although I am not currently involved in gum printing the current
discussion got me interested in running a test to illustrate the
concept that in gum printing the hardening of the gum is top down. So
I mixed up 100ml of a 1:1 solution of saturated potassium dichromate
and lithorgraphers 14 Baume gum, and added ten grams of lampblack to
the mix. I applied three thin coating of this to a piece of vellum
and exposed it, through the back, with one of my carbon negatives
for 30 minutes with a UV printer. Exposure for carbon would have been
on the order of 4-5 minutes but the extra density of the paper based
added about two stops of exposure.

The print is not bad. Dmax is much higher than one could get with a
single coat of gum, and yet there is a full range of tones. The only
problem is that I was not able to get a smooth coating so there are a
few streak in the print. The results were so interesting that I plan
to do some more experimenting with this kind of printing.

So, wonder if someone with more experience than me could advise as
regards the best way to mix and apply very heavily pigmented gum
emulsions using the 14 Baume lithographers gum.

Sandy
Received on Wed Apr 5 17:48:55 2006