gelatin hardening for gum

Yesterday and today I tested a new hardening agent for gelatin-sized
papers meant for gum bichromate printing. Looking to get away from
using formalin and glyoxal, I tried an aluminum sulphate hardener from
Sprint Systems of Photography. It is packaged as their liquid
concentrate "Record Alum Hardening Converter" and is normally used to
make hardening fixers for films and prints. I tried 60ml per liter of
water (a double concentration) and so far the results look good. I was
able to make a gum print today with a strong image layer and no
staining.

I don't know what the long term effects of using this hardener may be,
but I figure if it is OK for factory fiber gelatin silverprints it might
be OK for gum. It is also easy to acquire compared to formalin.

I treated the papers for 5 minutes in the hardening bath and washed the
paper for about ten minutes afterward since I've read that related alum
hardening baths may increase the acidity of the paper and diminish the
archivalness of the paper substrate as a result. Does anyone know if
washing will remove any harmful residuals in the paper? Has anyone else
used a similar chemical with good results?

Thanks for any info.

Joe
Received on Thu Nov 4 15:51:48 2004