From: Sandy King (sanking@clemson.edu)
Date: 12/04/01-01:53:18 AM Z
Judy Seigel wrote:
>
>However printers of yore added chrome alum to their gelatin, I forget the
>amount but surely in the "literature" or someone on the list will have it.
>I've always meant to try it, but somehow -- I feel more comfortable
>separating the two.
>
>Judy
Except for a short period of time when I tried glyoxal I have always
prepared the final supports for my carbon prints with chrome alum for
single transfer and potassium alum for double transfer, mixing the
gelatin with the alum solutions before applying to the paper. Chrome
alum is a much more effective hardener and is needed for the hot
water development of single transfer, whereas potassium alum leaves
the paper with a relatively soft layer of gelatin which will still
swell considerably, needed to receive an image from plastic as in
double transfer.
There is in my opinion no reason chrome alum (potassium chromium
sulphate) would not work for gum printing. You need only about 2g per
1000ml of gelatin solution. I would recommend first mixing the 2g of
chrome alum in about 100-150 ml of warm water, and then add to the
gelatin solution.
With chrome alum you avoid the very obnoxious and dangers odors you
get with formalin but exercise care in using it because it about as
toxic as the dichromates, ie, moderately toxic by skin contact and
highly toxic by inhalation.
Sandy King
--
This archive was generated by hypermail 2b30 : 01/02/02-04:47:33 PM Z CST