Re: Gum and Solutions

<Sandy said>I looked at Sam Wang's
> formula and unless I am reading it wrong he appears to be using about
> a 3% dichromate solution, which seems much weaker than what most
> other folks seem to use.

Sandy,
     You're right in that the amount of dichromate per 10cc of
gum/pigment/water (10cc) is .3 grams or 3% technically in Sam's formula, but
since gum printers use a premixed dichromated water solution (not dry),
usually let's say 1:1 with the gum/pigment, Sam's .3 grams would actually be
similar to using a 6% premixed ammonium dichromate solution mixed 1:1 with
the gum/pigment. When I use my "30% " saturated am di solution mixed 1:1
with gum/pigment, I end up with 1.5 grams of am di per 10cc of
gum/pigment/dichromate mixture, 5x as much as Sam's.
>
> What you can tell from the above that speed increases quickly as the
> strength of the dichromate sensitizer is increased from 1/8% to 1/2%,
> but above 1/2% it stabilizes.
> Sandy

Thank you thank you thank you! This is EXACTLY what I felt might be the
case! I just *knew* you'd know this...
Chris
Received on Sun Nov 23 16:49:54 2003