Re: Dichromate/ size/tricolor/pigment
LESMD@aol.com
Sun, 21 Jul 1996 23:30:43 -0400
Gummists,
With all the recent discussion on the variety of gum arabic around I made a
simple test which had quite startling results. I obtained small bottles of
four different gum solutions. My standard lithographers gum, Daniel Smith
regular gum, Daniel Smith Premium gum and Winsor Newton Gum. The first three
are reputed to be all 14x Baume will the last has no Baume rating but others
have reported it to be 16x. Five gms of Rowneys Jet Black gouache was mixed
with 25 ccs of each of the gums. I used this pigment because I agree with
Judy's assessment that this is a very good pigment for a one coat gum print.
The same amount of sensitizer, type of paper (all sized and hardened the
same) and exposure were used for each print. An enlarged negative with a
density range of 0.9 was used along with a step tablet. The prints were
given extended development ( in fact it was over night) to avoid any
differences in the development process.
The "best" gum was the Daniel Smith Premium with the Winsor Newton and
lithographers gum tied for second. The DS gum not only separated the low
values better but also cleared the highlights. I think that the issue is not
that there is a best gum but rather that small differences in materials or
process can make for significant differences in image quality.
Larry Shapiro