Re: Dichromate/ size/tricolor/pigment

Albert Strauss (a.strauss@worldnet.att.net)
Mon, 22 Jul 1996 12:36:54 +0000

At 03:31 AM 7/22/96 +0000, Larry Shapiro wrote
>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,

Thanx for your efforts and the information. It would be very helpful to
those like myself and other list folk if you (and other experimenters) could
be more specific about your test parameters so that we can repeat these
tests on using the same or other
materials for comparison. As you so rightly point out "small differences in
materials or process can make for a significant difference..."

I would like to know:

What sensitizer, ratio of sensitizer to gum?
What paper, what size, what hardener, how applied ?

Peace
Al