I have been working with gums a while and found success can only be
duplicated when a few controls are in place. Note that I am not doing
manipulation of the emulsion and my prints are typically "straight" and
always masked.
*I always preshrink the paper. I always size the paper three times. I don't
use formaldehyde since I started growing these extra ears and fingers...;-)
I use chrome alum as a hardener with the gelatin in one solution. I always
use surgeon's gloves and use a good exhaust fan at all times. The paper I
use is Rives BFK and the multiple layers of size does not eliminate it's
tooth. I haven't had any dichromate staining or difficulty in registration
in years. That makes the extra effort worthwhile.
*I tested every Winsor and Newton tubed watercolor pigment (available in the
U.S.) for staining on this sized paper. An accurate gram scale has no equal
here. Gum arabic is measured with a plastic syringe as is the dichromate
solution. A clear glass mortar and pestal (yes I have an address for them;
took me 10 years to find) is used over a light box when blending the pigment
into the gum arabic to ensure the color is suspended. The test did not
employ the use of any dichromate. Those pigments which did stain at weights
lower than .20 are not used. (I hope to find a painter to sell them to...as
there are many)
*Once I determined which pigments were applicable to the process I determined
the maximum weight of each in fractions of, or in, grams. Everything is
reasonably repeatable with the exception of humidity factors. Each color has
wildly different results.
*I use a saturated solution of ammonium dichromate mixed 1:1 with the
gum/pigment.
*My light source is 8 24" BL bulbs set side to side.
*I develop in 4 floating baths of 800 water; 15 minutes each; and hang to
dry.
*I am in the process of determining the greatest shadow each pigment can
produce using a Stouffer 21 step wedge. My intent is to find the exposure
for each pigment that sets the highlights while keeping the greys clear and
soluable.
Has anyone done similar testing? I have little information regarding light
sources and distance of prints to the source. I am beginning to test Winsor
and Newton gouaches to explore the possibility of setting highlights; only as
the first emulsion followed by watercolor. Has anyone tested this?
I welcome your own data and responses.
Carole Hollander
Gumprint@aol.com