From: Joe Smigiel (jsmigiel@kvcc.edu)
Date: 09/27/03-07:38:22 PM Z
Sandy,
The test will give relative information but is essentialy useless, IMO &
IME, for determining actual/absolute degrees of staining unless you add
dichromate solution to the pigmented gum in the ratio you will actually
use to print. Performing the test as it is stated in Crawford (and
elsewhere) could help you determine that pigment A may stain more than
pigment B, but it won't tell you that the threshold of staining for
pigment A is X grams per Y ml gum for gum printing. The addition of
dichromate sensitizing solution thins the emulsion and extends the
setting time. I believe this reduction in viscosity allows the pigment
to penetrate the sizing and stain the paper. So, IMO, to properly
determine the staining potential you need to add sensitizer to the mix.
You'll get staining by using thin solutions, not by loading the mix with
too much pigment. (Too much pigment prevents proper exposure and causes
flaking of the emulsion.) I have a copy of a stain test I ran with some
Daniel Smith tube watercolors around somewhere. I'll try find it and
scan it next week at work if you wish to see it.
Joe
>>> sanking@clemson.edu 09/27/03 12:22 AM >>>
Dear list members,
After seeing some of the beautiful results t hat are being had with
gum-over methods (gum-over pt/pd, gum-over kallitype, gum-over
cyanotype, etc.) I have recently been considering doing some gum
printing again after a long period of abstinence.
So here is the thing. In doing some research on gu m printing I
happened to come across a section in William Crawford's article on
gum printing in Keepers of Light called Pigment Concentration.
Crawford's description of the dot test method to determine the right
pigment-to-gum ratio for various colors and papers surfaces sure
seems interesting. I wonder if anybody on the list has actually tried
it, and if so, what are there thoughts about how well it works?
Thanks in advance for any useful information or opinions you may have
about the dot test me thod described by Crawford.
And BTW, please don't refer me to the list archives. Even though the
test may have been discussed on the list at some point in the past I
would really like to hear some fresh opinions on the subject.
Sandy King*
This archive was generated by hypermail 2.1.5 : 10/01/03-03:09:00 PM Z CST