From: Judy Seigel (jseigel@panix.com)
Date: 09/29/03-02:05:36 PM Z
On Sat, 27 Sep 2003, Joe Smigiel wrote:
> 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 ...
> 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.
I nearly always dilute my emulsion with extra water because it's so much
easier to coat... your point that it extends the setting time is
succinctly put & IME crucial.... Yet I haven't found that it increases
staining. Maybe that's degree of dilution? Or of the particular gum or
size?
But I meant also to mention to Sandy that for gum-over, it needs testing
over the undercoat, which would anyway be a whole other thing, or so I
would suppose.
J.
(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*
>
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