From: Katharine Thayer (kthayer@pacifier.com)
Date: 03/18/03-01:30:27 AM Z
Dave Rose wrote:
>
If we're going to have an intelligent discussion on
> staining, let's differentiate between quinacridone violet and burnt sienna.
> Put aside all other variables, the pigments themselves make a huge
> difference in the results achieved.
Agreed. And not only that but the brand makes a difference, for those of
us who use tube paints. First of all you have to know what pigment is
used in the paint, because sometimes the paint name is the same as the
pigment name, and sometimes it's not. But even when you're sure of the
pigment, the different brands of paint use substantially different
proportions of pigment to gum, so you need to add more gum to some
brands than to others to get exactly the same tone. So instructions that
say, for example, 6 grams of lamp black to 12 ml of gum, are useless
unless you know the brand of lamp black you're talking about. That's why
general directions for understanding how to judge the appropriate amount
of pigment are more useful than specific instructions giving the exact
grams to use.
(Referring back to Chris's post) Of course the staining pigments need
more gum to keep from staining; that's true by definition. But that's
different from saying that certain pigments should be avoided for gum
because they stain, as some people say. The trick is just to get the
right proportion of gum to pigment. Most of these pigments are so
intense that a small amount will give you a surprisingly dark tone.
>
> Your comments on relative humidity are especially interesting. For whatever
> reason (much lower humidity and/or higher PH water?), my gum exposures are
> noticeably longer here in Wyoming than those made in New Jersey - with all
> other variables being the same.
>
The winter of 1998-1999 was so wet in the northwest that I had to adjust
my printing times, and then adjust again in the summer when the rain
finally stopped. I also remember a time when Stephen Livick was
pronouncing somewhere that gum simply could not be properly printed at
any humidity but (I forget the exact number, let's say 58%). At the
time, I was making perfectly fine gum prints in a dank cellar that
actually had a stream running through it; I had to wear boots to work.
Stuff like this is where I get my disdain for absolutist pronouncements
about how gum works. I'm quite comfortable with the idea that changes in
humidity require changes in practice, but not with the idea that one can
only print properly in a particular humidity range.
Katharine Thayer
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