From: Judy Seigel (jseigel@panix.com)
Date: 08/03/03-10:56:04 PM Z
On Sat, 2 Aug 2003, Christina Z. Anderson wrote:
> ...I
> understand the issue quite well, and both sides of the issue quite well.
> One side says staining is in direct relation to pigment to gum, even whether
> dichromate solution is present or absent from the mix (not exposed). You
> say
> staining is not related to the pigment to gum ratio, in fact, "increasing
> pigment has NEVER resulted in staining, staining DID occur when the emulsion
> became thin as a result of adding more sensitizer or water" (viscosity
> factor), but, in fact,
Chris, is that supposed to be a direct quote from me? Doesn't sound like
my words unless out of context... I doubt I'd say "never" anyway because
I've always pointed out that if you increase the pigment odds are good for
more stain in an ABSOLUTE sense, even if not in a relative sense. I did do
tests where double pigment actually stained less -- but that wasn't a
heavily staining mix to begin with.
And I have pointed out REPEATEDLY that I use a quite thin emulsion, not
liking AT ALL the thick coats currently under discussion -- I find they
dry and get sticky before they're smoothly coated ESPECIALLY when working
large, and I also don't like the way a thick coat develops (whole wodges
will come off when you're trying to modify -- like snow falling off the
roof).
Which is not to say that the way Melvyn is using them can't work fine, but
as a general rule, plain old garden variety gum printing coats and
develops better FOR ME with a thinner coat - that is, about 2 parts liquid
to one part gum.
As for Anderson -- his principle was apparently that stain kicked in at a
HIGHER RATE with more pigment...And that below a certain threshold stain
stained at a lower rate... Or why bother with the whole rigmarole? After
all, you'd expect to get less stain with less pigment. What's the point
of a *test* for that?
And if you've sized properly & your gum is compatible it's all immaterial
anyway --it's not going to stain hardly at all.
J.
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