Re: gum printing, technical and looong

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From: Judy Seigel (jseigel@panix.com)
Date: 03/01/03-04:45:23 PM Z


On Fri, 28 Feb 2003 Ender100@aol.com wrote:
>
> Is it incorrect theory or otherwise thinly spun that diluting the mix too
> much with water allows for more staining by not allowing the pigment to
> remain suspended/coated with gum? Perhaps like the micro-encapsulation of

You know Mark, I think it is generally speaking, within normal values,
incorrect. In my experience, the much greater risk is that the coat is
too thick so it flakes off, and/or you can't get it even. In fact Chris is
quoting Maskell & Demachy who said way way back in 1898, "most failures in
coating are due to an exaggerated thickness."

And the funny thing is, though I know this VERY well, the shibboleth about
having enough gum is, or was, inhibiting for a long time. Didn't someone
say here recently (possibly Jack Brubaker) that if you don't make the gum
layer so thick you can control it in development much more easily? Exactly
.... If it's a layer like a carpet, the least touch makes it roll up.

> Epson pigment inks? It would seem then that adding dichromate powder
> without the water would avoid this—while at the same time having
> enough water in the mix to make the gunk spreadable.

Another reason only a boy genius like Sam Wang can get away with that is
we mortals cannot measure such tiny amounts of dichromate accurately, so
results will NOT be repeatable... unless he has some secret way of
measuring powder for one print by number of grain particles.

Plus, if WE (or anyway I) use a freshly mixed dichromate solution it
speckles. I've found it needs about an hour to "ripen." In fact one of
those moments that live in a teacher's hall of horrors -- the first gum
workshop I taught, all the first prints came out speckled. (Before then
I'd taught a regular class, where we mixed the dichromate at the end of
one session and didn't use it til the next.) I was ready to march up to
the tech office and tell them, emergency -- GET NEW DICHROMATE, when the
NEXT student, who'd been a bit slow on the draw, came in with HER print...
perfectly fine, as were all the others after that.

> ... However, I will try Sam's
> method, but to be on the safe side I have ordered a HAZMAT suit from Bostick
> & Sullivan.

And be sure to factor in the time to get INTO that HAZMAT suit, and then
out of it. I mix a year's dichromate solution in that length of time.

> .... My understanding of the earlier discussion though was that
> adding too much dichromate solution was also diluting the mix too much
> because of the additional water being added—thus possibly leading to more
> staining.

There are so many variables here it's hard to isolate them, but on a sized
paper in normal room temp/ humidity, not over exposing, not leaving the
print til tomorrow or any other bad thing, I've never found a connection
between thin coat (which I find infinitely more controllable) and
"staining" --- though whether you mean PIGMENT stain, or DICHROMATE stain,
I don't think is clear. Either way, my tests show that either or both is
a problem greatly exaggerated.... And if it should occur, almost always
cleared by a long soak. That is, sleep on it.

And when you look at some of the pictorialist masterpieces, also the
GORGEOUS Sudek carbros, for instance, where the top value is about a 50%
gray, you have to ask, what is this morbid fear of a little pigment stain
anyway ???

PS. Since the THEORY (Mike Ware's anyway) has it that the dichromate
migrates to the surface of the paper, I'd guess that it could do that no
matter how thick the coat, and if it doesn't do that you don't get a
print -- I mean while we're spinning THEORY .... !!!

cheers,

Judy


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