Re: Water and gum coating

<Katharine Thayer asked> It would be interesting to know whether people
have
seen these huge
> differences in practice. I can't check it out because my humidity is
> high year round. But this makes me wonder about something else. I may
> have the timing wrong, but wasn't it about the time you moved from
> Montana to the South, Chris, that you started working with diluted
> dichromate and were surprised to find that you could print with very
> short exposure times, not that different from what you were experiencing
> before with saturated dichromate? If so, it may be that the increased
> speed of the damper coating offset the decreased speed of the dilute
> dichromate, and that's why you weren't seeing a big difference in the
> speed. Just a thought.

Christina wrote:

     Not exactly...I started gum printing in SC with saturated right
away,
and didn't switch to the lower dilution until the end of last year,
actually
right around the time the humidity got closer to the 30% mark instead of
the
60% mark (indoors, considering I have a heat/air conditioning unit
there).
     However, I was already printing in high humidity in MN over the
whole
summer, with the saturated am di.

_____________________________________________________________________

KT: Well, it was a great theory, so much for that theory.
_____________________________________________________________________

Christina:

The other intriguing thing, though, from Demachy's account, that
somewhere might fit into some of the stuff you are investigating, is an
infrequent occurence he had where a gum layer was fine and stable, and
for
some reason all of a sudden it solubilized. I can't locate the book at
the
moment--still packed--but it is at the end of the book if I remember
correctly where he explains the previous saturation of paper with
dichromate. That there may be a reason that hardened colloid can become
unhardened and why this sometimes happens is very interesting. It has
not
happened to me, tho.
_____________________________________________________________________

KT: Chris, I hope you can find this once you get unpacked, because this
mention is the first thing I've ever heard that would suggest that this
has been seen in gum. It's definitely not in that last section, and I
don't see it on a quick flip through the rest of the article. No doubt
you will be able to find it faster; it's always easier to recognize
something you've seen before than find something for the first time
Katharine.
Received on Wed May 19 08:38:11 2004