Re: humidity and gum coating
Dunking rather than soaking the paper, then hanging to drip, blotting
it, followed by coating may be a way to prevent the inner fibers from
Also, I found that if a foam brush is held in the steam spewing out of
a humidifier for ~10 sec, it was reasonably uniformly humidified prior
to using it for coating.
On 2-Sep-06, at 9:12 PM, Judy Seigel wrote:
On Sun, 3 Sep 2006, Tom Sobota wrote:
As to why some papers develop spots when coated wet, that's a good
question, I haven't the slighest idea. Differences in surface
porosity come to mind, but these papers have been double-coated with
gelatin and hardened ...
For the sake of "experiment," I tried coating the gum emulsion on
pre-wet paper a couple of times a while back, and found some spotting,
but mostly staining. Serious staining. I theorize that even though
the surface was blotted off, the interior remained wet and that the
emulsion soaked down & settled in there -- in other words, got tangled
into the paper fibers, as it doesn't when it just sits on the
I gather the reason for coating wet in the 1st place is to get an even
coat. IME, coating with a fairly wide foam applicator (the kind with
the wood handle that has been very slightly dampened & then blotted
dry) and NOT NOT NOT hake brush, spreading swiftly and THEN smoothing
with dry hake, solves any problem with coating.
It's important however to move across the surface quickly, meaning in
wide free strokes. Trying to "smooth" as you go (instead of later)
slows you down, and (I find) by the time you get across, it's started
to get tacky & stripe-y where one stroke passes the next. In other
words, the risk of streaks is with the initial dispersal. Once that's
done, you can "buff" at relative leisure.
However, this works best with a relatively thin emulsion, at the very
least equal parts am di solution & gum...