U of S | Mailing List Archive | alt-photo-process-l | Re: My own PVA glue sizing experience (attn: marek + the gum woesagain

Re: My own PVA glue sizing experience (attn: marek + the gum woesagain)

My understanding is the "absolute humidity" is very important in gum
printing (and many other alternative processes).

Relative humidity (RH) percentage - as measured by ordinary
hygrometers - is not much useful alone to judge the water content of
air; you must also take temperature into account.

See this: http://www.tis-gdv.de/tis_e/misc/klima.htm

My workflow is to coat the paper, wait 5 minutes (to the point where
the emulsion becomes pretty tacky / almost dry, meanwhile I clean the
mixing vessel and brushes), then dry further with a hair dryer at low
setting (until it's dry to the touch), and finally humidify the paper
using an ultrasonic humidifier. The only part I have to be consistent
is the humidifying *ritual*. (Note the emphasis!) With this workflow,
my exposure times are constant and/or comparable all year round in
almost every possible indoor environment condition I may encounter
(given I'm using the same paper; different papers may hold different
amnt. of water - also, the emulsion formulations should be similar),
since there is always the same amnt. of moisture in the paper. I also
keep the paper isolated during exposure by placing an impermeable
plastic sheet under it; the felt in the contact printing frame's back
may draw or introduce moisture during exposure. (Something I learned
printing pop palladium.)

Hope this helps,

2009/10/23 phritz phantom <phritz-phantom@web.de>:
> ...
> regarding humidity,
> since you know a lot more about the subject than me,
> do you think a change in weather (from a normal, sunny autumn day, to a
> rainy day) could change the humidity within my apartment in a way that it
> affects the drying of the gum emulsion?
> iirc, you humidify your paper before coating and/ or printing?