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)

Loris can speak for himself, but I have never seen a dark reaction in a mixed emulsion, and like Keith, I am skeptical. Dichromated colloids in solution behave very differently chemically from dichromated colloids coated into a film. Three or four years ago, when I was studying the chemistry of dichromated colloids in depth, I could have given the details from memory, but now I'd have to look it up, but if there's a "dark reaction" in dichromated gum solution, it's not anything like the dark reaction in coated paper. I've kept a mixed emulsion for as long as eight hours without any problem, printing from the same emulsion for a long day; that's the longest I can say from observation. This is in the same conditions (ambient humidity >85%) where a coated paper would become entirely insoluble from the dark reaction in less than four hours. I mix my emulsion in very shallow dishes; if I leave a mixed emulsion overnight, it just dries up in the dish.

On Oct 28, 2009, at 5:23 AM, Keith Gerling wrote:

"BTW, it's not a good idea to keep the coating solution (gum/pigment +
dichromate) for a day. You'll get "dark effect". Just mix enough for
immediate use."

Loris, have you actually observed "dark effect" in wet emulsion? I'm skeptical whether is actually exists.

On Fri, Oct 23, 2009 at 8:18 PM, Jeremy Moore <jeremydmoore@gmail.com> wrote:
Our own clay harmon worked out a great method for working with it that
requires only a single coat with no more palladium solution required
than the same size print on cot-320. you add 1/4 of the emulsion again
in distilled h2o (so 18 drops palladium and 18 drops of ferric for an
8x10 is extended with 9 drops of h2o), after coating let it sit for 60
seconds, blow dry it to bone dry, then let it sit for to come back up
to ambient humidity--or you could just use a humidifier at this point
the surface has a velvety depth that is just stunning.

On Fri, Oct 23, 2009 at 7:51 PM, Marek Matusz <marekmatusz@hotmail.com> wrote:
> Jeremy,
> I would have never thought to use that paper for palladium. It seems it
> would soak a lot of sensitizer. The print is a gem.
> Marek