U of S | Mailing List Archive | alt-photo-process-l | Re: haunted GUM (i surrender)

Re: haunted GUM (i surrender)

I printed on unhardened gelatin when I first started printing gum, and had no problem with it (I stopped when I learned by accident that the paper I was using printed beautifully unsized, and printed on unsized paper for years after that) and I know of a number of people who use unhardened gelatin with no problem. I have somewhere on my site a demonstration that shows that an unhardened gelatin size gets hardened in the gum printing process (the dichromate in the gum emulsion acts to harden both the gum and the gelatin) and if the image has areas of pure paper white, where the gum and gelatin aren't exposed and so the gelatin doesn't get hardened, you can get rid of that uhardened gelatin after printing (if you're concerned about the unhardened gelatin inviting bugs or fungus) by running warm water over the print. I can't think of the name of that page at the moment, and I have a feeling it's not linked into the index, but if anyone's interested I could look for it after a while.

On Oct 9, 2009, at 10:02 AM, Tomas Sobota wrote:

Ok, maybe you both are right and sized but unhardened paper works, I don't know. The fact that I was using paper intended for oilprints probably makes a difference: it had three very heavy coats of gelatin.
Also, using colder water might make a difference also. With warmer water some pigment will possibly get in the softened gelatin, which will be later hardened by the dichromate, with the pigment still in.

2009/10/9 phritz phantom <phritz-phantom@web.de>
i have printed on unhardened gelatin for about a year and a half. it was
when i first started printing gum and i didn't know where to buy any
hardening agents then and i also liked to have one poison-free step
where i could be a little more careless. and i got usable images too.
all my development baths are below 20°, as cold as it comes out of the
tap. i rarely raise the temperatur and only if i have a reason to. but
at the time i used to apply a coat of gelatin before each layer of gum
to avoid staining.
a feeling tells me it's neither paper nor size.i occasionally got
non-clearing layers before, but never that consistent. always a one time
thing and a new emulsion and a new sheet of paper eliminated it. i
always blamed it on bad pigment handling, brushing the emulsion too deep
into the fibers and/or a bad phase of the moon.
on the other hand all my other hunches were completely wrong (the
dichromate, the gum...). so i will have to look into it.

i my experience the gum process tolerates a lot of abuse, but if there's
a certain (unknown) tiny thing wrong, which it doesn't like, it ceases
cooperation completely.
for now gum and me are not on speaking terms!


geoff chaplin schrieb:
> I experimented with using non-hardened gelatin and found no difference
> in the final print -- I made a total of about 20 prints on unhardened
> sized paper. I developed in cold water (20deg or under). The only
> problem was the unhardened sized paper was slightly slippery to handle
> and presumably is susceptible to fungal attack if it gets wet. Other
> than that I could find no difference.
> Geoff Chaplin
> ジェフ チャップリン
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