Sizing with unhardened gelatin

From: Katharine Thayer ^lt;[email protected]>
Date: 05/04/04-07:56:10 AM Z
Message-id: <>

Helloa All,

Probably few will be interested in this as I daresay most people who use
gelatin size just harden their size as a rule, but here goes.....

A few weeks ago there was a discussion about whether gelatin size for
gum needs to be hardened or not. I said that it seemed to me that where
there is tone, the gelatin will be hardened in the gum printing process,
and where there isn't, the unhardened gelatin could be easily removed by
pouring boiling water over it. Since I know for a fact that I can pour
boiling water over my gum prints without fazing them, and since we know
that gelatin can be hardened by a dichromated colloid process, these
suppositions seemed reasonable to me.

Curiosity finally got the best of me and I demonstrated this to myself
empirically: at least with my gum prints, it works quite well-- the
gelatin hardens where there is exposure, and is easily removed with hot
water (after the finished gum print is dry) where there isn't exposure.
I could have used boiling water; it wouldn't have hurt the gum print,
but I found that hot water out of the tap works just as well. I used
pigmented gelatin so the presence or absence of the gelatin could easily
be seen. Unfortunately I didn't think to scan the test prints while they
still had the colored gelatin on them so YOU could see the difference as
well as I could, but for whatever it's worth, I did see it with my own
eyes and am satisfied that this works quite well, with the caveat of
course that the gum must be properly hardened.

I prepared a quick webpage showing this; the visuals aren't great but I
hope the point comes across. I don't have time to redo the scans.

Katharine Thayer

Katharine Thayer wrote:
> On reflection I find that I am not as persuaded by Judy's argument here
> as I thought I was. I was trying to be agreeable, but actually my
> suggestion isn't so tremendously theoretical. I know from experience
> that I can pour boiling water over my prints with no ill effect; I know
> from experience that I can soak my prints in boiling water with no ill
> effect, because I did both of these things recently to demonstrate the
> tenacity of properly hardened gum for my page in progress on the
> chemistry of the gum process. It's certainly reasonable, given the
> melting point of gelatin, to suppose that boiling water would melt any
> unhardened gelatin in the paper. So I don't think this is such a
> cockamame idea at all.
> I backed off because I realized that not all gum printers print in such
> a way as to actually harden their gum, and of course this wouldn't work
> on unhardened gum, which dissolves much more easily than unhardened
> gelatin. I personally don't understand why anyone would print in such as
> way as to not harden the gum well, given how ferociously soluble
> unhardened gum is, but as I always say, "each to his own."
> Katharine Thayer
> Judy Seigel wrote:
> Katharine Thayer wrote:
> >
> > >
> > > > ....If there are large areas of white in the
> > > > image, you should either harden the gelatin before printing, or soak the
> > > > print in hot water after printing to remove the areas of unhardened
> > > > gelatin that weren't hardened during printing due to lack of exposure.
> > >
> > > I would not advise that, at least not without careful testing... First,
> > > to get the water hot enough to melt off gelatin without any agitation --
> > > just melt it off the paper, especially when it may have had *some* tanning
> > > -- is not a sure thing. Secondly, that could well soften your image,
> > > which if you've used low dichromate and minimal exposure could be soft and
> > > susceptible, and melt some of that off as well. But the idea seems highly
> > > theoretical, at least until proved by testing (tho how you test to see
> > > that the gelatin is off I don't know). And even if it "worked," sounds
> > > like more trouble than hardening.
> >
> > Here I have to agree with you; that was a half-baked idea that had no
> > basis in experience. I don't know what came over me; I don't usually
> > talk off my elbow like that. I guess I was just trying to think of a way
> > around hardening, because I'm kind of down on hardening at the moment
> > and wanted to give people an alternative. But I agree, it wasn't a
> > well-thought idea. I'm pretty sure it would work for my method, because
> > when I'm done my gum is well hardened; you can pour boiling water over
> > one of my finished gum prints (I tried it a couple of weeks ago for an
> > illustration for my website) without affecting it in the least. But I
> > am aware that not everyone prints the way I do.
> > Katharine
Received on Tue May 4 15:43:56 2004

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