Re: Sizing with unhardened gelatin

Katharine,

How strong a gelatin coating did use for your unhardened sizing? I tried
this once a few months ago and the gelatin softened enough when brushing on
the gum that it mixed into the brushstrokes and didn't keep its integrity as
a size. Did you brush on the gelatin?

Jack

> From: Katharine Thayer <kthayer@pacifier.com>
> 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.
>
> http://www.pacifier.com/~kthayer/html/Current2.html
>
> 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 16:30:11 2004