Re: Autoclaving gum and gelatin

Date: 02/08/05-01:03:29 PM Z
Message-id: <>

I've lost track...what's the original question/issu?

In a message dated 2/8/05 4:31:49 AM, writes:

> On Sun, 6 Feb 2005, Sandy King wrote:
> > As for the change of state, what I refer to is the ability of gelatin to
> > absorb water and swell, and when heated, reach a melting point and form a
> > colloid, then to set again when allowed to cool. So long as a gelatin
> > solution is capable of changing between these two states it should be good
> > for both gum bichromate and carbon use, IMHO. If the gelatin looses its
> "Should !"  That's like "probably" or "arguably" and the other empty
> calories that infest the canon.
> Not to mention that you are in error anyway (and I break my promise not to
> continue this thread, as, from the kindness of my heart I give you info
> you clearly lack). That's error BESIDES the "seems-logical disease," in
> which you extrapolate from theory (I suspect of your own
> choosing/devising) rather than observation.
> There is also the fact that I have taken gelled gelatin out of the
> refrigerator, that is, gelatin in a state of gel that was, alas, rotten
> (as could be told from its stink, not its "state"), and, refusing to bow
> to the evidence of my nose, coated a paper with it.  The print failed
> miserably.  Not expecting to be called to the witness stand, I made no
> record of details, except that I threw out both the gelatin and the failed
> print (not knowing at the time what I learned subsequently, that a new
> layer of "good" gelatin would probably rescue it -- another item I learned
> from students).
> I cordially invite you, however, to repeat the "experiment" yourself --
> about a week in a refrigerator as funky as ours should suffice.
> While you're at it, you can try hosing a developing gum print with
> scalding water and note time, temperature, pressure and results with, say,
> 3 different emulsions and exposures. You should also enact the business
> about the boiling or the overheating you've been speaking of -- and see
> the effects for yourself.
> You could add to the sum total of human knowledge and/or learn that
> behavior of a gum print vis-a-vis gelatin is goosier than that of
> carbon... Of course the usual variables (paper, gelatin, hardener, water,
> rH, etc.) would affect outcome & should be controlled for.
> > ability to set, either from very extreme temperatures, being held at a
> high
> > temperature for a long time, or from repeated cycles of heating and
> cooling,
> > it will lose its ability to set. This will make it useless for both carbon
> > and gum bichromate.
> Again, with theory not firmly connected to the problem, let alone direct
> observation, you are in Assertion City. A gel that would no longer "set"
> could still coat a paper and dry enough in the air to be printed upon,
> though if it were applied directly from boiling, with no attempt to let it
> gel -- who's to know?  That is, gelling or not gelling enters the
> calculation only if you're testing for it.
> But go ahead, be my guest...test. Of course a proper test, controlling for
> variables of gelatin, temperature, degree and frequency of heating, etc.,
> could send students (ipods and all) into deep sleep.
> I prefer to simply warn them (and others) about heating the gelatin above
> 140 F. Something along the lines of my earlier exegesis Ryuji so kindly
> posted today. I have found that, barring inattention and hexed hot & cold
> water lines, it generally does the trick.
> Judy

Mark Nelson
Purchase the eBook & System for Your Own Custom Workflow@
Precision Digital Negatives
PDN's Own 31-Step Tablet Now Available—produced by Stouffer Industries
Credit Card & Paypal now accepted
Workshop info on Home Page
Received on Tue Feb 8 13:03:56 2005

This archive was generated by hypermail 2.1.8 : 03/01/05-02:06:54 PM Z CST