Re: Autoclaving gum and gelatin

Judy wrote:

>
>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.

Sure it did not work, because by the time gelatin
starts to rot it has already lost much of its
ability to change states. You might have noticed
that while in the refrigerator it was beginning
to run as it rotted. Had you melted it completely
at that point you would have found that it would
not set again. So this reasoning on your part
clearly fails the smell test.

>
>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 appear to have confused me with some other
person. The only assertion I have made as to
temperature is that gelatin will not break down
at 140 º F. At no point have I spoken of boiling
gelatin or developing it in scalding water. All I
have affirmed is that gelatin will not break down
at 140º F if held at that temperature for only a
relatively short period of time.

>
>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.

If any testing needs to be done to prove
anything, you are the one who needs to do it
because it is your assertion i.e. that gelatin
will break down if heated to 14oº F, that is out
of touch with both the experience of others as
seen in the thread, as well as theory. Since you
appear to be the odd man out I would hope that
you would at least be gracious enough to
entertain the possibility that it is you who are
wrong, not everyone else.

>
>
>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.

If warming the gelatin solution to a moderate
temperature works for you, so much the better. I
have at no point suggested that one *must* heat
the gelatin to over 140º F for it to work in gum
printing, only that heating it to that
temperature will not do it any harm.

Sandy
Received on Tue Feb 8 10:39:55 2005