Re: Autoclaving gum and gelatin and speckling

From: Christina Z. Anderson ^lt;zphoto@bellsouth.net>
Date: 02/06/05-08:47:40 AM Z
Message-id: <003e01c50c5a$d0e0a3a0$6101a8c0@your6bvpxyztoq>

Hi all,
I've read in the literature the 140 figure, and was always curious as to why
that temp.

I routinely heat gelatin for sizing and by the time I get around to
measuring it, it is usually 160-185. Then overwhelming guilt comes over me.

So if it is no problem, one other gum myth down the drain.

As for speckling, my **theory** is this: perhaps two causes, one being
sizing is not deep enough to catch the little fibers that stick up past the
sizing layer and the last layer stains, or two, the glyoxal has crystallized
the gelatin into a scratchy layer on the surface of the paper and it catches
and stains.

 In fact, there are several of us that have found that staining is worse on
glyoxal sized paper than unsized. The only way I can figure that out for
sure (for me) is if I go back and glut size Rives and see if there is no
speckling. I did not get speckling with formaldehyde sized Rives.

(I don't have a glyoxal vendetta, you all....I feel like I continually bad
mouth it, and I don't mean to, but it has its share of concerns for me.
Heck, glut does, too, I'm sure, and we'll find that out if a bunch of people
start using the Maco stuff. Maybe it turns black in 5.7 yr.)
Chris
(PS HEY NOT FAIR: I've gotten **hammered** for sharing stuff "in the
literature" as proof of something; consequently I've quit posting my old lit
findings. So Judy, if you use that as support for the gelatin controversy,
I can, too! Demachy here we come...)
(PPS If Jello starts with boiling water, it says, and then cools why don't
we do this with our gelatin size??)

From: "Sandy King" <sanking@clemson.edu>
The plain fact of
the matter is that gelatin can be heated to a
much higher temperature than 140 F and still
retain its setting properties. In mixing gelatin
solutions for making carbon tissue some of us are
heating the gelatin to close to 200 F, for a
short period of time, without experiencing any
problems with setting properties
Granted, there must be some temperature so hot
that it will break down the gelatin within a
short period of time, but 140 F is not even a
ballpark figure for that happening.
Sandy

>>>Gelatin raised above about 140 F is useless for sizing purposes if that's
>>>what you have in mind -- it breaks down. >>>Judy
Received on Sun Feb 6 08:47:54 2005

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