Re: Gum consistency and preservatives.
Gayster Alain (agayster@club-internet.fr)
Wed, 18 Jun 1997 22:10:23 -0700
Art Chakalis wrote:
>
> On Tue, 17 Jun 1997, Judy Seigel wrote:
> >
> >
> > On Tue, 17 Jun 1997, Art Chakalis wrote:
> > > I use thymol in place of mercuric chloride. However, if you mix your own
> > > gum solution you also need to keep it heated for a period of time to
> > > destroy any enzymes that are found naturally in gum. However, too
> > > much heat will degrade the gum itself. I typically heat to 140 F for
> > > about 1/2 hour to deactivate the enzymes.
> >
> > Art, I happened to be in TALAS today, which has conveniently moved next
> > door to my storied gym, buying various goodies (including TA DA! the
> > Dahlia mister!!!) and asked about heating the gum arabic. Experts there
> > had never heard of it, nor have I come across a mention of same in 97
> > years of the "literature" on gum printing. I was advised to ask you, sir,
> > for your references!!!
> >
> > In any event, I'm curious what the enzymes are supposed to do or not do.
>
> Judy, Remember that I work in the food industry . . . guess who uses the
> majority of the gum arabic (you've got one guess). Generically I sourced
> several food scientists. Specifically, look up the following books which
> I believe will bear out similar concepts (the 1st book calls out oxidases
> and peroxidases which are believe are currently believed to be enzymes.
> Also, the heat treatment I give is less than you'll find in either
> reference, food scientist's recommendation to keep the heat degradation
> minimized for my photographic applications.
> Well, may be. Remember the work of Louis Pasteur. He was the first to tell there is no
spontaneous generation. But in his experimental work, he used a very peculiar bottle,
swann neck he named it. He put some cotton in the neck to avoid living bacteria to come
in. And he demonstrated that there is really no spontaneous generation (the liquid
stayed clear). But he never opened the bottled. We have to open it to get the gum to
work with it. So the bacterias go in when we do this. The best is to put some
preservative in the gum, and to take it in refrigerator. Cold slows any chemical, or
living reaction.
> "The Water-Soluble Gums" by C.L. Mantell, Ph.D.
> Reinhold Publishing, 1947 (this one pre-dates ISBN numbers)
>
> "Handbook of water-soluble gums and resins" McGraw Hill, 1980
> ISBN 0-07-015471-6
>
> > I've also parted with money recently in exchange for 100 grams of thymol
> > in crystal form. Can you tell me what % solution to mix and how much you
> > add to the gum solution?
>
> I use .25%, your 100 grams will last you quite a while.
>
> AND . . . I think you'll find both books very informative as to why you
> get the variability that you've observed. I'm not really certain what you
> can do about it though. Oh one other thought, look up Gum in your phone
> book, some of the larger importers are in your neck of the woods and may
> be willing to give you some other recommended reading.
>
> I hope this helps, Sincerely, Art
>
> Art Chakalis
> Columbus, Ohio, USA
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Alain GAYSTER à Paris (France) agayster@club-internet.fr
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