Re: formula needed: Gum Arabic from powder

From: Judy Seigel <jseigel@panix.com>
Subject: Re: formula needed: Gum Arabic from powder
Date: Wed, 24 Nov 2004 01:52:10 -0500 (EST)

> I used to put one drop of 37% formaldehyde in a 2-ounce bottle of gum
> arabic from powder -- and it kept indefinitely.

> Whether glyoxal or even glutaraldyhyde would work similarly, quien sabe?

I'm doubtful if this would work. When these chemicals are used as a
sterilizing agent, soil must be washed off first or the effect would
be diminished, because these molecules tend to bind with other stuff
available and therefore they aren't free when bacteria try to grow.

> I think that 15% thymol solution has also been used... (tho maybe
> that was just for gelatin...?)

Phenol, thymol, methyl p-hydroxy-benzoate, p-chloro-m-cresol,
pentachlorophenol, 2-phenylphenol, etc. are all good. Sodium salt of
2-phenylphenol is probably most effective and easiest to buy. Bayer
sells it under "Preventol ON extra flakes" and Kremer Pigmente sells
this same stuff under the same name, but only in small quantity in a
small plastic bag.

I use it in quantity about 1/300 of the gelatin content. My emulsion
is free of bacterial attack or mold growth after a couple of month,
without affecting speed, contrast or fog level.

--
Ryuji Suzuki
"People seldom do what they believe in.  They do what is convenient,
then repent." (Bob Dylan, Brownsville Girl, 1986)