Re: preserver for gum

From: "Christina Z. Anderson" <zphoto@bellsouth.net>
Subject: Re: preserver for gum
Date: Thu, 26 Feb 2004 20:07:57 -0500

> Preservative choices and amounts:
> Several drops of formaldehyde per oz. gum
>
> Several drops of 2% solution of methylparaben (2g in 100ml water)
>
> 0.25% solution of sodium benzoate (1g in 400ml water)
>
> Thymol in isopropyl alcohol (100% alcohol, 1g thymol to 1 cc of alcohol)
>
> Carbolic acid 1 drop per oz. gum
>
> etc. etc.

It seems that phenolic bactericides are popular for photographic
processes (in OLD silver gelatin literature plain phenol, thymol,
etc. also appear to be the choice) but modern favorite choice of
phenolic bactericide is 2-phenylphenol for its favorable efficacy and
toxicological profile. Sodium salt of 2-phenylphenol is more easily
soluble in water, and it's available inexpensively in flake form
(tetrahydrate) from Bayer Chemicals AG as "Preventol ON Extra." Some
other products in Preventol line are other forms of 2-phenylphenol,
such as concentrate solution.

http://www.protectedbybayer.com/mpp/global/applications/industrial_application/concrete_additives/

I use 2-phenylphenol at about 0.2% (w/v) of silver gelatin emulsion
and I think this is a good dose for gum arabic. For cellulose based
adhesives 0.1% seems sufficient.

A quick google search gave me this link:

http://www.kremer-pigmente.de/78740.htm

Kremer Cat #78740 is "Preventol ON Extra" (sodium salt of
2-phenylphenol)

Quick view of other bactericides:

- 4-tert-amylphenol, 4-tert-phenylphenol, 4-(2-methylbutyl)phenol,
etc. These are very effective against gram positive bacteria, and
often used in conjunction with 2-phenylphenol mentioned above. I am
yet to find these adjuncts necessary for my applications.

- Formaldehyde is a very good bactericide but is also irritant and
susceptible to polymerization. Glutaraldehyde is more commonly used as
disinfectant or sterilizing agent at pH of 8, but suffer the same
polymerization problem at this pH. (and at higher pH values it is not
a good bactericide)

- Quaternary ammonium compounds like benzalconium and benzethonium are
relatively nontoxic to mammals so they are widely used, but these
compounds are inactivated by dirt, soil, nitrate ions, some organic
compounds like soap, etc. and these are poor choices as preservative
additive in gum arabic. Also, quarts affect silver gelatin sensitizer
and developing process, often in useful ways, but still these won't be
good choices as bactericides.

--
Ryuji Suzuki
"Reality has always had too many heads." (Bob Dylan, Cold Irons Bound, 1997)