Sil Horwitz (silh@iag.net)
Wed, 17 Mar 1999 15:25:04 -0500
At 99/03/17 11:15 AM -0800, Adam wrote:
>It seems that with Argyrotypes, it is all in the paper and the tween. But,
>tween gets moldy as many of us have noted. I don't know how/if the mold is
>affecting my prints, but I need some fresh stuff to try it out. So, in the
>interest in saving some money, I wonder...
>
>Sigma lists: Polyoxethylenesorbitan (aka Tween) - Monoaurate (Tween 20) -
>100 ML for $16.30 - however, they don't provide the percent solution. Since
>they don't list it, I am wondering if this is 100%? Could I buy this, and
>dilute down with water? If so, would this solution have fewer problems with
>mold?
As I have mentioned before, Tween is not the ideal wetting agent for
photographic solutions. Kodak uses now, and I have almost always used, one of
the PEGs - you will note this compound is often used in food products. PEG is
the acronym for polyethylene glycol, which is available in many numbers which
correspond to the molecular weight. They are almost all interchangeable, but
you must change the necessary amount corresponding to the density. I use PEG
4000, because it is a fine powder that dissolves readily, and does not
deteriorate in the powder form. It is sometimes available commercially as
Carbowax, but usually in one of the lower polymers which are wax-like and take
longer to dissolve. Tween is a sorbitol derivative; since sorbitol is a sugar,
Tween is subject to bacterial and fungal action. PEG, in my tests, has proven
to be inactive in photographic solutions, which is why I use it as my preferred
wetting agent. Commercially, it is inexpensive; from the scientific supply
houses, like most of their chemicals, you pay for the packaging. In my most
recent formulations, I add 0.5 g (1/2 gram) per liter of working solution. (I
even use it in fixer, as it speeds the fixing process.) You may need to
experiment a little for your particular application, but too much will produce
suds.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net
Visit http://www.psa-photo.org/
Personal page: http://www.iag.net/~silh/
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