Re: archivalness of gum
From: Dave S <fotodave@dsoemarko.us> Subject: RE: archivalness of gum Date: Fri, 21 Dec 2007 11:04:09 -0500 > Ok, mybe in a less technical sense, does hardening reduce or > minimize the problem with bugs? No. > I have always thought (though I have no scientific proof and > didn't check) that the hardened gelatin would capture less > water from the atmosphere and so would preserve > better... sort of like a jello would certainly spoil faster > than the dry gelatin powder. Is this not true? Hardener only suppresses swelling of gelatin when the gelatin is soaking wet or half wet. Once dried, the ability of gelatin to exchange moisture with air is mostly determined by the air temperature, humidity and the plasticizers used in the gelatin coating, if any. Hardener has little or no influence on this. Also, hardener molecules are tightly bound to the host macromolecules and not really free to act as biocide as you would expect from free aldehydes. If you want to protect gelatin from fungi you should use suitable humidity control. A RH of 30% is very good. Another approach may be to use a fungicide treatment of the image. I was asked by several people to offer such a product (Tetenal made a final rinse solution containing a biocide, for example) but I was reluctant to do so. Fungicide may prevent fungus but high humidity is not a desirable condition for the image permanence even if fungus problem does not occur. Humidity control, while potentially expensive depending on the region, is the best overall solution. -- Ryuji Suzuki "Patriotism is the last refuge to which a scoundrel clings." (Bob Dylan, Sweetheart Like You, 1983)
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