Re: Hardening With Glyoxal: One Shot?
Gelatin solution does not keep very well even if refrigerated, unless a small amount of biocide is added. A couple of days may be ok but bacteria grow very well on gelatin solution. They break down gelatin molecules to smaller molecules and their gelling property is affected. http://silvergrain.org/wiki/index.php?title=Biocides Compounds that hardens gelatin molecules should not be counted on because they bind with gelatin molecules and not available to kill bacteria. Ones that are photographically inert and don't react with gelatin should be added, if the sizing solution is to be kept for later reusing. Hardener is best added immediately prior to coating, as already discussed.