> It has long been known that an alkaline solution of formaldehyde is the
> most effective gelatin hardener. I presume glyoxal works the same way. This
> should be fairly easy to test.
Is that last paragraph you, Luis? I did test it. See archive last August
or so. For sizing gum, seemed better than formaldehyde....
> As explained in my books, chrome alum made acidic, is also very effective.
> I wouldn't worry too much about the acidic aspect of this liquid hardener
> if the print is thoroughly washed before drying.
>
If you mean you think the reason I added the alkali to the gyloxal was
worry about acid it wasn't..... It was because
1. Paulchemprof told me that formaldehyde -- and thus presumably glyoxal
-- links can open again in long soaks, which my gum prints get. Added
alkali, he said, prevents this.
and
2.the glyoxal working solution left plain tended to clump up, ie become
unusable, after a day or two, leading to much throwing out of working
solution. With the alkali added, to pH about 8 and 3/4, it keeps.
Judy