Re: sizing with glyoxal

Glyoxal is an interesting hardener. I, as Judy, use 15ml per liter for
use in an "afterbath". What I found in testing was a "bell curve". For
my materials, less or MORE glyoxal increased staining. Test that
yourself, I assume different gelatins will require different hardening
percentages. Glyoxal, as with formaldyhide (spelling?), takes a day or
two to "cure" (don't use the paper for a couple days after hardening).

On Sunday, February 15, 2004, at 10:59 PM, Judy Seigel wrote:

>
>
> On Sun, 15 Feb 2004, Christina Z. Anderson wrote:
>
>> However, one observation I'll have to corroborate the next time I
>> size: the
>> glyoxal gelatin solution seemed yellower today than last night.
>> Whether
>> this leads to any explanation of the yellowing controversy we have
>> discussed
>> here, who knows. It was kept at 140-120 degrees for 15 hrs and is
>> yellower.
>> Any suggestions, chemists and gum printers? When brushed on the
>> paper, the
>> yellowing in a thin coat of size is not apparent so no biggie. Plus
>> I'll be
>> using it right away so it won't sit in a drawer to get yellower...
>
>
> Of course I repeat myself, but my suggestion is to apply the hardener
> as
> a separate coat -- you save all kinds of variables that occur when
> it's in
> the gelatin, including the aging and hardening of the combo... (Of
> course
> on the other hand, who knows what interesting creatures you could grow
> in
> a gelatin culture kept at 120 degrees for a day or two...)
>
> I also suspect that you'd use less glyoxal, which is a lot more
> expensive
> than gelatin... That is, unless you're brush coating the gelatin
> too...?
>
> For a separate hardening bath, I use 15 ml glyoxal per litre of water
> (the
> same amount I used for formaldehyde)... the sheets can be hardened a
> few
> at a time so a shallow tray full is OK... I rinse the paper after
> hardening -- and do not see any yellowing.
>
> J.
>
>
--------------
Tom Ferguson
http://www.ferguson-photo-design.com
Received on Mon Feb 16 09:33:05 2004