U of S | Mailing List Archive | alt-photo-process-l | RE: Hardening With Glyoxal: One Shot?

RE: Hardening With Glyoxal: One Shot?

Fridge: I compulsively clean my utensils / vessels ect. The refrigerator
was set to 4C. Yes, I had heated the solution to approx. 50C / 20 mins.
(I always keep the gelatine solution over a coffe cup heater.)

Glop: I see... I use 20g sugar per 1000ml gelatine solution. Agree that
some pigments would indeed kill and/or inhibit growth of bacteria but
probably there are many that won't harm them.

As always; it depends...


-----Original Message-----
From: Ryuji Suzuki [mailto:rs@silvergrain.org] 
Sent: Tuesday, May 08, 2007 11:03 AM
To: alt-photo-process-l@usask.ca
Subject: RE: Hardening With Glyoxal: One Shot?

> I once refrigerated 8% gelatine solution (plain, w/o any biocide +
> hardener) and reused it two weeks later w/o any problems.

Just plain 8% gelatin for two weeks? I'm not sure, but if you clean
everything thoroughly 2 weeks in good refrigeration may not completely
degrade gelatin, especially if you heated the solution and the storage
container hot enough to kill much of the bugs before storage. Unless the
bacterial activity is suppressed, I do expect that the average molecular
weight of the gelatin to be lower after 2 weeks than in the fresh

> More AFAIK, in
> carbon printing, it's a common practice to prepare the "glop" 
> (gelatine
> + sugar + pigment + optional: glycerol) beforehand and remelt it when
> necessary... How do you explain this fact?

Depending on how much sugar and pigment are put into the solution, they
may work as a mild bacteriostat.