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

Re: Hardening With Glyoxal: One Shot?

I was just thinking "whither Ryuji?"....So are you advocating using both a
biocide and a hardener with gelatin? If the hardener's not a biocide are
people fooling themselves? Should we separate biocides and hardeners into
separate categories? My stock gum arabic I assume has a biocide already in
it. I understand the purpose of the biocide but has the term "harden" been
applied too loosely in the past? Hardening without a biocide presumably
still leave the gelatin open to attack.
 For my own purposes I'd like a method of being able to size small amounts
of paper. So ideally a stock solution of gelatin that can be rewarmed and
then I'll add in drops of my hardener of choice, that sound about right?
Thanks Ryuji!

----- Original Message ----- 
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@usask.ca>
Sent: Monday, May 07, 2007 1:32 PM
Subject: 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.