Re: Glyoxal?

Ryuji,

it's exactly what I did before asking this question though I admit because I
didn't find what I was looking for doesn't mean it's not there. I found that
some product, which use glut as one of the component, with other chemicals
to bring the PH high as you said below, would work well as both hardener and
preservative but I just wanted to compare glut by itself with formalin on
the preservative side.

Regards
Yves

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: "alt-photo list" <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, January 14, 2006 6:25 AM
Subject: Re: Glyoxal?

> I wouldn't count on it. Glutaraldehyde is an excellent sterilizing agent
> but at this low concentration and rapid reaction with gelatin, I don't
> think there's enough excess to act as a sterilizing agent.
>
> Usually, glut is used for sterilization purpose at pH of 8 or 8.5, and
> at a concentration of 2 to 5%.
>
> Of course, a lot weaker strength may be sufficient for bacteriostat
> function. BUT for that goal I would recommend using 2-phenylphenol,
> p-chloro-m-cresol, thymol, etc. rather than aldehydes.
>
> All these things are discussed in depth multiple times, so you should be
> able to find the info by searching the archive.
>
>
> On Sat, 14 Jan 2006 06:04:33 -0500, "Yves Gauvreau"
> <gauvreau-yves@sympatico.ca> said:
> > Ryuji,
> >
> > that's great, thanks Ryuji. I read somewhere that formalin was both a
> > "hardener" and a preservative, do you know if it's the same with
> > glutaraldyhyde???
> >
> > Thanks again
> > Yves
> >
> >
> >
> > ----- Original Message -----
> > From: "Ryuji Suzuki" <rs@silvergrain.org>
> > To: <alt-photo-process-l@sask.usask.ca>
> > Sent: Saturday, January 14, 2006 4:44 AM
> > Subject: Re: Glyoxal?
> >
> >
> > > From: Yves Gauvreau <gauvreau-yves@sympatico.ca>
> > > Subject: Re: Glyoxal?
> > > Date: Fri, 13 Jan 2006 23:14:40 -0500
> > >
> > > > I'm not sure I understand which one to use with the recipe you give
in
> > the
> > > > first paragraph. I'm surprised with all this, only 0.15 gram of the
> > stuff
> > > > for a liter of gelatine, it doesn't seem like much. I suppose as
long as
> > it
> > > > does the job
> > >
> > > That amount is sufficient if you use glutaraldehyde. The amount of
> > > hardener molecule needed to crosslink a sufficient fraction of gelatin
> > > macromolecule, 0.5% weight of hardener is still more than enough. The
> > > reason formaldehyde and glyoxal are used in much larger quantity is
> > > that those agents are far slower in crosslinking reaction, and much of
> > > them would evaporate, oxidize, or somehow involved in other reactions
> > > to leave the reaction system before they get to harden gelatin. In my
> > > view glut is far better agent to use because (1) very small excess
> > > agent is needed, so there's little need to worry about large excess
> > > causing trouble later, as with the case with glyoxal; (2) hardening
> > > reaction is fast and stable; (3) crosslinking reaction is
> > > nonreversible, unlike formaldehyde; (4) glut doesn't fog silver
> > > gelatin emulsion, unlike formaldehyde.
> > >
> > > Glutaraldehyde is an excellent gelatin crosslinking agent. It was once
> > > as a standard hardening agent in photographic industry. It was also
> > > used in older color reversal processing sequence as an emulsion
> > > hardener. The industry replaced it with an even faster reacting
> > > hardeners, but those agents are toxic and they also harden gelatin
> > > almost instantly, and so they aren't suitable to hand coating of size
> > > or silver gelatin emulsion.
> >
Received on Sat Jan 14 06:31:32 2006