Re: Glyoxal?

Yellowing of gelatin is one of the most frequently mentioned issue about
hardening of gelatin with glyoxal on this list. It seems to me that, in
order to get useful degree of hardening in a reasonable time span, you
would have to use a lot of glyoxal, and, unless you remove the excess
after the gelatin is hardened, the residue will later cause yellowing
problem. All these problems are instantly solved by using a weak
solution of glutaraldehyde.

Glyoxal exists in monomer, hydrated monomer, dimer, trimer, etc. in
aquaous solution. Even in 40% solution, these species are present.
Trimer is more commonly seen in more concentrated solutions as well as
crystal form. I think the preferred choice (in terms of shopping) should
be determined by safety, ease of use, etc.

Glyoxalic acid is a partially oxidized form of glyxoal, where one
aldehyde group is oxidized to carboxyl group. When both aldehydes are
oxidized, it's oxalic acid.

On Thu, 12 Jan 2006 01:34:10 -0500, "Yves Gauvreau"
<gauvreau-yves@sympatico.ca> said:
> Katharine, Ryuji and all
>
> yes it helps Katharine . The first item in my catalog as the same CAS
> number
> as you mention and your right again about the concentration it's 40%
> (38-42%) here also. The formula for this one is (Glyoxal, 40% in water)
> C2H2O2 there are also these in my catalog:
> Glyoxal, Dihydrate (trimer) C6H606*2H2O CAS 4405-13-4
> Glyoxal bis (sodium hydrogen sulfite) Adduct, Hydrate C2H4Na2O8S2*xH2O
> CAS
> 517-21-5
> Glyoxal-bis (2-hydroxyanil) C14H12N2O2 CAS 1149-16-2
>
> I've mistaken 2 Glyoxylic acid for Glyoxal when I said 5 or 6, I hope you
> wont hold this against me... I was looking at the formula (Glyoxylic acid
> ,
> monohydrate) C2H2O3*H2O and it seem so close to the first version
> (Glyoxal,
> 40%) that I thought it could be also Glyoxal but it's probably not the
> case.
>
> While I'm at it, I read it's yellow in color, does this color stays in
> the
> gelatine when sizing?
>
> Thanks
> Yves
>
>
>
> ----- Original Message -----
> From: "Katharine Thayer" <kthayer@pacifier.com>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Wednesday, January 11, 2006 9:06 PM
> Subject: Re: Glyoxal?
>
>
> > Hi Yves,
> > Mine from Photographers' Formulary says simply "Glyoxal" and there
> > is a CAS Mixture Number 107-22-2, if that's any help. I am pretty
> > sure this is the standard 40% concentration that most people use for
> > our purposes but suddenly I'm not sure I know how I know that, since
> > there's nothing on the bottle that gives the percent solution. At
> > any rate it works well for me at 3 mls of the solution per 200 ml
> > gelatin solution, which is kind of a standard recommendation, usually
> > expressed as 15 ml per liter of gelatin solution. Or expressing it as
> > grams to grams, hardener to gelatin, as I think Ryuji was
> > recommending, I guess I use 1.2 (g?) of glyoxal (3 ml * .40) per 7
> > grams of gelatin.
> > Katharine
> >
> >
> > On Jan 11, 2006, at 4:43 AM, Yves Gauvreau wrote:
> >
> > > Hi everyone,
> > >
> > > I know some of you use glyoxal when sizing their paper and my
> > > question is
> > > what is the full name of this product or better the chemical
> > > formula???. I
> > > ask because in my catalog I have about 5 or 6 chemicals that could
> > > qualify
> > > as glyoxal.
> > >
> > > Thanks
> > > Yves
> > >
> > >
>
Received on Thu Jan 12 01:39:14 2006