RE: Questions on hardening gelatin

From: Keith Gerling ^lt;[email protected]>
Date: 10/03/05-03:25:21 PM Z
Message-id: <DIEJIODOMMCOAHNJNAFCGEDNCAAA.Keith@GumPhoto.com>

Interesting. I thought I had read here that chrome alum was very slow -
requiring a week to do it's job.

Thanks

Keith

-----Original Message-----
From: Ryuji Suzuki [mailto:rs@silvergrain.org]
Sent: Monday, October 03, 2005 11:42 AM
To: alt-photo list
Subject: Re: Questions on hardening gelatin

Ian Robinson of du Pont de Nemours did a study on this and published in
J. Appl. Polymer Sci., 8, 1903-18 (1964). At pH of 6, and at 10% gelatin
concentration, crosslinking reacion is in the order of (from fast to
slow): glutaraldehyde, chrome alum, formaldehyde, glyoxal, dimethylol
urea.

Tabor, Owers and Janus of Kodak Harrow did more extensive kinetic study
(J. Photo. Sci., 40, 205-211, 1992).

With aldehyde hardeners like glut, glyoxal and formaldehyde, you can
make them work faster by putting more hardener. However, this way you
will expose yourself to more aldehyde vapor. (Glut is the fastest, so it
is best to use minimum amount of glut. The glut reacts with gelatin
before much of it vaporizes.) Or you can prepare thicker solution of
gelatin, to which the hardener is added at the same proportion(*) and
coated thinly.

* people on this list seem to calculate percent hardener in the total
solution volume, but the hardener-to-gelatin ratio is most directly
relevant.

On Mon, 03 Oct 2005 09:07:50 -0700, "Keith Gerling" <Keith@GumPhoto.com>
said:
> I'm wondering if someone could comment on the length of time it takes for
> the various gelatin hardeners to perform the hardening function. It is
> my
> understanding that gluteraldahyde will harden in an hour or so, and that
> chrome alum takes a week. How does glyoxal and formaldehyde compare?
>
>
>
Received on Mon Oct 3 13:24:30 2005

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