Re: was: glyoxal yellowing now: How do you know it's hard?

From: clay <wcharmon@wt.net>
Subject: was: glyoxal yellowing now: How do you know it's hard?
Date: Thu, 03 Feb 2005 11:26:12 -0600

> The whole gelatin hardening debate makes me wonder if there is any real easy
> way to tell if it(the gelatin) is hardened enough. Is it an on/off thing,
> where it is either hardened or not, or are there degrees of hardness? My
> question is asked because the amount of hardening agent should ideally be
> just the minimum needed to cause the gelatin to harden enough to keep
> highlights nice and clean.

Degree of gelatin hardening is usually measured by the thickness of
the dry layer and that of swollen layer of the same coating. It is
also sometimes measured by "melting point" where the gelatin is
immersed in water of various temperatures and see at what temperature
the gelatin becomes sol form.

I am not sure if there is any adverse effect by hardening the sizing
layer to a degree harder than necessary. For the image forming layer
in silver gelatin process, covering power and Dmax suffer when the
gelatin is hardened too much, so generally hardening is adjusted to
give about 300% swelling.

--
Ryuji Suzuki
"People seldom do what they believe in.  They do what is convenient,
then repent." (Bob Dylan, Brownsville Girl, 1986)