Re: Glutaraldehyde: a different kind of cautionary tale

From: MARTINM ^lt;[email protected]>
Date: 05/06/04-06:24:29 AM Z
Message-id: <000f01c43365$1a417f30$fe0fdb50@MUMBOSATO>

"Do you think ..." hardening "means such different things?"

To me "hardening" relates to a large variety of things:
introducing particular chemical agents by means of a solvent (usually water)
into gelatin. Dozens of such components exist - the patent literature is
full of them. In addition
hardening may also involve subjecting a dry gelatin layer to particular
gases. Moreover there is heat treatment (which may not simply cover baking
but also micro-wave exposure) to provoke strong crosslinking. Heated gelatin
is said to form in situ aldehydes.
Though producing similar effects as more conventional hardeners, I am not
sure whether introducing monomers into a gelatin layer that are subsequently
polymerized, may be regarded as hardening.

It seems to me hardening involves the melting point of gelatin to be risen.
However, this appears to be somewhat ambivalent since gelatin concentration
is likely to have a large impact on gel strength.

"... if it's not impervious to boiling water, then by what criterion is it
considered to be hardened?"

One criterion might be to what degree/at which temperature gelatin is
swelling - that's to say, the quantity of water bound within the layer.


> Katharine Thayer wrote:
> >
> > MARTINM wrote:
> > > " The more I hear about colloid hardening, the less I seem to know
about it.
> > > This might have to do with the vagueness of the term "hardening".
> >
> > Do you think it means such different things? In the leather industry,
> > the test for knowing leather is "tanned" is whether it shrinks in
> > boiling water. I *believe* that properly-hardened gelatin doesn't
> > dissolve in boiling water (am I wrong about that?), and I know for a
> > fact that properly-hardened gum doesn't dissolve in boiling water. So
> > wouldn't being impervious to boiling water be a reasonable criterion for
> > hardening?
> >
> By my criterion above, I suppose glyoxal-hardened gelatin wouldn't
> qualify, as it is said that it can be dissolved in boiling water. But
> if it's not impervious to boiling water, then by what criterion is it
> considered to be hardened? In which case you're right, the term is too
> vague.
> kt
Received on Thu May 6 07:28:55 2004

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