Re: dichromated colloids

"This is interesting to me in the context of reading a paper today that
claims that some of Eder's results were due to impurities in the gelatin."

Taking into account the complexity of the chemical structures of gelatin and
gum, I wonder if it's not next to impossible to get standardized gum or
gelatin (at least in respect to photographic applications). And maybe the
vagueness, lack of reliability we generally attribute to those past formulas
taken from old photographic books actually relates to that deficit.

Martin

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, May 21, 2004 12:08 AM
Subject: Re: dichromated colloids

> MARTINM wrote:
> >
> > "In short, I think the purity of PVA, especially in terms of per cent
> > -COOH in the long alcohol, kinda like mixed poly(vinyl alcohol/acrylic
> > acid) is the source of disagreeing results. Another possible impurity
> > might be a redox catalyst, like some transition metals. I think
> > Mannivanan, Lafond, and those groups pay some attention to the purity
> > of PVA, and some other studies were done with PVA containing some
> > impurities. One of their study says Cr(V) is stable in PVA. Then, it's
> > natural not to see Cr(III) absorptions right away."
>
> So if I understand you right, you think the reason Mannivannan couldn't
> assess whether the chromium was complexed with the PVA is because of
> impurities in the PVA? Could you expand on the last two sentences?
> Martin may see, but I don't quite.
>
> This is interesting to me in the context of reading a paper today that
> claims that some of Eder's results were due to impurities in the
> gelatin.
>
>
> >
> > I see. I guess purity may always be an issue - even more so where
gelatin
> > and gum are involved...
> >
> > "I'm not attached to gum in any way, but I think this is about time for
> > someone to run a series of analogous experiments with gum. I don't
> > know if holography community studies gum, but if not, I don't think
> > anyone is really interested in doing (or funding) it anyway."
>
> I don't know where the money would come from. All the gum money is in
> food, and all they want to know about is "mouth-feel" and stuff like
> that. They wouldn't be interested in dichromated gum unless you could
> eat it.
>
> >
> > To the best of my knowledge very little attention has been paid to
> > dichromated gum. I am not aware of any papers specifically dealing with
gum.
>
> I sure have scoured the chem abstracts in vain.
> Katharine
Received on Fri May 21 03:34:25 2004