Re: polivinyl alcohol vs. gelatin sizing

Hi Katharine,
Thanks for your reply.
Let's be very clear, which one is Elmer's glue made from?
The acetate or the alcohol?
You said the alcohol version behaves as the gum meaning, once is hardened
does not dissolve in water?
If so why do you bother with the acetate?
When you said PVA is acetate or alcohol?
Yes, there is a confusion between them.
Giovanni

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, July 30, 2005 4:04 AM
Subject: Re: polivinyl alcohol vs. gelatin sizing

> Giovanni Di Mase wrote:
> >
> > Hi list,
> > As anybody worked or tested the polivynil acetate or alcohol (it is
> > found in Elkmer glu) as a substitution to gelatin for sizing paper?
> > Thanks,
> > Giovanni
> Katharine Thayer wrote:
> >
> > Hi All,
> > I don't understand what the advantage would be over simply sizing with
> > acrylic medium, diluted to about the same strength? It seems to me that
> > they are similar enough that the effect should be about the same. Or am
> > I missing something.
>
> Giovanni Di Mase wrote:
> >
> > You don't need hardener with the acrylic.
> > It is more even than a perishable gelatin
> > It is not affected by humidity.
> > Easier coating.
> > Many others but just try it.
> > Giovanni
>
> Giovanni,
> Be careful not to confuse the two PVAs; polyvinyl acetate and polyvinyl
> alcohol are two different animals. Polyvinyl alcohol is soluble in water
> and behaves just like gum: dried unhardened PVA dissolves in water, just
> as gum does. That's why PVA can be used as a substitute for gum in the
> gum process and behaves very similarly to gum in the process.
>
> Polyvinyl acetate is different in that it does not dissolve in water and
> in order to dilute it to spreading consistency you would have to use
> some other solvent.
>
> I don't understand your answer to my question about why one would use
> PVA rather than acrylic medium. It's true that polyvinyl alcohol would
> require a hardener, but that would be a reason to use acrylic, not a
> reason to use PVA. And so on. So maybe my question wasn't clear; I
> still don't understand why PVA rather than acrylic.
> Katharine
>
Received on Sat Jul 30 14:29:37 2005