RE: polivinyl alcohol vs. gelatin sizing

From: Schuyler Grace ^lt;[email protected]>
Date: 07/30/05-12:19:07 PM Z
Message-id: <E1DyvvJ-0005J5-00@pop-knobcone.atl.sa.earthlink.net>

KT (or anyone else who might know),

Is there any advantage to using PVA as a gum replacement, or is medium for
gum printing just a choice of what's readily available (or is GA a better
medium, for that matter)?

-Schuyler

-----Original Message-----
From: Katharine Thayer [mailto:kthayer@pacifier.com]
Sent: Saturday, July 30, 2005 1:05 AM
To: alt-photo-process-l@sask.usask.ca
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 12:19:16 2005

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