Re: polivinyl alcohol vs. gelatin sizing

Thanks Katharine.
You just spare me to test that.
What about using PVA alcohol or acetate for sizing?
In my case I was able to have bot chemicals separated and not confused but I
am trying to figure out which one is good for what.
Kevin said to me that the acetate works for sizing and he uses but that was
it, I haven't get any further info.
Giovanni

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, July 31, 2005 4:55 AM
Subject: Re: polivinyl alcohol vs. gelatin sizing

> Ryuji Suzuki wrote:
> >
> > From: Giovanni Di Mase <gdimase@hotmail.com>
> > Subject: Re: polivinyl alcohol vs. gelatin sizing
> > Date: Sat, 30 Jul 2005 16:28:30 -0400
> >
> > > Let's be very clear, which one is Elmer's glue made from?
> >
> > The main ingredient is poly(vinyl acetate) and water.
> >
> > > When you said PVA is acetate or alcohol?
> >
> > PVA is an ambiguous acronym. Some people use PVOH to indicate
> > poly(vinyl alcohol) to avoid confusion.
> >
> > > Yes, there is a confusion between them.
> >
> > There is no confusion in terms of chemistry. The confusion is just in
> > acronyms. It's also that vinyl acetate and vinyl alcohol are often
> > used as copolymers and also as mixtures of multiple copolymers in
> > practice to achieve desired properties. One example I gave was acrylic
> > medium.
>
> Perhaps, but in practice, which is what I think we're talking about
> here, they behave very differently. You can use polyvinyl alcohol as the
> colloid in the gum process. You can't use polyvinyl acetate or acrylic
> to print gum with, as neither of them will dissolve once dry, and the
> polyvinyl acetate won't mix with the dichromate; it just precipitates
> into little clumps of gunk. (I found this out once when I bought
> something called PVA glue, assuming it was polyvinyl alcohol). So it
> doesn't make sense in terms of practice to talk about them as if they
> were interchangeable.
> Katharine Thayer
>
Received on Sun Jul 31 10:11:05 2005