Re: New Gloy = Bakerex & PVA Criteria for making gum prints.

Katherine and Ryuji are off on a side track.

.Specific gravity is a guide to whether the material will help us to make
gum prints. If it is too light , or thin, highlights are likely to be
contaminated. If it is heavy, the mixture will not, among other things, coat properly.

The criterion here is whether the material will do the job we demand of
it.

Simple tests with commonly available PVAs will show us.

Terry

In a message dated 29/3/06 2:12:51 am, kthayer@pacifier.com writes:

> Thanks, this is what I was trying to say,  but Ryuji said it with 
> more precision and specificity.
> Katharine
>
>
> On Mar 28, 2006, at 4:43 PM, Ryuji Suzuki wrote:
>
> >> In a message dated 28/3/06 4:45:46 pm, kthayer@pacifier.com writes:
> >>
> >
> >
> >>> (get some PVA of whatever kind (although the
> >>> degree of hydrolysis should be high regardless)  some glycerine, 
> >>> some
> >>> water; mix them together in proportions of your choosing until it
> >>> seems about right)-
>
>
> >
> > Degree of hydrolysis varies a lot. Higher degree of hydrolysis would
> > increase adhesion to hydrophilic surfaces, but not hydrophobic; the
> > reverse for low hydrolysis PVA. Higer hydrolysis would result in
> > increased tensile strength, and lower, increased flexibility. It is
> > probably easiest to test the degree of hydrolysis by testing for water
> > sensitivity or emulsifying power.
> >
> > Incidentally, the different degree of polymerization would result in
> > different viscosity, as well as water sensitivity, adhesion,
> > emulsifying power, etc. It's best to determine viscosity first.
> >
> > From: TERRYAKING@aol.com
> > Subject: Re: New Gloy = Bakerex
> > Date: Tue, 28 Mar 2006 10:52:01 -0500 (EST)
> >
> >
> >> Viscocity is sufficiently related to specific gravity for our 
> >> purposes.
> >>
> >
> > This is not true. SG of pure PVA is about 1.27 to 1.31 and is related
> > to degree of crystallinity.
> >
> > Like I said in earlier posts, there are several important variables in
> > variations of PVA and water content is not the only difference in
> > proprietary products. If any of these is important to your
> > application, trying to figure out proprietary products is waste of
> > time. Just buy one that comes with information on the exact
> > composition from the original chemical manufacturer.
> >
>
>
Received on Wed Mar 29 02:08:48 2006