A PVA for printing "gum" from Mike Ware

On Mar 29, 2006, at 12:08 AM, TERRYAKING@aol.com wrote:

>
>
> 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.

I don't usually see Terry's posts, but I was looking for something
from Netflix and wondered if it had got into the junk folder, as
things from Netflix sometimes do. (Terry's posts go to the junk
folder, as I've explained before, because my mail program
automatically puts anything that comes from aol into the junk
folder, unless I tell it differently, it came that way, and in this
case for reasons of my own I haven't chosen to override the logic of
the software).

Having seen this one, I'll say this: You can do "simple tests with
commonly available PVAs" if you like, but if you don't know where
the particular PVA you're testing falls on the various parameters
Ryuji listed, you won't know why that particular PVA works, and why
someone using a different PVA may get an entirely different result.
I'm not sure you've grasped that the different PVAs vary not only on
viscosity but on a number of other variables, as Ryuji spelled out.

Then I remembered that in my correspondence with Mike Ware, I told
him that I needed to know a good PVA to use for some work a chemist
was undertaking for me (he got started with that and then got
diverted to his real work and I haven't heard from him for more than
a year) Mike told me that a graduate student of his had worked out a
good PVA for printing. I pulled out the folder and found the
information, and also found that not only had Dr. Ware given me
specific permission to share this information, but had specified
exactly how he wanted it cited. So here it is:

He said that they settled on was a "polyvinyl alcohol-acetate; i.e.
only partially hydrolysed co-polymer, which is much more easily
dissolved in water than the pure alcohol. We found an 88% hydrolysed
PVA, with an RMM around 25 kD in 20% w/v solution, to offer the best
all-around results-- comparable to a 14 Baume Gum."

"If you make any public use of this information in the future, please
acknowledge the original experimenter, by citing:

Stephen Beckett, M. Phil. Thesis, University of Derby (UK), November
1993. (A private communication from Mike Ware)."

So there it is.
Katharine
Received on Wed Mar 29 10:53:28 2006