Re: gloy for tricolor on yupo? (revision) PVA and Gum

In a message dated 4/4/06 3:29:19 pm, alt_list@albertonovo.it writes:

> TERRYAKING@aol.com wrote:
>
> > specific gravity is a factor in the expression of viscocity even in
> industrial
> > measuring devices
>
> Don't keep things too simple...
> Viscosity is due to the action of internal forces among the molecules, while
> density is simply the ratio weight/volume. For most of the organic
> substances viscosity is related to the molecular weight.
> The empirical relation between density and viscosity is valid for each
> substance, so that in an industrial process where the same substance may be
> more or less diluted, density may be used instead of viscosity.
>
> > We were told that one should choose aq PVA which corrsponds best to 14
> Baume.
> > In fact one can vary the specific gravity ( Baume is a scale of specific
> > gravities of heavy liqids) by varying the amount of water..
>
> In my opinion one should dilute his PVA until it feels like his gum when
> brushing. That is, viscosity (and not density) is more or less the same.
>
> As for PVA and gum arabic print definition, I would suggest to consider in
> this group also caseine and egg (temperaprint) prints. I never tried, but I
> think that also a starch glue should work...
>
> Alberto
>

Alberto

In essence we are agreed on all these points. That is an indication of why it
is so important to keep things simple. By delving too deeply one one can find
nice distinctions which are of no practical significance in making gum
prints. That is what has been happening here.

You are right one can make 'dicromate' prints from all sorts of plant and
animal substances. I had one student whose prints were made from her own milk
while another, whose specialisation at the time was homo erotic photography,
asked her models for bodily fluids which made some interesting prints. The rumour
got round that we were making them in class !

Terry

Terry King FRPS

RPS Historical Group (Chairman)

www.hands-on-pictures.com/

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Received on Tue Apr 4 09:03:33 2006