Acrylic sizes for gum (Re: Gum print formaline

Kate,
I wonder how this Rhoplex is different from the regular acrylic medium.
I tried mixing acrylic medium with gelatin once and found that the
acrylic medium in gelatin produced a sizing that couldn't stand extended
soaking; if it was in water for more than half an hour, the sizing would
break down and the image would break up into a grainy splotchy image.
Unfortunately I didn't note what concentration I used, and I didn't
bother to try different concentrations to see if it would help, I just
ditched the whole idea after this first unfortunate result. So I'll be
interested to hear if this Rhoplex works better for you than the acrylic
medium did for me.
 
As far as that goes, acrylic medium by itself makes a pretty respectable
size, in my experience. The two main things to remember with this are
(1) to dilute it enough. Some of the books say 1/4; this is way too
much, it makes a slick plastic surface that gum just slides right off
of, in my experience. I find that 1:10 works well, see example here

http://www.pacifier.com/~kthayer/html/Whiteblack.html

but of course it depends on your brand of acrylic. I use Daniel Smith.

(2) use gloss medium rather than matte. Gloss is the straight medium;
matte includes additives intended to cut the gloss. I don't know what
the additives are exactly but some sources say that wax or waxy
substances are added; at any rate in my experience matte medium doesn't
work as well as gloss medium for sizing for gum. At the effective
dilution range, there's not actually any shine. I haven't used acrylic
medium extensively, but think it's worth a look for someone who wants
another option.
Katharine

Kate M wrote:
>
> Thanks Ryuji I just happen to have a LARGE botle of this medium for
> painting!
>
> -----Original Message-----
> From: Ryuji Suzuki [mailto:rs@silvergrain.org]
> Sent: Friday, 4 February 2005 9:27 a.m.
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: Gum print formaline
>
> From: Kate M <kateb@paradise.net.nz>
> Subject: RE: Gum print formaline
> Date: Fri, 04 Feb 2005 08:36:26 +1300
>
> > When I find a paper that doesn't allow printing several layers without
>
> > some staining, or for some other reason needs to be sized (such as
> > Fabriano Uno which printed with an attenuated DMax without sizing)
> > then I do size it, but my favorite size is gelatin mixed with gesso,
> > which gives a lovely smooth surface and you can even do it indoors.
>
> When someone brought up gesso last time I tried it, but it was too
> gritty and I didn't like it.
>
> What I use instead is Roam and Haas Rhoplex AC-35 (methacrylate and
> poly(vinyl alcohol-co-vinyl acetate) made as a plain medium for acrylic
> paints). It makes the sizing layer more durable but too much of this in
> relation to gelatin would make even brush coating of the emulsion much
> more difficult. (Coating rods, etc. should be fine.) But when used in a
> small quantity it works very nicely with all methods of coating.
>
> --
> Ryuji Suzuki
> "People seldom do what they believe in. They do what is convenient,
> then repent." (Bob Dylan, Brownsville Girl, 1986)
>
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Received on Thu Feb 3 19:29:05 2005