Re: GUM-PVA-COLD preshrink

What exactly is the purpose of preshrinking in hot water? I do it because
the book told me to. I rarely develop a print in anything above say, 80
degrees.

Candace Spearman

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, May 24, 2005 4:19 AM
Subject: Re: GUM-PVA-COLD preshrink

> Hi Henk,
>
> henk thijs wrote:
> >
> > Dear List,
> > Last month I saw a demo by a belgian gummist -Jean Janssis- who seems
> > to be a professional in that sense that he makes a living of it and he
> > had exhibitions even in New York.
> > The good thing is he had some astonishing gumprints of nearly 70 to 90
> > cm (circa 28 by 36 inches).
> > So I tried to ask him some questions; the only english -or german, or
> > dutch - word he coiuld reply was 'help', and my french is really not
> > good enough to discuss things.
> > What I understood is:
> > he uses Hahnemuehle 350 grs aquarelles paper (or Arches) and wenn I
> > explained that I want to know things like: preshrink, gelatine,
> > glyoxal, he made clear that he made the preshrink in cold water, half
> > an hour, several times, and there was NO need for gelatine-glyoxal. He
> > made clear to me that due to the cold water, the paper contains still
> > the original sizing, it's what he said , and he sells.....even in the
> > states.
>
> This makes sense, actually. I think it's been fairly well established by
> now that hot water can disrupt the factory sizing in some papers in a
> way that affects the print negatively. I can't speak to the issue of
> cold shrinking from my own experience, because for most of my gum
> printing experience I've printed everything including tricolor gums on
> paper that's neither preshrunk nor sized, and for the rest of it I've
> printed on paper that's brush-sized but not shrunk. So as I say, I can't
> say from my own experience that preshrinking in cold water obviates the
> need for sizing, but it makes sense to me, although it probably wouldn't
> work the same for all papers.
>
>
> > He did not use gum-arabic , but some stuff called 'MOWIOL 8-88', it is
> > an PVA.
>
>
> > He also uses only vanDijckbrown
>
> I hope he knows, and doesn't care, that VanDyke brown (NBr8) is a
> fugitive pigment.
>
> as a pigment ( a kg at a time ) , this
> > due to the big amounts necessary for the large prints.
> > So, I really was impressed by the quality of the prints and I looked
> > for MOWIOL and bought some.
> > But I have no clou how to handle the stuff.
> > I looked in the archive and found some stuff about PVA, but I have not
> > enough chem. background to go with it. Any comment is welcome :-)
>
> I haven't printed with PVA by itself, but I've printed with gloy, which
> is probably mostly PVA, and found, with a small sample of two or three
> prints, that it printed pretty much like my usual gums: same mixture,
> same exposure, same development, and that it gave the same number of
> steps (8) as the Daniel Smith premium gum I compared it with. So I'd
> recommend starting with your usual procedure, and adjusting if
> necessary. The chemist I'm working with says he believes that the
> chemical mechanism (yet to be discovered) for the crosslinking of gum is
> probably the same as the chemical mechanism for the crosslinking of PVA.
> To date all we have in the literature to point us toward the
> crosslinking of gum is research on PVA crosslinking. Good luck,
> Katharine Thayer
>
Received on Thu May 26 06:33:53 2005