Re: archivalness of gum
yes, I was thinking of gum, gelatin or any other materials that can be used
as binder in alt-process printing. I also thought that these binders where
----- Original Message -----
From: "Dave S" <email@example.com>
Sent: Friday, December 21, 2007 2:36 PM
Subject: RE: archivalness of gum
> Yes, but here you are talking about the physical bonding. I think Yves
> question was not about that. We all knew/knew in gum or gelatin bichromate
> printing, the colloid was hardened, so the washing off of the layer was
> a question. I think Yves was asking or suggesting the consideration/study
> whether the colloid would deteriorate in the long run and so I suggested
> comparison with paintings.
> And I didn't say the gum makes the watercolor permanent either. I was
> that the gum itself holds up after hundreds or thousands of years. In
> traditional brush paintings, there is a method where the gummed pigment is
> applied to unsized paper (where the pigment would heavily permeate the
> paper), but there is also another method of sizing the paper first and
> carefully paint on the sized paper. The size used is typically gum or
> glue + alum, so it is very similar to what we use in gum bichromate
> painting. And the painting would stay on top of the sized layer.
> And both type of paintings survive hundreds if not thousands of years.
> If we are considering physical properties, then I think our concern is
> whether the hardening process would harden the colloid in such a way that
> becomes brittle in the long run and so while the pigment and the colloid
> archival in themselves, the picture would "fall out."
> And yes, we are getting into different aspects of archival. Lightfastness,
> chemical reaction to surrounding environment, physical attachment, are
> of those aspects; and we have talked about all these at different times.
> > -----Original Message-----
> > From: Katharine Thayer [mailto:firstname.lastname@example.org]
> > Sent: Friday, December 21, 2007 2:01 PM
> > To: email@example.com
> > Subject: Re: archivalness of gum
> > On Dec 21, 2007, at 9:47 AM, Dave S wrote:
> > > Yes, but since gum arabic has been used in painting, the
> > archivalness
> > > of it has gone through time test for a long time, from hundreds to
> > > thousands of years.
> > Well, yes and no.
> > The gum arabic in watercolor paint is highly water soluble
> > and remains so; the permanence of the image has less to do
> > with gum arabic than with the fact that pigment stain, as
> > most gum printers have observed, is completely
> > indestructible. Watercolor paintings are essentially made of
> > pigment stain, and owe their permanence to
> > it. Try adding more gum to watercolor paint and painting with
> > that, and see how permanent that painting is. Even after
> > drying the painting for months, all you have to do is run a
> > wet brush across the paint, and it's gone. You could keep
> > the painting intact by making sure water never got near it,
> > but I don't know... as Ryuji and Gawain said, there are
> > different definitions of what makes something archival, but
> > to me an image that's highly water-soluble doesn't fit the
> > bill. So it's not the gum that makes a watercolor painting
> > permanent, but the fact that the pigment has permeated the
> > paper and stained it permanently.
> > On the other hand, properly crosslinked gum, as in a finished gum
> > print, is insoluble in water, so it's a different animal
> > altogether.
> > I've tried pouring boiling water on it from a height even,
> > with no effect on the hardened gum.
> > Myself, I consider gum quite archival; the only thing I'm
> > objecting to here is categorical pronouncements based purely
> > on speculation.
> > Katharine