Re: archivalness of gum
Dave, 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 hardened. Yves ----- Original Message ----- From: "Dave S" <fotodave@dsoemarko.us> To: <alt-photo-process-l@usask.ca> 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 not > a question. I think Yves was asking or suggesting the consideration/study of > whether the colloid would deteriorate in the long run and so I suggested the > comparison with paintings. > > And I didn't say the gum makes the watercolor permanent either. I was saying > 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 then > carefully paint on the sized paper. The size used is typically gum or animal > 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 it > becomes brittle in the long run and so while the pigment and the colloid are > 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 some > of those aspects; and we have talked about all these at different times. > > > Dave > > > -----Original Message----- > > From: Katharine Thayer [mailto:kthayer@pacifier.com] > > Sent: Friday, December 21, 2007 2:01 PM > > To: alt-photo-process-l@usask.ca > > 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 > > > > > >
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