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
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.