Re: gum arabic
Loris, There are three questions here. Does gum when used as a pigment binder have a long and effective history with little or no record of darkening? I think the answer is yes. Is a thick layer of gum used as a varnish wise? The Williamsburg example says no. Is hardened gum going to darken over time? Beyond the 120 years that it has been know to be used we don't know.
My point was not to assert that hardened gum was not going to discolor. I just feel that the Williamsburg example of gum used as a varnish while interesting it is not proof of anything directly relevant to gum printing. I see your concern for our finite information on hardened gum. It would be nice to have more info on hardened gums durability. My response was to point out my opinion that the example of gum as a pigment binder going back to ancient times is more like our practice of printing than an example of a thick layer of gum used as a varnish.
Sorry if I was not clear,
2009/1/31 Loris Medici <email@example.com>
But in a gum print the gum and the pigment(s) are inseparable. So, to me