I washed the print between sheets of reemay in a filtered* water bath (Top). This removed most of the staining. Some areas were worse than others, so I removed them using filtered water on a vacuum suction table. I dried the print in the drying rack, and then reintroduced moisture using Gortex and pressed the print under weight to flatten it again. The picture on the bottom shows the corner after washing.
A friend of mine was dog sitting, and the puppy urinated on a print she had leaned against the wall. The original matte and foam core were badly stained. Luckily only the lower right-hand corner of the print was affected. In order to remove the urine, the print needed to be washed. I first tested the inks by wiping small areas of each color with damp q-tips. This is a before picture of the corner.
The foam core was completely ruined. The artist statement was attached to the back of the foam core, but was not affected by the urine stain. However, twenty years had made it highly acidic. After removing it from the foam core, I washed it between reemay in filtered water, then deacidified it with a magnesium bicarbonate solution (Mg(HCO3)2). These images show the before (Top) and after (Bottom).
*The Syracuse University lab does not have de-ionized water. Instead, the water is run through a particle and charcoal filter.