Urine and Uric Acid on Ivory Object

Hello again! We’ve been busy with historic preservation tasks, so I’ve been remiss in blogging about our adventures. We recently were hired by a private collector to restore her carved, Japanese Ivory sculpture from the mid 1850s. It had been involved in a crime scene in nearby Mississippi where it was urinated on, and then had a polymer-based floor sealer splashed on it. Straight out of a John Grisham novel! A few pieces of the beautiful carving had also broken off when the sculpture was knocked off its pedestal.

We looked into several trusted resources, and…surprise, surprise…there’s not much information out there on how to remove floor sealer and urine from antique ivory. The MSDS sheet for the floor sealer confirmed our worst expectations that it was essentially non-removable without sanding or scraping. None of the regular, trusted solvents would work.

The urine was another issue. Apparently, urine can have very different properties depending on the producer’s diet and medications. Since our producer was in jail, we didn’t have that information available. We gently but thoroughly cleaned the entire object, and then settled in for the biggest challenge. Where the urine and floor sealer had originally contacted each other (both wet), they formed weird yellow crystals on the surface. These crystals were extremely brittle. It turns out that when uric acid comes into contact with the right types of simple polymers (like those in our floor sealer), that a reaction can occur and a crystalline structure gets created. We found that the best method of removal was to use rubbing alcohol to significantly soften the crystals, and then gently use a very sharp blade to scrape them off the surface. These crystals turned out to be much easier to remove than the floor sealer alone.

Always glamorous happenings in the world of materials conservation!