It's not reversible, unfortunately. The polyurethane breaks down through hydrolysis. Keeping it in a dry environment is the best you can do. Apparently you ca

It's not reversible, unfortunately. The polyurethane breaks down through hydrolysis. Keeping it in a dry environment is the best you can do. Apparently you can slow it down by driving the water out with heat, but that won't fix the already broken down PU.