Can I use Wood Preservatives on wood that has already been treated with a varnish, clear coat sealer, or any other type of coating system?
Wood Preservatives should be applied before treating with stains and water sealers and cannot be applied over new varnish or paint. The preservatives would not penetrate into the wood enough to be beneficial. The only exception is if the stain or water sealer is very old (more than 5 years), then Wood Preservatives can be applied without risk of damaging the old finish.
