Vintage Planters Vintage McCoy Planters, How To Clean?

Vintage McCoy planters, how to clean? - vintage planters

I've recently bought a very nice vintage McCoy Pottery planters. They are certainly be used for many years. Does anyone know a way to hard water deposits and salty foods, which are attached to the pot you? I tried soaking in vinegar, but it has not even a breakthrough. Any suggestions would be great. I want to return with them, but I make sure that the plants stay healthy.