Rabbi Moshe Feinstein, in Igrot Moshe, writes that if the crockery has not been used for at least a year it can be used after a proper “koshering” process. One should immerse the crockery in boiling water three times in order to Kosher it. The water must be so hot that when the articles are placed in it the water continues to bubble. After immersion in the boiling water they should be removed (not with your hands!) and then placed in cold water.
