Hagalah

In Jewish law, Hagalah is a procedure performed in order to make fit for use cookware, bakeware, and utensils that were previously used with non-kosher foods in a way that caused the absorption of non-kosher flavors into the walls of the utensil.

Hagalah is also done in order to use utensils for dairy cooking after meat was cooked in them, and vice versa, or for using utensils during the Passover holiday after they were previously used with chametz (leavened products). Generally, the kashering is done in the same way that the non-kosher substance was absorbed into the walls of the utensil ("just as it absorbed, so it expels").