Clean the kettle, inside and out to make sure you remove any loose debris. Scrub it with a coarse steel wool pad and dish soap. Rinse the kettle with warm water.
Wipe the interior and exterior of the kettle with a paper towel to remove the excess moisture.
Smear a generous amount of lard over the interior and exterior surface of the kettle, wiping it in circles with a cotton rag until you have greased the entire pan. Use another paper towel to remove the excess.
Bake the kettle for an hour at 300 F to cook the surface back on the pan. Check to see if the fat has changed to a smooth, shiny surface. Repeat the process two or three times if your kettle is especially pitted.
Remove the pan from the heat and allow it to cool. Your cast iron kettle is ready for use.