116:4 Utensils that are used on a fire without water are kashered by purging them with fire (libun). Also, the pots and pans in which chometz had been cooked must be heated until they glow. The libun should optimally be very strong so that sparks fly from the utensil. A baker’s wooden paddle cannot be kashered. 116:5 If a utensil has been patched (in the interior – Mishnah Brurah 451:72) in such a way that the possibility exists that there may be some tangible chometz under the patch, then he must first heat that part until it glows so that he can be sure that if there was some chometz there, then it has been burned up. After this, he immerses the utensil in boiling water. If there is no concern that there may be chometz there, then if the patch was made before the utensil was used for chometz, it can be immersed “as is.” This is because the boiling will draw out the chometz the same way it was absorbed. But if the utensil was first used for chometz and patched later, then the immersion is ineffective for the spot under the patch. Before boiling the utensil in such a case, one must first put hot coals on the patch to make that area glow. If the patch is attached with solder, it can be immersed in the boiling water “as is” because any chometz that may have been absorbed was burned up during the soldering.