Boiling water--with the occasional submersion in dirt
• If you use a dairy knife to cut cold or slightly warm meat;
• If you want to use a meat knife to cut pareve bread for a dairy meal;
• If you only have an unkosher knife at hand. Use ne'itzah so you can use it temporarily;
• If, when cutting vegetables, you inadvertently cut a worm.
What the preceding circumstances all have in common is that the foods are cold, or at least below yad soledet bo ["when the hand shrinks back from it" because of the heat--the point at which Jewish law considers a liquid hot]. Knives that you use for cutting hot meat, such as those that are part of a set of flatware, still need to be kashered through boiling, hag'alah. A serrated knife, however, because of its nooks and crannies, needs the higher heat of libun for kashering; that is, the knife has to be heated with a blowtorch until it is red hot.
You may need to get a new set of knives. Many great cooking knives have bolted plastic or wooden handles; few are one continuous piece, and there is the real possibility that unkosher food might get caught between the various cracks. Check with your rabbi.
Selections from How to Keep Kosher, by Lise Stern. Copyright (c) 2004 by Lise Stern. Used by permission of HarperCollins Publishers Inc.
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