As It Absorbs, So It Expels
כבולעו כך פולטו
As we have learned (above 32:1), the fundamental rule in the laws of kashering utensils is ke-bol’o kakh polto (“as it absorbs, so it expels”) – the manner in which the utensil was used with a prohibited substance determines the manner in which it is kashered. There are three types of kashering: 1) hadaḥa (rinsing); 2) hag’ala (purging); 3) libun (heating to incandescence). Let us explain further: the first type is hadaḥa with water, which is the lightest form of kashering, intended for utensils that were used with cold forbidden foods; to kasher them, one must rinse them with water and clean them of the remnants of forbidden food that remained stuck to their walls. The second type is hag’ala in boiling water, intended for utensils in which forbidden foods were cooked. Hag’ala connotes expulsion, for placing the utensil in boiling water causes it to expel the flavors that were absorbed in and stuck to it through cooking. The third type is libun with ur (fire), intended for utensils that were used on fire, such as skewers and grilling racks.¹
The difference between the three types of kashering is as follows. When utensils were used with cold food, the food remnants stick to the utensils externally, and hadaḥa washes them off and kashers them. When utensils were used for cooking, the cooking causes the flavors of the foods to stick to and be absorbed in the utensils more strongly; therefore hadaḥa will not help them, and they can be kashered only through hag’ala in boiling water, which dissolves the fats and expels the flavors that stuck to and were absorbed in the utensil. And when utensils were used on fire (ur), for roasting or baking, the flavors stick to and are absorbed in the utensils with great force, and more tenaciously than in cooking, because cooking is done with liquids that soften the absorption and adhesion of flavors. In addition, cooking is generally done at a temperature not exceeding one hundred degrees, because the liquids in the cooking moderate the rise in temperature, whereas baking and roasting, which are done without liquids, are done at a higher temperature. Therefore hag’ala in boiling water can expel only some of the flavors that stuck to and were absorbed in the utensil through fire, and in order to eliminate them one must heat the utensil in fire to incandescence, which will burn and consume the flavors absorbed in the baking pan or skewer. It emerges that as a rule hag’ala expels and extracts the flavor stuck to and absorbed in the utensil, whereas libun burns the flavor while it is still inside it.
Notes (1)
- Mishna (Avoda Zara 75b): “One who purchases utensils from a gentile: that which is normally… purged – he must purge it; heated to incandescence in fire – he must heat it to incandescence in fire. A skewer and a grill (grilling rack) – he heats them to incandescence in fire. A knife – he polishes it (scours it), and it is pure.” An elaboration in the baraita there: “The Sages taught: One who purchases utensils from a gentile – things that have not been used, he immerses them and they are pure (in accordance with the law of immersion of utensils explained above in chapter 31). Things that were used with cold food, such as cups, pitchers, and flasks – he rinses them and immerses them and they are pure. Things that were used with hot food, such as kettles (large pots), kumkumusin, and water heaters – he purges them and immerses them and they are pure. Things that were used on fire, such as skewers and grills – he heats them to incandescence and immerses them and they are pure….”