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A Practical Guide to Libun

by Rabbi Dovid Bendory, Av 5767 (July 2007)

Libun is the process of making something kosher by heating it to a high temperature. "Libun" means whitening and refers to heating metal until it glows white, that being a sign that it has reached a high enough temperature. Libun kashers by burning out any tastes that have been absorbed into the utensil undergoing libun.

Libun can be accomplished in several ways. One possibility is to heat the object directly with a flame such as a blowtorch. Given a large blow torch and an object that will withstand such heat, this is typically the fastest way to kasher anything. If the object will not sustain such high temperatures, libun can be accomplished at a lower temperature per the chart below. The item in question should be heated to the given temperature and then maintained at that temperature for the given time frame. Note that thermastat settings on an oven are not exact, so the oven should be set to a temperature higher than the indicated temperature. (I highly recommend reading through the referenced source document from the OU.)

Finally, there are two types of libun: libun kal and libun gamur. Libun gamur is "complete libun" and can be used to kasher any material from any condition, whether from treif to kosher, chometz to Pesach, etc. One need not wait 24 hours before performing libun gamur.

Libun kal ("light libun") is essentially an alternative way of doing hagala. It is useful for situations when hagala is impractical or impossible — such as for kashering an oven from dairy use to meat use or vice versa.

Libun Temperatures
Source: OU
Temperature Time Libun Type
900 F A Few Seconds Libun Gamur
550 F 1 Hour Libun Kal
450 F 1.5 Hours Libun Kal
375 F 2 Hours Libun Kal

Questions to ponder:

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