This means: light libbun, and it is used to kosher cooking utensils for Passover. It is not a replacement for libbun gamur, since it is less effective. It is, however, a replacement for hagalah.
It should be noted, that, in special cases, libbun kal may be a replacement for libbun gamur. This applies, only prior to Passover, and only if there are other reasons to be lenient.
Points to Keep in Mind about Libbun Kal
The utensil may be koshered by libbun kal, even if it was used within 24 hours.
Once a utensil is koshered for Passover use, it emits everything which is absorbed in it. Therefore, one may use a utensil which was previously “meat” for “dairy” and vice-versa, after koshering the utensil for Passover use.
On Passover itself (during Hol Hamoed, the intermediate days), libbun gamur or libbun kal—may be performed, while hagalah may not be performed. Therefore, if one has a utensil that is normally koshered by hagalah, and the individual wishes to kosher that utensil on Passover from hammets to Passover use, it should be koshered by libbun gamur or libbun kal.
When a large utensil cannot be placed in the fire completely, it may be partly placed in once, then partly placed in again, until all of it is placed in.
Following libbun kal, it is not necessary to place the utensil which was koshered into cold water.
There is no berachah upon libbun kal.
How to Do Libbun Kal : A Step-by-Step Guide
The procedure to be followed should be:
1. Clean the item thoroughly.
2. Sufficient heat must be brought to the item that is being koshered, so that, if a piece of straw were put, not on the side of the item that is receiving the direct heat, but, on the other side of the item—that straw would burn.
If this is done with direct heat (such as a blowtorch), the other side of the item must reach a temperature of 160 degrees, Fahrenheit.
If this is done with indirect heat, such as, by placing the item in an oven, the heat level and duration of time to accomplish this—have been determined to be:
➢ 550 degrees for an hour.
➢ 450 degrees for an hour and a half.
➢ 375 degrees for two hours.
(This can also be accomplished with a blowtorch.)
3. Remove the item from the heat.
To see a comprehensive list of various utensils and the methods of koshering them, click here