A discussion of Halachic topics.
For final rulings, consult your Rav
As the Biblical verse above states, not all utensils which become non- kosherby absorbing the taste of non-kosher food can be purged, or koshered. Forinstance, it is impossible to purge "taste" from earthenware. Once anearthenware utensil is rendered non-kosher, it must be shattered and thrown away. On the other hand, metal vessels can be purged of their absorbed tastethrough a procedure called hagalah, purging. The halachos of hagalah are complicated, and what follows is merely an outline of its basic principles.[Unless otherwise noted, the following halachos apply to the Pesach koshering process as well.] Our discussion here refers only to the process of hagalah, not to be confused with other types of koshering such as libun kal and libun chamur, which have different rules altogether.
Utensils made from any type of metal1, stone2, wood3, bone4, leather5, or natural rubber6 may be koshered by hagalah. Earthenware7, china, porcelain8, glassware9 and paper10 utensils cannot be koshered by hagalah11.
The poskim12 differ as to whether hagalah applies to utensils made out of the following materials: Plastic, melmac, nylon, corningware, corelle, pyrex, duralex, enamel, formica, teflon and silverstone. When possible, these utensils should not be koshered by hagalah. In cases of absolute necessity or great financial loss, there are poskim who permit these items to be koshered. A rav must be consulted.
Any utensil which may get ruined during the hagalah process may not be koshered, since we are concerned that its owner will not kosher the utensil properly for fear of damaging it13. If one koshered such a utensil anyway, it should not be used14. However, if it was used, the food that was placed or cooked in it does not become forbidden to eat15.
A utensil becomes non-kosher (or meat or dairy) if it comes into contact with a non-kosher food item in one of the following ways16:
Direct fire: A utensil which is placed directly on the fire with no liquid or minimal oil, butter or shortening added (such as baking pans or parts of a barbecue grill), cannot be koshered by hagalah17. A frying pan18, too, should preferably not be koshered by hagalah.
Indirect fire: A utensil which contains liquid and is placed directly on the fire (such as a pot used for cooking on a range or a spoon used for stirring food in a pot on a burner) can be koshered by hagalah.
Heat contact: Utensils which come into direct contact with hot, non-kosher food, such as a plate onto which hot non-kosher food is placed, a fork with which it is eaten, or a cup into which it is poured, etc. These utensils may be koshered by hagalah. Included in this category are dairy dishes which were inadvertently washed together with meat dishes or vice versa.
Cold Contact: Utensils which come in direct contact with cold non-kosher food must be thoroughly washed with cold water19. Hagalah is not required. If the non-kosher food was a liquid and it remained in the utensil for a period of 24 hours or more, however, hagalah is required20.
Cold "Sharp" Contact: In the case of a cold but "sharp" non-kosher solid food that was cut with a knife21, the knife requires hagalah22. Whenever a utensil needs to be koshered, its cover23 and handles24 need to be koshered as well.
Hagalah purges the "taste" of non-kosher food which is absorbed into the walls of the utensil, but has no effect on actual food, residue or dirt which may be on the surface of the utensil. Accordingly, it is imperative that before the hagalah process begins, the utensil be scrubbed clean of any actual residue or dirt. Rust spots25, too, must be removed, since it is possible that particles of food are trapped between the rust and the utensil. One need not be concerned with rust stains, however, since no food particles can be trapped there26.
Because of this prerequisite, there are several utensils which should not be koshered by hagalah since they cannot be cleaned properly and thoroughly27: Utensils which have crevices or cracks where food may be trapped, a pot that has a cover which is attached by hinges28, a mixer, food processor, blender29, thermos bottle30, sieve, strainer31, grater, grinder, rolling pin, kneading boards32, and anything else which cannot be scrubbed thoroughly and cleaned in every spot where food may possibly be trapped. If hagalah is performed on a utensil which was not completely cleaned, it is not valid even b'dieved and the hagalah process must be repeated.
Handles and covers must be cleaned as well as the utensils themselves. Any handle which is attached with screws should be removed and the area cleaned from food that may possibly be trapped before hagalah takes place. If the space between the handles and the utensil cannot be cleaned, the vessel may not undergo hagalah33.
Our custom (based on several halachic factors) does not allow a utensil to be koshered by hagalah if it was used for non-kosher food within the previous 24 hours34. B'dieved, or in a situation where it is difficult to wait 24 hours, a rav may permit hagalah even within 24 hours under certain specific conditions35.
When koshering for Pesach, it is preferable that the vessel used for the koshering process be either brand new or kosher for Pesach. It is also permitted to use a vessel which was previously used for chametz, provided that 24 hours have passed since it was last used36. The custom is to kosher the vessel itself by hagalah before using it as a receptacle for koshering the other utensils37. After the hagalah, the koshering pot should be put away. If it is needed for Pesach, it should be koshered again38.
When koshering from non-kosher to kosher, the non-kosher utensil should be koshered in a kosher pot39. When koshering a meat utensil which became non-kosher through contact with dairy or vice versa, the koshering pot may be either meat or dairy. Neither the utensils being koshered nor the vessel in which the koshering is being done should be used for the previous 24 hours.
The following is the correct, l'chatchilah procedure for koshering utensils by hagalah40:
Although halachically anyone is permitted to kosher utensils, nevertheless, since the halachos are numerous and complex, hagalah should not be performed without the supervision of a talmid chacham who is knowledgeable in this area. No blessing is recited over the koshering process48.
1 Gold, silver, copper, steel, aluminum, etc.
2 O.C. 451:8. However, what is known today as "stoneware" is not made from stone. It cannot be koshered; ha-Mesivta, 1998, pg. 424.
3 O.C. 451:8.
4 Rama, ibid. See Mishnah Berurah 57 who rules that utensils fashioned out of a horn may not be koshered, since they may get ruined during the hagalah process.
5 Pri Megadim M.Z., end of 451.
6 Igros Moshe O.C. 2:92.
7 O.C. 451:1.
8 Mishnah Berurah 451:163.
9 Rama O.C. 451:26, regarding Pesach. Year-round, some poskim hold that glass never becomes non-kosher; see Igros Moshe O.C. 5:32.
10 Pri Megadim O.C. 451 quoted in Kaf ha-Chayim 126.
11 In certain cases some of these types of utensils may be koshered if 12 months have elapsed since they were last used. This can be done only under the supervision of a rav, since there are several factors involved.
12 There are basically 3 groups of opinions in the poskim regarding koshering these materials: Some allow them to be koshered from non-kosher to kosher but not for Pesach; others allow them to be koshered for Pesach as well, while others do not allow koshering them at all. If at all possible,therefore, koshering these items by hagalah is not recommended. In extenuating circumstances, however, a rav has leeway to permit koshering these materials. It is important to mention to the rav the manner in which these utensils were rendered non-kosher, since many poskim allow these materials to be koshered if they were not in direct contact with fire.
13 Mishnah Berurah 451:23 and 57.
14 See Aruch ha-Shulchan 451:20 who maintains that once done it may be used, but other poskim imply that even b'dieved the hagalah should not be relied upon.
15 Pri Megadim 451:19.
16 There are also other issues which need to be explored before declaring a utensil non-kosher, such as the type of food, the amount of food, the degree of heat, etc. All the facts must be presented to a rav for a decision.
17 Mishnah Berurah 451:27.
18 Rama O.C. 451:11 and Mishnah Berurah 67 and Beiur Halachah.
19 Y.D. 121:1.
20 O.C. 451:21.
21 Mishnah Berurah 447:86.
22 There are conflicting opinions concerning vinegar, etc., that was in a utensil longer than 18 minutes; see Tiferes Yisrael, Pesachim 2:4 and Mishnah Berurah 447:42 and 71; 451:124. A rav should be consulted.
23 O.C. 451:14, since the cover is rendered non-kosher through steam, etc.
24 O.C. 451:12. Even the poskim who object to koshering plastic by hagalah will agree that plastic handles may be koshered; see Shearim Metzuyanim b'Halachah 116:10.
25 We are primarily concerned with rust spots inside the utensil. Rust spots on the outside of the utensil which rarely come into contact with food need not be removed; see Mishnah Berurah 451:43.
26 Mishnah Berurah 451:22.
27 See O.C. 451:3 and Mishnah Berurah 22.
28 Mishnah Berurah 451:44.
29 Rama O.C. 451:18. Se Mishnah Berurah 102 that these utensils pose other problems as well.
30 Mishnah Berurah 451:120 and 156.
31 Rama O.C. 451:18.
32 Rama 451:16 and Mishnah Berurah 94. See also Beiur Halachah.
33 O.C. 451:3 and Mishnah Berurah 23.
34 Rama O.C. 452:2; Y.D. 121:2. Some poskim require that the utensil not be used at all in the previous 24 hours, even for kosher items. Accordingly, the utensil should be scrubbed clean before the 24 hours begin; see Mishnah Berurah 452:20 and Sha'ar ha-Tziyun 25.
35 See Igros Moshe Y.D. 2:31. See also Chazon Ish O.C. 122:6 and Y.D. 23:1.
36 Mishnah Berurah 452:13. See Hagalas Keilim, pg. 221.
37 Sha'ar ha-Tziyun 452:15.
38 Mishnah Berurah 452:10. If the volume of the water in the koshering pot was sixty times greater than the volume of the non-kosher utensil, then the koshering pot need not undergo hagalah, but this is difficult to calculate.
39 Mishnah Berurah 452:13 and Sha'ar ha-Tziyun 16-17.
40 Unless otherwise noted, all the halachos are based on O.C. 452 and Mishnah Berurah.
41 The water should not be dirty or filled with detergents and cleaners. Even if, during the koshering process, the water becomes dirty or tainted, it should be changed before continuing with the hagalah.
42 It depends whether the utensils became non-kosher by being placed directly on the fire or by coming into contact with heat. A rav must be consulted.
43 Sha'ar ha-Tziyun 452:28.
44 Sha'ar ha-Tziyun 452:3.
45 O.C. 451:11. See Hagalas Keilim, pg. 460.
46 Sha'ar ha-Tziyun 452:28.
47 Mishnah Berurah 452:34.
48 See Darkei Teshuvah Y.D. 121:2; Kaf ha-Chayim O.C. 451:200.