Kashering

One may not perform hag’alah on equipment made of cheress/ceramic, and a common home example of that is a coffee mug. [Other possible examples such as bricks, cement, concrete, china, glass, granite, porcelain enamel, rubber, stone, and wood will be discussed in chapters 24, 50, 52, and 56].

In a factory setting, there are three places where cheress might be found: homogenizer pistons, packing in a distillation column, and as a filter for a liquid such as juice. If these are present in equipment, that part of the factory would essentially be impossible to kasher.

Contemporary Poskim disagree as to what status to assign to plastic and other synthetic materials, as relates to kashering. One group understand that all materials can be kashered except for those specifically excluded by the Torah. Others take exactly the opposite approach and contend that we may only perform hag’alah on those which the Torah and Gemara specify as qualifying. If so, plastic cannot be kashered.

In practice, most Israeli Poskim and American hashgachos accept the lenient approach, while one major American hashgachah and most American Congregational Rabbis follow the ruling of Rav Moshe Feinstein and do not kasher plastic.

cRc Policies

1. Are plastic and other synthetic materials suitable for kashering with hag’alah, or should it be given the same status as cheress?

They may be kashered with hag’alah, subject to the concerns of דלמא חייס עלייהו שמא פקעי (discussed below in Chapter 3).

If one purchases pots or dishes from a stored owned by a non-Jew, he may assume that those items are brand-new and were never used, such that they can be used without kashering. [They do require tevillas keilim.] If, however, one purchases these types of items from a private person (e.g., on eBay), they should assume it had previously been used, and therefore kashering is required. We will discuss two types of “new pots” where the halacha is somewhat more complicated: Farberware pots and pre-seasoned cast iron pots.

In the 1980s, Rav Belsky spent time in a Farberware pot factory to see if there was basis to the persistent rumors that those pots were shined by smearing lard onto them. He found that lubricant used in the early stages do not pose a concern because the pots are subsequently kashered as part of their processing. A different lubricant during the buffing of the pots, and there is no kashering performed afterwards. Nonetheless, Rav Belsky said that the pots may be used because the lubricant is inedible, no b’lios penetrate the pot, and even if they did the b’lios would be batel into the food.

Cast iron pots and pans must be “seasoned” to prevent rusting and to give them non-stick properties. Seasoning is accomplished by coating the pot with oil or fat and then putting them in a hot or warm oven for a few hours. If a pot is seasoned at the factory, then there is a potential that non-kosher oil or fat was used which would render the pot non-kosher.

Rav Schwartz zt”l ruled that new cast iron cookware does not have to be cleaned before kashering. He reasoned that although the seasoning can be removed with soap, it is considered “absorbed” (rather than tangible) since the surface of the cookware exhibits no trace of the oil/seasoning. The absorbed ta’am can be removed through hag’alah or libun kal (see below). Although there is one opinion in Rishonim that these pots must be kashered through libun gamur [since the non-kosher oil had direct contact with the pot in the fire], the consensus is that hag’alah suffices since the oil was in a liquid state when it was heated.

Note: Hag’alah and libun kal are only appropriate when kashering to remove the non-kosher seasoning applied in the factory. But if one mistakenly uses cast iron cookware with a non-kosher item, the rationale noted above will often not apply, and libun gamur will oftentimes be required.

Hag’alah involves bringing a pot of water to a boil and submerging the cast iron pot into it. Hag’alah can be performed “piecemeal”, such that if a cast iron skillet is very large there is no need to submerge the entire skillet into the pot simultaneously. Additionally, cast iron cookware tends to be heavy and thick, so it should be left in the hag’alah water for long enough that the water comes back to a boil which indicates that the cast iron itself has become heated to hag’alah temperatures.

Libun kal for a cast iron pot can be accomplished either by putting it into an oven or by placing it face down over a stovetop flame. It should remain in the oven or over the flame until the “other/outer” side of the pot is hotter than 175° F (yad soledes bo, l’chumrah).

cRc Policies

1. If one purchases pots from a store, may he assume that they were never used (and are therefore excused from kashering)?

Yes

2. If one purchases pots from an individual on eBay and that person claims that the pots were never used, may he accept this claim and therefore not kasher the pots?

No

3. Based on the information presented in the chapter, is one required to kasher new Farberware pots before using them?

No

4. If one purchases a brand new, pre-seasoned, cast-iron skillet, must it be kashered before use?

Yes

5. Assuming the answer to the previous question is “yes”:

a. Must one wash off the seasoning before beginning the hot kashering?

No

b. Should the skillet be kashered with hag’alah or libun?

Hag’alah

6. When one performs hag’alah to a very large utensil, such as a skillet:

a. Is it acceptable to kasher one side at a time?

Yes

b. Is it acceptable to just submerge the skillet into the boiling water momentarily?

No, it must remain in the water until the fire causes the water to boil again, as this will ensure that the utensil was thoroughly heated (and kashered)

7. Under what circumstances may one accept a company’s claim that the oil they use for seasoning cast-iron skillets, is kosher?

Never, unless there is some element of independent confirmation (i.e. hashgachah)

Libun is an effective method of kashering cheress, but in practice one may not kasher this way due to a Rabbinic concern that the kashering will not be performed properly. The person will be apprehensive that leaving the coals in for long enough will crack the cheress, and he might therefore remove the coals too early. Shulchan Aruch says that the only way to perform libun is to put the utensils into a kiln which demonstrates that the person is not afraid of ruining the utensil. This concern is referred to as “דלמא חייס עלייהו שמא פקעי”.

Shulchan Aruch notes the concern of שמא פקעי as relates to performing libun gamur, but there are times when the same issue arises for someone performing libun kal or hag’alah. An example where this is relevant for libun kal is when attempting to kasher a glass stovetop; in theory, it could be kashered with by passing a torch over the surface but doing so might crack the glass and therefore it may not be done.

Another example of שמא פקעי is when kashering a tank used to store cold liquids, as those tanks are often unable to withstand kashering with boiling water. [They will not break from the hot water but rather may “collapse” during the post-hag’alah cooling]. An inexperienced person kashering this type of tank will be concerned that he will break the tank, and therefore may not perform hag’alah.

A different concern applies when equipment undergoes “pegimah” with hot caustic. A company will be nervous to allow the use of caustic in an open vessel because hot caustic poses a significant safety concern if it accidentally comes in contact with someone’s skin. In cases where that is a concern, it would be forbidden to perform pegimah. [This concern does not apply when performing pegimah on a closed system, such as a plate heat exchanger].

What if a company signs a release form for the kashering? Does that remove any concerns that they will not allow the Mashgiach to do the full kashering? Some argue that Chazal forbade kashering whenever there is a concern of חייס עלייהו שמא פקעי and signing a paper does not change anything. On the other hand, the fact that Rishonim allow libun in a kiln (even though the Gemara just says that libun raises concerns of חייס עליה), indicates that kashering is permitted anytime the owner demonstrates that he is not concerned. It would therefore appear that if a company’s engineering or sanitation personnel approve a kashering protocol and are willing to sign a release form, that suffices to allow the kashering to proceed.

cRc Policies

1. May a consumer kasher a glass stovetop by passing a torch over the surface?

No

2. If a tank is built with very thin walls because it is only intended to hold cold liquids, may it be kashered by pouring boiling water on its (interior) surfaces?

No

[The following question assumes it is proper and acceptable to be “pogem” equipment to avoid the need for it to be aino ben yomo; see Chapter 64].

3. May one be pogem with hot caustic…

a. In an open tank?

No

b. In a closed heat exchanger?

Yes

4. A piece of equipment requires a form of kashering where there is a legitimate concern of חייס עלייהו שמא פקעי, but the company created and approved the proposed procedure and signed a release form to allow the kashering. May the Mashgiach perform the kashering?

Yes, assuming the Mashgiach is also not concerned that kashering will break the utensil

There are specific limited situations where a cheress utensil can be kashered with three hag’alos instead of libun. Specifically, it is allowed when the only non-kosher item was an issur d’rabannan which is אין לו עיקר מן התורה, of which we have two examples: challas chutz la’aretz and bishul akum.

– —

If someone has a non-kosher utensil which has not been kashered, they may not use it with any food even if the food is cold. Although cold food will not draw out any of the non-kosher ta’am, there is a concern that if they use it for cold they might forget and use it with hot food. In Yoreh Deah, Rema adds that this Rabbinic prohibition is limited to “regular” use, but one can occasionally use a clean, non-kosher dish for cold kosher use. For example, if someone is in a non-kosher hotel, they can drink cold water out of the hotel’s non-kosher glasses; visiting a hotel is considered an “occasional” use, and therefore cold water can be put into the glass even though the cup is not kosher.

Accordingly, kosher caterers may set the tables at a kosher event with the non-kosher drinking glasses from a non-kosher hotel. Those glasses may be non-kosher, but we view a kosher event at the hotel as “occasional”, and therefore allow the cups to be used with cold. But the caterer cannot use his own drinking glasses for both meat and dairy. Since those glasses belong to him, their use is considered “regular” and therefore forbidden.

Two reasons have been suggested to not allow caterers to use hotel glasses: Firstly, if the caterer hosts events on a regular basis, the use of hotel glasses should be considered “regular” since the caterer is doing it all the time (Rav Schachter). Secondly, it can be argued that a caterer cannot claim this use is “occasional” if he planned an event based on this intended use (Rav Fuerst). Despite these points, it is common practice to allow kosher caterers to use non-kosher hotel glasses for cold beverages.

Should the prohibition against using non-kosher utensils on a regular basis apply to companies owned by non-Jews? Can the hashgachah allow them to use non-kosher equipment to produce a cold item which will be certified as kosher? Iggeros Moshe says that it is repulsive (מכוער הדבר) for a certifying agency to allow a non-Jewish company to do something that would be forbidden if the same thing was done by a Shomer Shabbos. That would seemingly be a reason to not allow the non-Jewish company to use their non-kosher equipment for cold products. Nonetheless, although hashgachos generally take a strict approach when questions arise regarding the “מכוער הדבר” principle, it appears that as relates to this specific issue most are lenient for companies owned by non-Jews.

cRc Policies

1. 1. If someone is at a non-kosher hotel, can he use the non-kosher glasses to drink water at ambient temperature?

Yes

2. May a kosher caterer use the same glasses for both meat and dairy?

No

3. A kosher event will be held at a non-kosher hotel. May the kosher caterer set the tables using the hotel’s non-kosher glasses?

Yes, if the non-kosher hotel is not used by the kosher caterer on a frequent and regular basis.

4. A company owned by non-Jews has equipment which was used to process hot, non-kosher materials. Can they use that equipment to produce certified kosher products, if the kosher production will not involve any heat?

Yes, but it is preferable to avoid this.

All agree that when performing libun to a kli cheress, the fire must come from the side where the chametz or treif food was, rather than from the side where the fire was during cooking. Pri Megadim says that the same applies if the utensil metal, but Avnei Nezer argues that when libun gamur performed to metal the entire utensil becomes like “a piece of fire” and it is therefore inconsequential where the flame is. This leniency is limited to libun gamur and does not apply when one kashers with libun kal. Therefore, in cases where it is appropriate to kasher a blech, hot plate, or pan with libun kal, they should be put upside down on the stovetop (i.e., with the food-side facing the fire).

It is not possible to turn a glass stovetop upside down, and at first glance it would seem that just turning on the electric coils – which are underneath the glass – would run afoul of the requirement that the flame be on the side where the food was. However, since the surface is just glass [which many Poskim say does not absorb at all], there may be justification for being lenient. It is also possible to use a non-kosher glass stovetop without kashering it, by placing metal discs between the glass and the pots. No ta’am can possibly transfer between the glass stovetop and the kosher pot, and the food in the pot will be unaffected by the stovetop’s status.

The requirement that the heat come from the side where the food was, also applies when performing hag’alah. In a home setting this means that to kasher the upper portion (i.e., cover) of a kedairah blech, it should be turned upside down and placed – part at a time – into the lower portion (i.e., water-pan) which is filled with boiling water. In this way, the boiling hag’alah water will have contact with the food-side of the cover and effect a proper hag’alah. In a commercial setting this halacha would be relevant to certain types of reactors or kettles; for more on that see https://kshr.us/Sappirim31.

cRc Policies

1. Must the fire (or boiling water) be on the side which had the food-contact when kashering….

a. With libun gamur on cheress?

Yes

b. With libun gamur on metal?

No

c. With libun kal on metal?

Yes

d. With libun kal on glass?

Yes

e. With hag’alah?

Yes

2. If one was kashering a blech, hot plate, cast iron pan, or frying pan with libun kal by placing them over a fire for a given amount of time, can the kashering be performed when they are “right side up” or must they be turned upside down?

Upside down

3. Can libun kal be performed on a glass stovetop, by merely turning on the electric coils until the glass reaches the desired temperature?

Yes. This is based on a tziruf of different opinions regarding kashering from the “wrong” side and the status of glass.

An alternative is to not kasher the stovetop and instead place all pots onto metal discs so that the pots have no contact with the stovetop.

4. In a home-oven whose flames are not in the cooking chamber, may libun kal be accomplished by turning on the flames until the chamber reaches the desired temperature?

Yes

5. If one was kashering a kedairah blech with hag’alah, does the boiling water have to come in contact with the top of the cover (the part which touches the pots and food) or is sufficient if the underside of the pan has that contact?

The top of the cover

A heat exchanger is a machine which allows liquids to be heated or cooled via indirect contact with the heating or cooling media. A plate heat exchanger is made of dozens of identical, thin, rutted, stainless steel plates (shown in the pictures) with dozens of these plates sandwiched together to create the complete heat exchanger. The product and heating media flow in the thin space between one plate and the next, as follows:

• Product flows between plates 1 and 2, 3 and 4, 5 and 6 etc.

• Media flows between plates 2 and 3, 4 and 5, 6 and 7 etc.

Accordingly, each plate has product on one side and media on the other. As the product and media flow through their respective areas, the heating media transfers its heat through the plate into the product. To see a visualization of how this works, see the video at https://bit.ly/3rAgGR2, starting at about 5 minutes in.

Heat exchangers can be kashered relatively easily by draining all heating/cooling media, cleaning the heat exchanger thoroughly, waiting 24 hours, and then heating fresh water to hag’alah levels in the heat exchanger.

The simple heat exchanger described above has just one function – heating product – and the product makes just one pass through the heat exchanger. A heat exchanger with regeneration is considerably more sophisticated; it typically has two different functions – heating and cooling – and usually has 4 separate sections to accomplish those functions. For example, orange juice might enter the regeneration section (described below) at 40° F where it is heated to 120° F; move to the heating section where it reaches 165° F; pass through holding tubes out of the heat exchanger; return to the other side of the regeneration section, where it cools to 80° F; and then pass through 2 cooling sections which bring it to the storage and bottling temperature of 40° F.

Aside from having both heating and cooling capabilities, the heart of the system is the regeneration section, known colloquially as the “regen”, which operates as follows: Instead of having steam or hot water serve as the heating media, the cold, incoming orange juice on one side of the heat exchanger plates is heated by hot, already-pasteurized orange juice flowing on the “other” side of the plates! This efficiently serves the dual function of heating the incoming juice while simultaneously cooling the outgoing juice.

The setup of a typical heat exchanger with regeneration is shown in the accompanying diagram. In the simplified diagram, a colored line shows the product starting (cold) in the regeneration section, moving to the heating section, out of the heat exchanger to the holding tubes, and then back (hot) to the “other side” of the regeneration section, and finally to the two cooling sections of the heat exchanger. [Heating and cooling media are not shown].

After the product leaves the holding tubes its temperature is measured to ascertain whether the minimum pasteurization temperature was met. If the product is at the required temperature, it continues to flow as described above and is said to be in “forward flow”. But if the temperature is too low, the product is diverted to the balance tank so it can be pasteurized once again; in such cases, the product is said to be in “divert flow”.

In establishing a kashering protocol, one must consider the following:

• There is a range of temperature in the heat exchanger, with about half of it being above yad soledes bo. The letter of the law is that hag’alah requires water which is just above the production temperature (i.e., k’bol’oh kach polto), but l’chatchilah one should always kasher at roschin.

• The hag’alah water must contact the utensil from the side which had contact with the non-kosher food. This is relevant in the regeneration section where the non-kosher food was itself the heating media, such that hag’alah water must pass on both sides of the plates.

• Due to “divert”, the balance tank, first parts of the regen section, and piping to and from the heat exchanger will occasionally have contact with non-kosher product and must be kashered appropriately. [Some of these might not be included in the company’s own sterilization procedures].

cRc Policies

1. How should a simple heat exchanger be kashered?

Clean it thoroughly, drain all heating media, wait 24 hours, heat fresh water to hag’alah levels in the heat exchanger, and allow it to circulate for 5-10 minutes.

2. Should hag’alah be performed with water that is a few degrees above production temperature (כבולעו כך פולטו) or with water that it roschin?

Wherever possible, the water should be roschin (or at least a temperature that qualifies as roschin, see Chapter 10), but where that is not possible then a few degrees over production temperature suffices.

3. How should one kasher a heat exchanger which has regeneration?

First, (1) drain the heating media, (2) turn off the pumps which control the cooling media, (3) fill the balance tank with water, set the heat exchanger’s set-point for 212° F, and being flow of water, (4) manually put the system into divert flow, (5) maintain this flow until the red/hot pencil indicates that the water is at 212° F for a few minutes. Then (6) switch the system into forward flow, and (7) have the water flow from the finished product tank back to the balance tank and maintain this flow for a few minutes.

4. If it is expensive or logistically difficult to have a Mashgiach present for kashering, is it acceptable to approve a kashering based on monitoring of charts and similar technological means?

Yes, assuming the charts are automated and reliable.

The charts etc. will show that the kashering protocol was followed, and this should be supplemented with (a) the company’s schedule and handwritten logs which indicate that kosher product was only produced after the kashering, (b) unannounced Mashgiach visits to ensure kosher and non-kosher are produced at the “right” times and with the appropriate ingredients, and (c) occasionally the Mashgiach should be present for a kashering to verify that the protocol is appropriate.

If a utensil was used with cold non-kosher food, the utensil can be used without a hot kashering after a thorough cleaning. An exception to that rule is that a knife used to cut cold food needs to be cleaned with a more thorough method called, “ne’itzah”. Ne’itzah involves thrusting the knife’s blade into relatively hard (tightly packed) dirt 10 times (each time in a different spot) to remove the film of residue which might remain on the knife.

But there are some cases where ne’itzah is physically impossible. For example, blocks of cheese are sliced with cheese wires where the cheese is forced through stationary wires and those wires cut through the cheese, or potatoes are forced through stationary blades to create French fries. The wires and blades are functioning as knives but there is no way to perform a traditional ne’itzah to them. Instead, they are cleaned/kashered by scrubbing them with steel wool which is seen as a “reverse” ne’itzah; rather than push the knife into the abrasive soil (ne’itzah), the abrasive material (steel wool) is pushed/scrubbed over the knife and gets it just as clean.

cRc Policies

1. Does the minhag to have designated knives for Pesach (rather than kasher the year-round knives) apply nowadays?

No

2. Cheese wires were used to slice non-kosher cheese. Can the wires be used for kosher cheese if they are cleaned thoroughly and scrubbed with steel wool?

Yes

3. If a knife will be kashered with hag’alah, must it undergo נעיצה beforehand?

No

Magen Avraham records a custom not to kasher from dairy to meat (or vice versa). He explains that this is out of concern that if people could have just one set of pots for both meat and dairy (and kasher back and forth), there would be times when they would forget the pot’s status and mistakenly use it for dairy when it was it was actually fleishig (or vice versa). Accordingly, a custom developed to never kasher between meat and dairy, so that people would be forced to have two sets of pots etc., and they would therefore avoid these types of mistakes in the kitchen.

Some exceptions to this minhag are that it does not apply when someone kashers a utensil for Pesach or after it became treif, or if someone mistakenly used a pareve knife to cut hot meat (for example). The goal – that people have two sets of dishes – is not affected by these unusual situations, and therefore are not included in the minhag.

There are strong inferences that Magen Avraham and others would say that the minhag applies whether the person is kashering via hag’alah or libun kal. However, Maharsham suggests that it is limited to hag’alah but one may kasher with libun kal between meat and dairy.

Some say that the minhag also restricts kashering from meat or dairy to pareve. If so, why is it a regular practice that certified companies kasher their equipment from dairy to pareve? Some argue that minhagim, such as this, do not apply to non-Jews in which case the question is limited to companies owned by Jewish people. An alternate answer may be that the minhag does not apply when there is someone (a Mashgiach) assigned to ensure that pareve product is never produced when the equipment is dairy. His oversight role suffices to permit the equipment to be kashered on a regular basis.

cRc Policies

1. Do the kashering leniencies associated with heter, apply to kosher meat and kosher milk (not mixed together)?

Yes

2. Is there a minhag not to kasher between meat and dairy?

Yes

3. Assuming the answer to the previous question is “yes”, does the minhag apply in the following cases?

a. If the utensil is being kashered from chametz (for Pesach) or from non-kosher?

No

b. If a utensil was mistakenly used incorrectly (e.g. a pareve knife was used to cut hot meat)?

No

c. If the kashering will be performed using libun kal?

Yes

d. If the kashering will be performed using libun gamur?

No

e. If the kashering will be performed using ne’itzah?

No

f. If the kashering is between dairy (or meat) and pareve?

No

g. In a factory which is certified as kosher?

No