Can porcelain or marble countertops be kashered, and if so how? This question comes up regularly when people move into a previously-owned house, or on an annual basis when it is time to kasher the kitchen for Pesach.
This is not a trivial question. I have heard multiple stories of cases where someone has moved into a new house that had non-Jewish or non-observant owners and were instructed by their rabbis that the only way to kasher a marble countertop would be to pour boiling hot water on it straight from the kettle, or to place an iron over a thin layer of water on the countertop’s surface, either one of which would likely crack and damage the countertop’s surface. As a result, people have had to rip out their countertops and replace them with new ones at the cost of tens of thousands of dollars.
And when it comes to Pesach, the only option for someone who is afraid that boiling water will damage their marble countertop is to completely cover it with contact paper or tinfoil.
In the case of a porcelain countertop, the psak that most people hear is that pouring building water (or using an iron!) is not even an option, as porcelain cannot be kashered. Only a countertop fully covered with contact paper or tinfoil will be acceptable.
For many people, even when we are not talking about serious financial loss, such demands can be a serious compromise in what it means to have a beautiful home for the chag, especially when one wants to invite family and friends and feel good about the home into which they will be welcoming their guests.
In my view, these stringent rulings are fundamentally mistaken and can cause unnecessary hardship to Jewish families. Both underlying assumptions—(1) that porcelain cannot be kashered and (2) that countertops even require kashering in the first place—deserve serious reconsideration.
Kashering of Different Materials
Granite and marble
All authorities agree that granite and marble can be kashered (SA, OH 451:8). Thus, when possible, a person should kasher her granite countertop for Pesach. This would be done by pouring boiling water from a kettle over the entire surface. Due to the extra stringencies required for Pesach, some poskim even require, as noted above, that one run an iron over a film of water on top of the countertop (see SA OH 451:6)—an extreme recourse which may cause cracking and other damage, especially in the case of marble surfaces. As a result, kashrut authorities advise people that their only option is to cover the countertops and not place anything directly on their surface.
In my opinion, when it is not possible to kasher a countertop without damage, one can use the countertop without any kashering, provided that the surface is vigorously cleaned to remove any food residue that might be on it, because, stated simply, countertops are not pots. We will return to this after first addressing the question of the kasherability of porcelain countertops altogether.
Porcelain
Porcelain is a type of pottery made from clay and fired in a kiln. As a rule, halakha (Avoda Zara 34a, SAOH 451:1) assumes that pottery vessels (klei cheres) absorb the taste of things that are cooked in them, and that these tastes will remain stuck in the pottery, with no way to extract them. This is based on Lev. 6:21, which dictates that pottery vessels that were used to cook a sin offering sacrifice must be shattered.
Many poskim in the past have applied this principle to porcelain, ruling that it is a pottery vessel that can thus not be kashered.
However, porcelain differs significantly from traditional pottery. It is fired at much higher temperatures and undergoes multiple firings specifically to make it non-porous and non-absorbent. The question then becomes: should porcelain be subject to the same laws as traditional pottery?
Radbaz (Rabbi David ben Solomon ibn Avi Zimra, 1479-1573, born in Spain and later Chief Rabbi of the Jews of Egypt) conducted an experiment to test whether porcelain is absorbent. He weighed a porcelain vessel before use, cooked with it, then weighed it again. Finding that it weighed slightly more after use, he concluded that porcelain is indeed absorbent and must therefore be treated with the same stringency as other pottery.
Nevertheless, a significant number of contemporary authorities disagree. They argue that modern porcelain does not follow the Talmudic laws of pottery for the simple reason that unlike pottery, it doesn’t absorb moisture! Porcelain is made from highly refined clay and minerals, pressed tightly and fired at extremely high temperatures (a process called vitrification), all specifically to make it non-absorbent and resistant to stains. Many porcelain products are also often glazed, which adds another non-porous, impervious layer of glass to the surface.
The question of how we treat porcelain boils down to whether a posek adopts a formalist or realist approach when it comes to categorizing for kashrut purposes new materials not addressed in the Talmud. A formalist approach would simply state that since porcelain is made of the same material as pottery, and since pottery is defined in the Talmud as absorbent and not kasherable, the same would be true of porcelain. A realist approach, by contrast, would ask whether porcelain is in fact absorbent or not.
Already in the Talmud (Pesachim 30b), when discussing how to categorize different types of pottery vessels, the Rabbis based their determinations on an empirical assessment of whether liquids actually absorb in these materials and not on a formalistic, categorical approach. Similarly, Radbaz, in basing his ruling on the experiment that he conducted, made clear that it is the practical reality of absorption that matters.
While Radbaz concluded from his experiments that the porcelain he was using was absorbent, that is not the reality with porcelain nowadays. In Radbaz’s time, the coating used for porcelain was often imperfect and contained cracks, and the manufacturing process was less rigorous than it is today. Thanks to advancements in manufacturing technology and industry standards, porcelain manufactured today is, by contrast, completely non-absorbent.
Following this, not only would it be possible according to halakha to kasher modern porcelain, but kashering may not even be necessary because these materials are entirely non-absorbent. This position is adopted by a number of poskim, including the author of the Knesset HaGedolah (R. Chaim Benveniste, 1603-1673) who writes that the widespread practice was to use the same porcelain vessels—provided they had no cracks in the glazed—for meat and milk, for chametz and year-round, and even to repurpose non-kosher ones, without any kashering required. While he himself did use different dishes for Pesach, he regarded this as a personal stringency, and believed that as a matter of halakha, no kashering is required (Shiyarei K’nesset HaGedolah on Beit Yosef OH 451 no. 30; cf. Peninei Halakha, Laws of Pesach, 11.11).
Despite the fact that the lenient position is the most logical one, there is no question that the widespread practice remains to be strict regarding porcelain, following the position adopted by many poskim—depsite the fact that their porcelain was likely different than ours. This is certainly the li’chatchila position that we should adopt year-round, and even more so when it comes to Pesach, when we are generally more strict in matters of kashering than we are year-round (see SA OH 451:6).
However, when the question is one not of pots and pans, but of countertops, there is an additional strong reason to be lenient, beyond the question of the absorbancy and kasherability of porcelain.
Must Countertops Be Kashered?
As a matter of strict halakha, countertops that have absorbed non-kosher tastes may not require kashering at all. In general, the halakha is that if a person cooked in a pot that was used to cook non-kosher food over 24 hours ago (an eino ben yomo), the food that was cooked now is nonetheless kosher. This is based on the principle that after 24 hours any taste of non-kosher food transferring from the pot to the food will make the food being cooked taste worse (notein taam lifgam), and therefore of no halakhic significance.
Despite this, the Rabbis prohibited the use of such a day-old pot lest one come to use it when it is less than a day old, in which case it would make the food cooked in it forbidden. This is why we have to kasher non-kosher pots and pans even after we have waited 24 hours from their last use (Avoda Zara 76a, SA YD 122:2).
Countertops, however, are fundamentally different from pots, and for one simple reason: we do not cook food on them! They are used, rather, as a place on which to set other things such as pots, plates, (cold) food, etc. A countertop never, under normal use, comes in direct contact with boiling hot (yad soledet bo) food. Even if a pot is put on it immediately after being removed from the fire, no taste will transfer from the pot to the surface of the countertop, based on the principle that eyn balua yotzei me’chaticha li’chaticha b’lo rotev—taste does not transfer between two solid non-food items, such as a countertop and a pot, unless there is hot liquid between them.
The only way that, under normal use, the taste of food can transfer to the countertop is if an accident occurs—that is, when there is spillage directly from a pot onto the countertop while the food is still boiling hot.
As such, the use of countertops would never have been part of the rabbinic requirement of kashering to begin with! When it comes to a pot, one can say that it can’t be used (i.e., to cook something in it), even if it has been more than 24 hours since last use, because it might be used (i.e., to cook something in it) within the first 24 hours. When it comes to a countertop, however, it makes no sense to say that it can’t be used (i.e., to place something on it), even if it’s been more than 24 hours since last accidental spillage, because it might be used (i.e., to put something on it) within 24 hours of last accidental spillage! Using it within 24 hours – placing things on it – is not a problem!
In short, the rabbis did not forbid use of something lest an accident would occur. They only forbade normal use, such as cooking, which transfers taste, lest such normal use would transfer taste when the taste was still forbidden. This is completely irrelevant to the use of a countertop.
What arises from this is that once it has been 24 hours since the last time hot food has come directly in contact with the countertop, one may use it li’chatchilah with any other kind of food because it falls entirely outside the requirement to be kashered.
Even were one to disagree with the above, and put countertops in the same category as pots, no kashering would be needed after 24 hours for another reason. The laws of kashering are based on the item’s standard use. If something is generally used directly on the fire, then it has to be kashered directly on the fire. If it is generally used, like a soup tureen, by having hot liquid poured into it, then it can likewise be kashered by pouring hot liquid into it. And—most importantly—if it is generally used in a way such that taste doesn’t transfer, then it doesn’t require kashering at all.
When it comes to Pesach, we are generally stricter and require that one kasher something based on its less common use (see Rema, SA OH 451:6). Spillage, however, is not a “less common” use—it is an accident, not an intentional use at all, and thus one might logically conclude that it would fall outside this stringency. Nevertheless, Shulkhan Arukh (OH 451:20) explicitly states that when it comes to tables, even though hot food is never intentionally placed directly on them, the practice is still to kasher them for Pesach by pouring boiling water on them. This is out of a concern that there might have been some accidental spillage of hot chametz at some earlier point during the year. This is a specific Pesach stringency, as the standard halakha, as we have seen, is that kashering follows the normal use of the vessel.
Conclusion
For year-round use, such as when renting an Airbnb or buying a house that has had previous owners, then, once it is 24 hours from the last time it came in direct contact with hot food:
- For marble countertops that will be damaged with kashering, one should clean the surface thoroughly—ideally with a cleanser that will not only remove any film or food residue, but will also make it inedible. No additional kashering is required.
- Porcelain countertops and other countertops about which there is no concern for damage should be kashered by pouring boiling water on them from a kettle.
The reason that no kashering is required in the case of marble countertops is that, as laid out above, a strong argument can be made that countertops fall totally outside of the rabbinic requirement to kasher cookware once more than 24 hours has transpired. Furthermore, normal kashering follows the regular use of the item being kashered, which in this case is use that transfers no taste.
When it comes to porcelain countertops, where kashering can be done without concern for damage to the countertop, then when dealing with one’s own home, one should follow the general practice and kasher them as normal. As we have seen, against the general approach that porcelain cannot be kashered at all, it is quite possible—indeed, likely—that it can be kashered or that it might not require kashering altogether. The need to kasher at all in this case comes out of deference to common practice. In the case of a short-term rental, such as an Airbnb or the like, one need not kasher the countertops at all if it presents any difficulty..
For Pesach, because of the standard stringency to kasher based even on non-regular use, including for items like tables where the only concern is accidental spillage:
- One should kasher or cover countertops when this is possible and will not be a hardship.
- In cases where kashering would damage the countertop, and it would be felt as a hardship to make their countertops ugly by covering them at a time when one wants them to look particularly beautiful, there is room to be lenient and not require kashering. It is sufficient for a person to clean the countertop surface well with a cleansing agent that would render any food residue inedible. Although there is a general practice to kasher tables, this is a stringency that goes well beyond what would normally be required and in a case of hardship or difficulty, it is sufficient to follow standard halakha and forgo this step.
It is my tefillah that we are able give proper attention to all of the demands and stringencies of Pesach and, at the same time, to celebrate it with true joy and simchat ha’chag. May it truly be a chag of freedom and rejoicing for us all.
Daf of the Day
