Baltimore, MD - Mar. 27, 2023 - Reposted upon request:
Baltimore, MD - Mar. 26, 2022 - Kashering is certainly one of the most critical aspects of preparation for Pesach. To many, the process may seem daunting for a variety of reasons: It is not something people do regularly, there are serious safety risks involved in handling hot items and boiling water, and potential to damage the kitchen. Also, if not accomplished correctly, there is a risk that after all the work is done, with hot water running all over the place, the kitchen may not actually be really kosher for Pesach!
However, it really does not need to be that difficult and with a little know-how and effort, most people can be capable of kashering their kitchen. For a full step-by-step guide to proper kashering procedures, consult the STAR-K Passover Guide, which is available in hard copy and in digital format. Video tutorials are available here and here.
This brief article will focus on proper (as well as improper) methods of kashering countertops made from granite or other stone materials.
Countertops that are made of solid stone, like Pure Granite, Quartzite, or Marble, can be kashered. Other types of synthetic or composite materials (including Silestone, Porcelain Enamel, Corian, Quartz, Formica, and Granite Composite) cannot be kashered and should instead be covered.
Solid stone countertops are kashered through Iruy Roschin, which means pouring boiling water from a pot that has been heated on a fire. Actual water is needed to kasher, not steam. Many people have been looking to use steam machines and similar devices for kashering purposes. Using a steam machine is effective only when it boils and sprays actual water. If it produces only steam, even if the steam exits the nozzle at 212°F or above, that is not considered kashering. STAR-K has tested many models of steamers available commercially and have found that almost all of them will only produce hot steam and not boiling water.
There is a way of using a steam machine to kasher countertops in an acceptable manner, but it requires a degree of patience and diligence. Steam can be sprayed on the surface, which then condenses into water. Subsequently, the steamer can heat those water droplets until they boil. However, this method takes a considerable amount of time to cover each area of the surface and greatly limits its practical usefulness.
Another technique to kasher stone countertops involves the concept of Even Meluban. A small amount of [hot] water is sprayed or poured onto the counter and then one goes over the water with a hot iron, or heated cast-iron plate (held firmly by tongs or other means), which boils the water upon contact. For this to work, the hot iron or plate must be hot enough to boil the water on contact and also maintain its heat throughout the process. This method is highly effective and efficient however, due to the inherent danger involved it should only be performed by competent individuals who have the requisite expertise to do this properly and effectively.
Of course, there’s nothing wrong with the traditional method of covering your counters, like in the good ol’ days before stone became popular.
The STAR-K hotline is available to answer your questions. Call us at 410-484-4110 between 9 a.m. and 5 p.m. M-TH, and until 2 p.m. on Friday. You can also send an email to firstname.lastname@example.org.
Wishing everyone a Chag Kasher V’Sameach.
 Metal and wood with a smooth surface can also be kashered.
 See Shulchan Aruch O.Ch. 451:5
 Ibid. 452:5; see Igros Moshe Y.D. 1:60