Q. We are planning to redo our kitchen. We would like to install counter tops that can easily be kashered for Pesach. Is that possible, or do counter tops of any material need covering for Pesach? If it is possible, what types are easier to kasher? A friend mentioned that some types of granite can be kashered. How does one know which types are acceptable and the best ways to kasher them?
A. Tur (O.C. 451) quotes three different opinions in regards to koshering stoneware. Most lenient is Rav Yitzchok M'simporno who considers rinsing (shtifa) sufficient to render stone utensils kosher for Pesach. On the other extreme, Tur quotes Rav Hai Gaon who maintains that stoneware is similar to ceramics and earthenware. In order to kasher and eliminate any chometz absorbed, they would have to be fired again at the high temperature of a kiln. Tur rules according to the intermediate Rif's opinion. He opines they can be made kosher as other utensils by using regular heat.
In principle, an uncoated slab of granite whose surface is free of irregularities, roughness and is totally polished and smooth can indeed be koshered, by scrubbing clean and then pouring boiling water over it from a connected kettle, (After not using it for twenty-four hours).
The CRC (crcweb.org) provides a list of different counter top materials and what they consider the way to kosher them.
Horav Shlomo Miller's opinion is that in practice, most commercially available stoneware counter tops may not be single slabs but rather composites and they are usually coated. The proper way to use them is by having them scrubbed clean and then totally covered.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit"a
Important Numbers
