Kashering a Kitchen Sink

A sink absorbs from what is washed in it, and unlike most earthenware, a ceramic sink can be kashered. That surprises people who know that earthenware generally cannot be, and it is worth knowing before you assume yours has to be replaced or covered.

A ceramic or porcelain sink

The sink where vessels, pots and plates are washed may be kashered even though it is ceramic. The procedure:

1. Scrub and clean it thoroughly, getting into every hole and crack.
2. Clean the join between the sink and the worktop or surrounding tile. This is the part people skip, and it is where residue actually sits.
3. Dry it.
4. Pour boiling water over it from a kli rishon — the vessel the water boiled in, poured directly.

After that it may be used.

A stainless steel or metal sink

The same shape of procedure, and the same emphasis on where to clean. Clean every hole and crack, and then kasher by pouring from a kli rishon that is on the fire — that detail matters, since the water needs to be at full heat as it is poured.

Why the cleaning is the real work

Notice how much of both procedures is cleaning rather than kashering. That is not incidental.

Kashering removes taste absorbed into the material. It does nothing about food sitting on the surface, and anything still there when you pour is simply being cooked onto a clean sink. A sink has more places for residue to hide than almost anything else in a kitchen — the overflow, the plughole surround, the seal where it meets the worktop, the underside of the rim.

Before you start

The usual conditions apply and are covered elsewhere: leave it unused for twenty-four hours first, and understand what standard of cleaning is required.

Sinks vary, and a damaged or heavily crazed surface is a different question from a sound one. Ask your rav about yours.

See also kashering countertops, which is the surface immediately next to it.