My Pesach Plans Were Shattered

This article is brought to you by the editorial team of JLI’s Living Jewish series, which has recently released The Complete Guide to Keeping Kosher as previously reported on COLlive. 

My Pesach plans were ruined when I found out I couldn’t kasher my stovetop. Why are newer NYC apartment appliances more difficult to kasher for Pesach?

Having just moved into a sleek new apartment in a modern condo building, I was ready to roll up my sleeves and make my first Pesach. After mapping out my plan of attack, I sat down with a Pesach kashering guide and discovered the bad news: my beautiful glass-top induction stovetop can’t be kashered.

Why can’t glass be kashered, and is there any solution?

Welcome to the club. As induction ranges replace gas and traditional electric coils across New York’s newer buildings, a growing number of people are running into the same wall. To understand why, we need to know how halachah classifies materials.

Why does the material matter?

Kashering works on the principle of kebole’o kach polto: A utensil expels absorbed flavor the same way it absorbed it. A pot used with boiling liquid is kashered by boiling. A grill used with direct fire is kashered with fire. But utensils that absorb and can’t expel can’t be kashered at all. Earthenware is the classic example: it’s porous enough to absorb taste, but boiling can’t fully drive taste out, and the heat from fire would destroy the utensil.

So where does glass fit in?

The Gemara never addresses kashering glass directly. However, discussions on other halachic topics offer insights into glass’s status with regard to absorptions, and from these, three approaches emerge among the poskim.

The first view holds that glass is smooth and nonporous, so it never absorbs anything in the first place. According to this opinion, glass utensils don’t need kashering at all, even after contact with hot nonkosher food.

The second view treats glass like earthenware. Just as earthenware absorbs but can’t release what it takes in, glass can’t be kashered either.

The third view classifies glass alongside metal: it absorbs, but that absorption can be expunged through kashering.

What’s the ruling?

The Shulchan Aruch follows the first, lenient opinion: Glass doesn’t absorb, so it doesn’t need kashering. The Rama records the Ashkenazic custom to be strict, treating glass as unable to be kashered.

What drives the Rama’s stringency? Some later authorities understand him as likening glass to earthenware: It absorbs and can never release what it takes in. Others argue that the Rama may accept in principle that glass can be kashered like metal, but rules strictly for a practical reason: glass is fragile, and people may not heat the kashering water to the proper boiling temperature for fear of cracking the utensil.

Practically, the Ashkenazic custom is to avoid kashering glass. However, some say this custom applies only to Pesach; for non-Pesach kashering, one may kasher glass.

Back to my stovetop

And that’s the problem with the glass-top stove. The glass surface sits directly over the heating element, and pots cook while in contact with it. Any food that spills or splatters onto the surface during the year gets heated right into the glass. Come Pesach, you’re looking at a surface that, under Ashkenazic practice, cannot be kashered.

Is there any work-around?

Some people cover the glass surface with a metal sheet or a specially designed stovetop cover, creating a barrier between the glass and their Pesach pots. Whether this works depends on both the specific setup and which rabbi you ask. Others skip the built-in stovetop entirely and switch to a portable burner for the week.

So if you’re already staring down a glass cooktop with Pesach around the corner, not to mention any other kashering dilemma you may face, consult a competent rabbi.

The first volume of Living Jewish, The Complete Guide to Keeping Kosher, is available now at Hamafitz and Judaica World.