Kashrut for Pesach

Section I: Why

In typical Jewish style, there are many answers to ‘Why keep kosher for Pesach?' None excludes the others. Here are three:

• Payback time. The obligation to keep kosher at Pesach is just that, an obligation. It is part of what we owe in gratitude for the incredible miracle of our existence, our liberation from slavery and our receiving of Torah. It is a way for us 21st Century Jews to acknowledge the gift of our life as free people, a gift beyond price.

• Spring cleaning. Leaven is fermented; it is part of last year’s harvest. At Pesach we forgo leaven; we use only the new harvest. Pesach is a time to clear out old stock, not only of our cabinets, but our souls. The cleaning of our homes, purging them of hametz so that they are kosher – which is to say, fit – is a way of renewing our souls.

• Liberation and solidarity. There are millions of people around the world who cannot meet their basic needs because of political or economic oppression.  Diminishing our food, even in this limited way, is a way of tapping our collective memory of Egyptian oppression and building solidarity with them.

Of course, beyond these rationales, there is also the simple reality that this is a central part of Jewish civilization and collective memory. Why do we Americans light fireworks on the fourth of July? Sure, there is a story about the rocket’s red glare, and there is the simple reality that that is just part of American culture. So too with regards to kashering for Pesach, some of us remember koshering the house with our families of origin, others want to enter into the collective memory of the Jewish people around this ritual, and others of us want our children to be able to do so. Regardless of why you might do it, here are some thoughts on what you might actually do to kasher.

Section III: Cleaning & making kosher the kitchen & vessels

Many people have entire sections of kitchenware that can be switched over for Pesach. That makes some Pesach preparations easier. However, even if you don’t, it is possible to make many items of kitchenware kosher for Pesach, and even if you have entirely separate pots and pans there is still work to be done on surfaces, ovens, etc.

To kosher a vessel all three of the following procedures need to be followed:

• The vessel must be clean of any markings of its previous use. All marks must be removed. In the case of well-used saucepans, etc. it may not be possible to remove deeply cooked-in stains. These pans cannot be koshered. I would consider it impossible to remove schmutz from joints in a vessel, or between the vessel and its handle. These vessels cannot be kashered.

• The vessel must be left unused for 24 hours after its last use with the ingredient that is to be purged before being koshered. 

• Ingredients that are absorbed into a vessel are secreted and can be purged from the vessel in the same way in which they were originally absorbed. 

The key issues in understanding how an ingredient has been absorbed are the level of heat the vessel has been subjected to and the material of manufacture. Again these processes only apply once the vessel has been cleaned and left for 24 hours.

• A pot that has been used on a stove top, metal kitchen utensils and metal cutlery used for eating hot food can be koshered by being dunked in boiling water. Big pots (as opposed to pans) can be koshered if filled to overflowing with boiling water (so both inside and outside of the vessel are covered by the water); this is usually done by filling a pot with water then dropping a stone in the water causing a small amount of water to flow over the top and down the sides. Fragile vessels of this type that cannot be dunked cannot be koshered. 

• It is very difficult to render plastic ware spotlessly clean and free of any markings of use, but this is necessary if it is to be made kosher by use of boiling water. 

• Metal pans used in the oven are very difficult to clean thoroughly. However, once they are thoroughly cleaned, they can be kashered by heating the pan to an extreme heat for thirty minutes. Ceramic pans cannot be made kosher.

• Ovens, stovetops and grills also need exposure to extreme heat for thirty minutes. Self-cleaning ovens can be cleaned using the self-cleaning function. Other ovens and stoves should be turned on and up to the highest heat and left for 30 minutes. Grills that can be rendered spotlessly clean can be made kosher in a self-cleaning oven or cleaned with high heat for a similar length of time. Again, where it is not possible to clean a grill so it appears clean to the eye, it cannot be made kosher. In these circumstances foil should be used to wrap either the grill or food before it is cooked. 

• Sinks, worktops and tables that come into contact with hot foods or liquids but are not actually used for cooking can be koshered by pouring hot water over a clean surface. A draining rack or large bowl should be used in sinks in which dishes or pots are left to soak. A table that is used for hot foods during the year, but cannot withstand boiling water, should be cleaned and covered at Pesach.

• Ceramics are held by the Rabbis to be so porous that what they have previously absorbed can never be fully purged. Ceramic vessels including plates, mugs, etc. cannot be koshered. 

• Glass is held by the Rabbis to be impervious to absorbing food and, theoretically, does not need to be koshered. In practice it is traditional to soak glassware in water for 24 hours (usually a bath is the best way to do this). Pyrex is a modern material, most authorities consider that it cannot be treated like glass, but I am inclined to treat it as glass when there is no evidence of baked-in coloration on, for example, a baking dish.

• A microwave oven can be made kosher if cleaned and then put on high for 2 minutes with a bowl of water inside. (Ensure the water does not run out or the oven may be damaged.)

• Dishwashers should be put through an entire cycle on the hottest setting before being used to clean vessels for use at Pesach.

• Other items of kitchen machinery present a range of challenges - please contact me with any specific queries. 

One-time-use vessels can be an easy way-out of making a kitchen kosher at Pesach, but they come at an increasingly untenable cost for our planet. Baal tashchit is the halachic principle that prohibits wasting natural resources. Please take whatever steps you can to reduce wastage caused by one-time-use-vessels and in particular please avoid the most ecologically damaging one-time-use-vessels such as those made of polystyrene. 

This guide is based on guides prepared by Rabbis Jeremy Gordon and Joel Roth. We are grateful for their assistance.