How to Kasher a Microwave: A Step-by-Step Guide for a Kosher Kitchen

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So you want to start following a kosher lifestyle but your microwave has been used to cook non-kosher foods. Not to worry! “Kashering” your microwave is a straightforward process that will remove any traces of non-kosher food, making your microwave ready for kosher cooking once again.

What Does It Mean to Kasher Something?

“Kashering” is the process of making something kosher after it has come into contact with non-kosher foods. The basis of kashering is that intense heat can purge absorbed particles from kitchen items like pots, pans, and yes – even microwaves.

The process varies depending on the material of the item:

  • Metal items like pots and sinks are kashered by boiling water poured over the surface. The boiling hot water essentially “burns” away any absorbed particles.
  • Glass, porcelain, and plastic cannot be kashered with heat. These must be thoroughly cleaned and left unused for at least 24 hours.
  • Microwaves are kashered through a combination of cleaning and steaming the interior.

Kashering ensures compliance with kosher laws and restrictions, allowing you to cook and eat kosher foods without worry.

Why Would You Need to Kasher a Microwave?

If you are committed to following kosher dietary rules, you’ll need to kasher cooking appliances and utensils that have been used for non-kosher cooking. This includes your microwave if it’s been used to heat up non-kosher foods.

Here are some examples of why you’d need to kasher a microwave:

  • You kept your old microwave after converting to a kosher lifestyle or joining a kosher household.
  • Your microwave was accidentally used to heat up non-kosher leftovers or takeout.
  • You are uncertain whether your microwave has been used for non-kosher cooking.
  • You share a communal microwave that is used for both kosher and non-kosher foods.

Kashering the microwave removes any absorbed particles, flavors, or residues from non-kosher food so you can feel confident using it for kosher cooking going forward.

How Does Microwave Kashering Work?

Microwave ovens cannot be kashered with heat like metal cookware. Instead, kashering a microwave relies on thorough cleaning and steaming the interior.

Here’s an overview of what’s happening during the process:

  • Cleaning: A deep clean removes any visible food particles or residue from all surfaces.
  • 24 Hour Rest: The microwave is left unused for 24 hours or longer to allow any absorbed particles to dissipate.
  • Steaming: Water is repeatedly boiled inside the microwave, producing steam that penetrates and loosens any remaining absorbed particles from the interior walls and glass turntable.

The combination of cleaning, standing time, and steam effectively purges your microwave of any non-kosher traces.

Step-by-Step Guide to Kasher Your Microwave

Ready to make your microwave kosher? Follow these steps:

Supplies Needed

  • Bowl or large cup for boiling water
  • Sponge or cloth
  • Microwave-safe cleaning solutions
  • Water


  1. Unplug the microwave and let it cool completely before cleaning.
  2. Wash any removable parts – like the glass turntable, racks, or trays – in the sink or dishwasher. Use soap and hot water.
  3. Clean the interior with a microwave-safe all-purpose cleaner using a sponge or soft cloth. Pay special attention to the glass turntable and the interior walls and ceiling where splatters may have accumulated. Avoid using abrasive sponges.
  4. Clean the exterior with an all-purpose cleaner and sponge or soft cloth. Shine up that stainless steel or wipe fingerprints off the control panel.
  5. Clean the door seal with disinfecting wipes or a wet cloth. Make sure no crumbs or splatters linger around the rubber seal.
  6. Let it rest. Leave the (unplugged) microwave unused for 24 hours or longer. This allows time for any non-kosher food particles or residue to dissipate.
  7. Fill a microwave-safe bowl with water. The vessel should be large enough that the water can eventually boil over into a steaming cascade.
  8. Heat the water for 10 minutes, letting it boil and steam the interior. Make sure you’ve removed any turntables or racks first.
  9. Keep heating in 10 minute intervals. Reposition the bowl in a new spot and repeat 2-3 more times, until steam has penetrated all interior surfaces.
  10. Use it for kosher cooking! Your microwave is now ready for you to heat up kosher foods.

And that’s it – your microwave is now kosher! The entire process takes less than an hour of active cleaning time.

Tips for Kashering Your Microwave

Follow these tips for the most effective kashering results:

  • Use the highest heat setting to generate the most steam.
  • Let the hot steam penetrate for 5+ minutes before wiping interior surfaces.
  • Position the steaming bowl in different locations each time to reach all areas.
  • Leave the microwave door closed while steaming for maximum saturation.
  • Ventilate your kitchen during the steaming process to let moisture escape.
  • Wipe down interior surfaces after the final steaming to remove condensation.
  • Run an empty microwave cycle for 5 minutes at the end to eliminate any odors.
  • Use a new microwave-safe bowl reserved only for kosher use if possible.
  • Avoid microwaving non-kosher foods once kashered. Stick to reheating kosher items only.

What Items Can’t Be Kashered?

While the kashering process works wonders for metal cookware and microwaves, some items cannot be made kosher at home. These include:

  • Plastic, acrylic, or melamine dishes and utensils
  • Earthenware like ceramic dishes or clay pots
  • Porcelain sinks, tubs, or dishware
  • Glass cooking surfaces like ranges or bakeware
  • Natural stone like granite countertops

Porous materials like plastic and clay absorb non-kosher particles that cannot be removed by steaming or boiling. Your best bet is to replace these items with new kosher versions.

For large appliances like stovetops, you may need to contact a rabbi to arrange for professional kosher certification.

Related: Can Clay Pots Be Used in the Microwave?

Maintaining a Kosher Microwave

Once your microwave is kosher, maintaining that status requires some care and common sense:

  • Never microwave non-kosher food items. This includes using it to reheat takeout or leftovers that aren’t certified kosher.
  • Keep your kashered microwave separated from any non-kosher ones. If you share a communal microwave, label yours.
  • Use microwave-safe coverings like plastic wrap or lids over food. This prevents splatters which can then absorb into the interior.
  • Clean spills immediately before residue can seep in. Use a wet cloth followed by a dry one.
  • If non-kosher food does make its way inside, kasher again straight away. Don’t wait!
  • Consider keeping a second non-kosher microwave for occasional use to avoid repeated kashering.

Following these microwave kosher practices will allow you to keep your appliance in compliance for all your kosher cooking needs!

Frequently Asked Questions

Still have questions about making your microwave kosher? Here are answers to some common FAQs:

How long does kashering a microwave take?

Active cleaning time is less than an hour. Combine that with 24+ hours of idle time for the best results. Actual hands-on time is only about 10-15 minutes of cleaning plus 30 minutes of steam heating.

Do I need to kasher a brand new microwave?

If the microwave is brand new out of the box, kashering is not required. However, consider running an empty “steam clean” cycle for 5 minutes in case of manufacturing residues.

Can I speed up the process by not waiting 24 hours?

It’s not recommended. The waiting period allows for full dissipation of absorbed particles. Rushing this step may result in an improperly kashered microwave.

How often do I need to re-kasher?

You shouldn’t need to re-kasher often if using the microwave for only kosher foods. If non-kosher food is heated, kasher again immediately. Consider keeping a separate non-kosher microwave to avoid frequent re-kashering.

What about the vent fan and outlet?

Focus kashering efforts on the interior. The vent fan and exterior outlet do not contact food directly. Thoroughly clean these areas and the kashering steam will indirectly address the closest surfaces.

Can I use a damp sponge or just water instead of microwave cleaner?

It’s recommended to use a true microwave-safe cleaning solution for the most thorough results, especially when addressing built-up grease and fat splatters. Kosher observance requires meticulous standards.

In Conclusion

Transitioning to kosher cooking means ensuring your microwave meets kosher requirements if it’s been used for non-kosher cooking. Kashering a microwave through cleaning and steaming allows you to feel confident about its status. Follow the steps carefully and avoid non-kosher use afterwards to keep your microwave in working kosher order for all your cooking needs!

By Rosie Elliott

I’m Rosie. I’m a professional chef with experience in Western, Mediterranean, and Italian cuisine. I’ve been cooking for over 15 years, and I have two daughters that keep me busy!

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