The Explosive Reason You Should Never Cook Kale In The Microwave

We all know there are certain materials that don't belong in the microwave. Many of us have likely experienced the consequences of accidentally leaving a fork in our leftovers before reheating them at least once — or twice. Many of us also know that there are many, many types of items (and foods!) that cannot safely be microwaved other than our metal utensils. The reasons range from melting the containers that the foods are in giving, way to chemicals potentially leaking into our food, to the chance of ingesting bacteria from unevenly reheated meat.

However, there are some foods, such as kale, that cannot be microwaved for reasons similar to that of the metal fork — they will spark and, potentially, catch on fire. Because of minerals found in certain foods (in this case, the iron found in kale), some foods have the potential to "arc" (cause sparks to fly inside of a microwave).

A quick look at the U.S. Department of Agriculture's food safety guidelines acknowledges that there are certain foods that have this danger of arcing. Sometimes this is caused by a bad mix of salts and additives (which is typically the case with hot dogs), and sometimes it's because of the minerals of the soil in which they grow (which is the case for carrots). While hot dogs and carrots are the only two foods called out specifically, the reasoning behind them of potential additives or minerals can apply to other foods as well, such as kale.

But containing metallic minerals is only one part of this equation. Shape matters, too. When an item is in the shape of a rod (like a hotdog) or in a shape that has a lot of jagged edges (like the leaves of kale) there's a great chance that there will be a difference in electric properties from one surface area to the next within the electric field of the microwave. The electricity interacts with the air, and this is what causes sparks to fly. The air is key, too, and this is why if certain metallically inclined vegetables are microwaved within a sauce or oil, they will not spark.

In the case of kale, the leafy green has more than one danger factor with regard to the microwave. In addition to its shape and mineral makeup, the salt that is often added to kale can be a contributing factor to arcing. Moreover, if the leaves are particularly dry, they are also more likely to ignite. The bottom line? When it comes to kale, stick to the oven, and add it to the list of things to never put in a microwave.