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Use Your Microwave Safely

Do you check the labels and materials of your containers before heating them up? 

In most kitchens, we will find an assortment of different materials used in our containers – glass, plastic, ceramic and metals. But all food-grade materials are not similar. Let’s take a closer look at common materials used in food containers, and if they are microwave safe.


Containers made of glass are often microwave safe, but those who aren’t may have micro-bubbles which may expand to the point where the glass breaks or shatters. Do also make sure that any glassware with a colorful coating, finish or stain should be marked for use with food or a microwave safe indication before attempting to use in food preparation. The dyes, pigments or stains may not be food grade.

If you are unsure of whether your glass is safe to heat or not, try microwaving it while it is empty for one minute. If it is hot to the touch, then it is probably not microwave safe. Any glass container with a metallic trim should never be microwaved, as the electrical currents induced by microwave radiation in the metals can cause sparking and pinpoint heating of the glass.


Food safe ceramics use glazes that are made from harmless materials such as silica, dolomite, kaolin, ball clay, and more. Leaching will occur in these glazes, but it is only a functional and aesthetic issue which has no health impact. However, glazes with metals such as lithium, lead or barium may pose issues to your health.


Due to the nature of plastics, they have a high affinity for fats – plastics that come into contact with an oil-based substance will almost always be irrevocably altered, and the plastic can never become truly clean again. This may cause leaching of the original oil-based substance into the food, even if the plastic was originally food grade.

Plastics that are not microwave safe may leach harmful substances when heated into a microwave oven. Never microwave foods covered with a plastic wrap that is not microwave safe.

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