Check for a microwave-safe label or symbol on the bottom of any container.
- Glass and silicone are the safest choices for microwave reheating.
- Avoid metal, unlabeled plastic, and damaged containers to prevent hazards.
What Makes a Container Microwave-Safe?
Microwave-safe means the material won't melt, warp, or release harmful chemicals when heated. Manufacturers test containers to meet FDA standards for microwave use. Look for a label or symbol on the bottom, often a microwave icon or the words 'microwave safe.' Containers without this label may not be safe. Even labeled plastic can degrade over time, so inspect for cracks or stains. Glass and ceramic are naturally microwave-safe unless they have metallic paint or trim.
Glass Containers: The Safest Choice
Glass is non-reactive and doesn't leach chemicals into food. It withstands high temperatures without warping. Borosilicate glass handles thermal shock better than soda-lime glass. Tempered glass is also durable and widely used for storage. Check for cracks or chips before microwaving, as damaged glass can shatter. Brands like Pyrex and Anchor Hocking are common, but any plain glass container works.
Plastic Containers: What to Look For
Not all plastic is microwave-safe. Look for the resin identification code, usually a number inside a triangle. Codes 1, 2, 4, and 5 are generally safe, but codes 3, 6, and 7 may contain BPA or other chemicals. Even microwave-safe plastic can stain or absorb odors. Avoid using plastic containers for oily or fatty foods, as they heat unevenly. Replace plastic containers that are warped or scratched.
Silicone Containers: Flexible and Safe
Silicone is heat-resistant up to high temperatures, often around 220°C. It's flexible, making it easy to pop out frozen food. Silicone is non-toxic and doesn't leach chemicals. It's also lightweight and space-saving. However, silicone can be floppy, so use a microwave-safe plate under it. Check that the silicone is 100% food-grade, as some blends may contain fillers.
What to Avoid in the Microwave
Never microwave metal containers or those with metal handles or rims. Avoid plastic containers not labeled microwave-safe, as they may melt or release toxins. Single-use containers like margarine tubs are not meant for reheating. Also, avoid containers with cracks, as bacteria can hide and heat unevenly. When reheating, leave the lid slightly open to vent steam.
How to Test if a Container Is Microwave-Safe
If a container lacks a label, you can test it. Fill a microwave-safe cup with water and place it inside the container. Microwave for one minute. If the container stays cool and the water heats, it's likely safe. If the container gets hot, it's absorbing microwaves and should not be used. This test works for ceramic, glass, and some plastics. Always use caution when removing hot items.