Is It Unsafe to Use Glass Dishes in the Microwave?

Types of Glass

• The microwave is a utilitarian kitchen appliance, not for your fine crystal. If you cherish your crystal or cut glass items, or if you have antiques and collectibles, the microwave oven is not the place to test them. Appreciate these items for aesthetic value and find a utilitarian dish to use in the microwave. If you wouldn't put it in the dishwasher, don't put it in the microwave. Older Pyrex is borosilicate glass and can withstand temperature changes; this glass may be marked heat-resistant or microwave-safe. Some glass is soda lime composition, and there is some question about the safety of soda lime glass in microwave cooking, according to a 2008 Consumer Affairs report. This report indicates that Anchor-Hocking and new Pyrex by World Kitchen both use soda lime glass.

Look on the Glass

• Items with gold or silver rims are often unsafe in a microwave oven, along with items with metal handles or metal parts that are not marked for microwave use. Check the glass for writing on the edge or bottom that identifies whether it is microwave-safe or not. Heat-resistant or microwave-safe kitchen items are usually marked. A symbol showing a rectangular microwave in a circle in a square indicates microwave-safe items.

Test the Glass

• Place the glass item in the microwave along with cold water in a microwave-safe cup. Microwave on high for one minute. If the glass item is cool and the water is hot, it is microwave safe. If the glass container is warm or hot, do not use it in the microwave, the University of Nebraska Lincoln Extension Service warns.

Use Glass in the Microwave

• The University of Rochester suggests that glass is the best container for fatty foods in the microwave. Use glass you have tested or glass that is marked microwave-safe or heat-resistant. Glass and ceramic glass cookware marked microwave-safe and tested for microwave use should be safe, but as with all dangerous items, be cautious. The microwave oven can create arcing and even fire with the wrong products, including staples, twist ties or silverware in a glass dish.