Microwaves and Tableware

Most kitchen ceramics are designated "microwave safe" but, increasingly, users of ceramics in microwaves can experience the item heating up. The following is some basic information about microwaves and ceramics that will hopefully shed some light on the issue.

Microwave safe - Microwave safe means it’s safe to use the product in a microwave without hurting the oven or having the product immediately harmed in some way. It does not mean the item will not heat up although it’s rare that the product will get so hot that it’s difficult to handle.

Why do some items get very hot when micro waved? Probably because of moisture trapped in the body of the ceramic and the moisture is being heated by the microwave process. This would explain why some pieces seem to not react to microwaving while others get very hot. In very rare instances, after extended time in a microwave (multiple minutes), certain ceramic items can actually give off a vapor or steam and become very hot. These items are no longer microwave safe.

Does microwaving hurt ceramics? If you have a ceramic item that noticeably heats up in a microwave, the life of the product is probably being shortened by microwave use. The item has some moisture in the body and the moisture is reacting to the microwave process. This is essentially a heating/cooling cycle (think expansion/contraction) and will eventually lead to "crazing" of the glaze. Crazing is when many fine lines appear in the glaze.

What grade of ceramic will not react to microwave use? Both porcelain and bone china should be 100% impervious to water absorption and not heat up in microwaves. WARNING - if any ceramic item is decorated with a metallic band or decal IT IS NOT MICROWAVE SAFE. Many formal china and porcelain patterns use this decorating technique.