Technically this question is a little more complex than it appears. There are general rules such as:-
“do not use ceramics decorated with gold, silver or precious metal in microwave ovens”
Indeed ceramic with any metal should not be used in a microwave oven. However additional rules depend on recognising which type of ceramic is being used. For the consumer this is not an easy task.
All ceramics are not the same!
Ceramics are now made all over the world and it is not always easy to establish their source or quality or type. However ceramics that have been fired to a high temperature and are non porous are generally considered to be acceptable for use in microwave ovens. These ceramics include stoneware, porcelain, bone china, and vitreous cookware. Other ceramics which have not been fired to a high temperature have to be used with caution. For these type of product to be used safely there is a need to ensure that they are both dry and have not absorbed water. This can happen in many circumstances particularly during washing or in storage in the fridge. These products need extensive safety instructions to be used safely.
Top brands help the consumer by labelling their products as ‘microwave safe’. Less well known products cannot give this assurance and often do not label at all. So buyer beware and if in doubt do not use in a microwave. Look out for BS or CE standards as a sign of meeting a quality standard.
In summary, most high fired ceramics are suitable for microwave oven use. Lookout for the labelling used by branded products to give reassurance on acceptability for microwave oven use. If in doubt “keep out” is a good motto to remember!
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More information and other technical articles on pottery and ceramics can be found at my website The Potters Friend
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