What Does "Microwave Safe" mean, exactly?

In the twenty years that I've been making pottery, the three questions that I am most commonly asked. "Are your glazes lead free?" "Are your mugs microwave safe?" and "Can I wash the mugs in the dishwasher?"  To these questions I answer "Yes, absolutely."

I don't use lead in my glazes, and I've taken the extra step to have my mugs certified lead-free by the Brandywine Laboratory in Pennsylvania (here's the link to the report). I figure it's nice to say the glazes are lead-free, but it's critical to have evidence in the form of a lab test to back up the statement. (The report is easily accessible on the home page of Mug Revolution's website.)

I ran across an interesting article this morning while reading the Clay Art digest. The folks over at Good Housekeeping ran some lab tests on commercially produced mugs to see if in fact the mugs were leaching heavy metals such as lead, cadmium, and others. They also ran tests to determine if the mugs were microwave safe. (Here's a link to the article.) They took the tests one step further, and ran them on mugs that were "aged" for one month of average use to see if there was a difference in the heavy metals leaching out of the glazes after regular usage. And, in one case, they found that a new mug was safe, but after being "aged" for one month and re-tested, it did in fact leach lead. They then ask "What does Microwave Safe" mean?

This is how I define "Microwave Safe": One, a mug from Mug Revolution is Microwave Safe if it can withstand repeated heatings in a microwave oven with no damage to the mug over long periods of time. Two, the mug handle does not get excessively warm and burn the user after putting the mug into a microwave for the minimum amount of time required to heat liquid contained in the mug.

In both cases, Mug Revolution mugs pass these tests with ease. I've been reheating coffee and tea in my Mug Revolution mug daily for over five years with no adverse effects. And many people have told me over the years how glad they are that they can take one of my mugs out of the microwave without burning their hand on an overly hot handle.

While there are no actual standards that provide a clear definition of what "Microwave Safe" means, Good Housekeeping calls for refining the meaning of ATSM Standard C1607 to include mugs that have been tested after they have been used for a period of time to ensure that consumers have reliable data reflecting actual day to day use of a mug. They encourage a standard definition of "Microwave Safe" and subsequent requirement of manufacturers to meet the standard on both new and "aged" mugs, and that the product be labeled "Microwave Safe - meets ATSM Standard C1607."

I'm all for this standard. The culture of "buyer beware" that is so prevalent in society today should not extend into having to worry about the mug you are drinking your coffee or tea from causing potential health issues.

I see my coffee has gone cold while I've been writing. I think it's time to publish this  blog entry and reheat my coffee in the microwave!