Making Tea in a Microwave: Why not?

I often receive interesting questions through the RateTea contact form; with permission from the asker, I am posting one of these questions here, as I think the question and answer may be relevant:

The question:

Hello,
I generally drink black tea but decided to start drinking green tea too. When I read these instructions for brewing green tea bags, they always refer to pouring hot water over the bag. What is wrong with using a cup in the microwave to the desired temperture and then putting the tea bag directly into it. BTW, I am currently using Kirkland Japanese Tea for starters. Also, the box says to steep only for 30 seconds or so but I read on sites to brew up to 2 minutes or more.

Thanks, if you can help.

Glenn

My Answer:

Hello Glenn!

Thanks for writing!

While a microwave can be used to heat water to brew tea, and the flavor can come out just fine, there are a number of reasons that people tend not to recommend this as a brewing method.

The main reason is that when using a microwave, it can be hard to tell from looking at the cup exactly what temperature the water is. When using a stove, small bubbles start forming and then the water reaches a rolling boil as it approaches the boiling point. In a microwave, these bubbles generally do not form at the same temperatures, and it is even possible to superheat the water (above the boiling point), although this is rare and unstable (the water would quickly start boiling off when you placed a tea bag in it).

Safety is a second reason. Superheated water in a microwave can actually be dangerous, and can cause burns:

http://www.snopes.com/science/microwave.asp

And lastly, it's hard to give instructions. You cannot specify temperature in a microwave, just the power setting and amount of time, and these differ hugely from one microwave to another.

And a new resource:

Also, in response to this question, I added a new page to RateTea, about making tea using a microwave. If you check it out, you will be able to view a brief Mythbusters video of superheated water. You also may be surprised to learn that heating water for tea in a microwave typically uses more energy than even an electric stovetop.