This isn’t really along the lines the question implied but a microwave shouldn’t be used to heat water for making tea. It’s universally accepted in tea circles that makes horrible tea, but it’s not as clear to everyone why. My take is that the water is heated so gradually that it doesn’t allow a contact surface for dissolved air to transition to a gas state and leave the water, so you end up with more dissolved air than is stable at that temperature (supersaturation of air in water), and frothy tea.
Sources and details are always nice too, aren’t they? This reference theme tea blog rejects a media claim that microwaving tea is better, for health reasons, but they don’t go into that interesting part about why frothiness occurs:
Microwaving Your Tea, The Controversy Explained and Refuted
That theory about frothiness being due to dissolved air I have turned up background sources on before (I’m an engineer but not the most closely related kind, I’m an industrial engineer), and I’ll try to do that again here. Snopes has an article claiming you can, under the right circumstances, actually super-heat water, but I don’t think that’s a standard problem, it’s just interesting:
FACT CHECK: Superheated Microwaved Water
Here is a reference that gets into it, but it’s a discussion, and some of the comments about superheating seem completely wrong to me:
Why when I put a teabag into microwaved water does the water fizz?
Still not satisfying, to me, but this reference on solubility of gasses at different temperatures does work for me (an “Engineering Toolbox” site reference, so if it’s formulas, tables, and graphs that you’re after this is the right place):
That’s really for oxygen, not air, but air is mostly nitrogen, then oxygen, and on from there, so if you checked solubility of those two (and maybe also carbon dioxide) you’d be getting the whole story. Wikipedia explains: air is a mixture of about 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide, and very small amounts of other gases.[1] There is an average of about 1% water vapour.
Lots less air can be dissolved or stay dissolved as temperatures go up. It’s my understanding that the part that’s still missing in that reference is that it’s not just about gradual heating, that the contact surface of a pan heated to much higher than water boiling point provides a driver for this deaeration, which is why you see bubbles of air evaporating out on that surface before actual water vapor transitions phases (although again that’s my take, and I’m bored with looking up these references).
That top part of that graphic is something else altogether, about how much air can be dissolved at different pressures, with water able to hold about twice as much dissolved air at two times typical atmospheric air pressure. I’m not sure when that would come in handy to know. I lived at well above sea level before (at around 8000 feet in the Colorado mountains), and air would hold slightly less dissolved air there (and there was less air to breathe too; much lower pressure), so I guess your tea would be slightly less frothy if you microwaved the water there, but it would still be a bad idea.