The white foam that builds up when I make tea


I microwave water in order to make tea. After it is microwaved and I drop the tea bag(green tea) into the water, thick white foam builds up on the top.

What is it and should I worry about drinking it?

Best Answer

When you boil water in a cup in a microwave, it will often boil without forming bubbles, because unlike a kettle with a rough heating element or inner surface, a clean ceramic cup has few nucleation points. Nucleation points allow pockets of gas to form, which become bubbles as the water boils.

When you add the teabag to the hot water, you are essentially introducing thousands of nucleation points very quickly, and so lots bubbles form very quickly - your foam. You should exercise caution when heating water this way prior to adding a teabag, as if you heat it for too long it can superheat, and will boil explosively out of the mug when you add the teabag.