A recently mailed-out SD Classic talked about foam appearing on tea. The conclusion was that it was an effect of limonene on styrofoam. I’ve sometimes noticed a similar phenomenon, though, in ceramic mugs: a white foam appears on top of the water, and dissipates slowly with time. The effect seems to be greater when adding a tea bag to hot water than when pouring boiling water over a bag; in addition, it does not seem to depend in any way on the cleanliness of the cup. Friends & relatives have noticed the same thing, and are similarly at a loss for explanation.
I’m assuming you’re speaking of this article : link .
For the record, the article DOESN’T say the foam cup causes the foam on the top of the tea, only that the tea foam reacts with the plastic foam of the cup and “pits” it.
“For the record, the article DOESN’T say the foam cup causes the foam on the top of the tea, only that the tea foam reacts with the plastic foam of the cup and “pits” it.”
True. The original question about the foam was avoided entirely. That’s largely why I’m appealing to the collective knowledge of the SDMB.
One thing in my experience that causes foam on tea is that the water has not been boiling. It may have been heated to near-boiling and kept that way. You can replicate this at home, using hot tap water for one cup and a kettle at a rolling boil for the other. I don’t know the science of why this happens, but I’ve seen it countless times, particularly at restaurants.