Tea Spit

pH paper?

Tea is generally about pH 6 to 6.5 i.e mildly acid side of neutral. I don't believe acidity has any affect on foam or vice versa. I generally suspect washing up detergent when I see foam on catering tea. However, tea seed contains high level of saponin (a natural surfactant - 10 to 15% by weight and an important industrial source). Tea leaf has trace levels of saponin (not much - it's toxic), which may on occasion be sufficient to cause a surface froth. I am not aware what field conditions encourage saponin in tea leaf - a nice study for someone.

Nigel at Teacraft

I hope saponin isn't tremendously toxic?

I've noticed a foamy or scummy froth often when brewing young, raw Pu'er. I rarely see it with other teas.

Disclaimer: No detergent comes in contact with my teaware, just sodium bicarbonate.

/Lew

i only observed lots of "foam"/"froth" with some yunnan golds which have lots of little tiny "hairs" /dust that will (i suppose) allow little bubbles to form and persist when water is poured

Sure, the "hairs" occur a lot in early spring green tea as well. But they aren't what I was talking about, and I suspect they aren't what Jim referred to, either.

/Lew