I have been drinking exceptional puerh lately, and I have noticed that on older tea, usually 10 or more years, there is a fine white layer on top of the liquor. It is usually only there for a little bit, and then goes away. If I blow on it lightly, it changes pattern, or heavily then it flies off only to rebuild in a moment.
The patterns are complicated, shifting, and have strange, jerky movement to them (like watching the water-skimming bugs from creeks in Georgia as a kid). I asked my puerh guy, and he said (in Korean) that it is Eun Moo, or "Cloud and Fog." I think this is the Korean name. I have seen it on many mid-to-older teas, but this weekend I had a sheng from the early 70s, and it was the thickest, most beautiful one yet. I took a video, which I will try to get on youtube and post later.
Does anybody know what I am talking about? Have you seen it? Can anyone actually explain what it is? There are some interesting physics in play here, but I just can't wrap my brain around it. Thanks!