On Sun, 07 Nov 2004 16:00:48 +0000, Dog Ma 1 wrote:

J Boehm wrote:
I think that you also need to look at the quality of the tea: Some of my
teas become cloudy (opaque) after a while and those do not keep long at
an elevated temperature. Cloudiness is always connected to fine dust in
the liquor

Always? I've read that various tea components (e.g. tannins and caffeine)
react over a few minutes to form sparingly soluble complexes that
precipitate out as a fine floc. My own results with dust-free teas are
consistent with this. In addition, the temperature-solubility profile of
some other components is so steep that a few degrees' drop, especially in
stronger brews, brings on cloudiness.

-DM

I am not a chemist but only a simple physicist and hence try to reduce
phenomena to their simplest cause. I use a Pyrex glass beaker (from a
laboratory) to drink tea and can therefore see the opacity quite clearly.
On a number of Assams I see cloudiness quickly, hence they are not used in
a thermos anymore. However, a few Oolongs and a Turkish tea (low in
tannin) hold up very well and even after 6 hours I cannot see cloudiness.
The taste holds up pretty well too, especially with the Oolongs. I brew my
teas well below boiling, at about 80-90 centigrade, Assams are doused with
boiling water. Maybe it is time for a chemist to speak now ;-)

JB