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