Update: Of the three juices that I steeped in the thermos, two came out very nicely, and one still needs some work. However the trouble with that one may lie with the juice, not with the thermos. It's a TFA RY4 double which has always given off a chemical flavor to my taste buds- regardless of how long a steep. I compared this recent batch with one that was naturally steeped for nearly 5 weeks, and they both taste exactly the same. Therefore it seems the thermos has done its job cutting the steeping period to a few hours instead of a few weeks. Altogether I am very happy with the results.