Depending on a variety of factors, the water which
reaches the ground beans in a percolator can easily have
a temperature above the optimal brewing temperature,
which can result in over-extraction, and ruined coffee.
What if we made a percolator which had an upper cold
water reservoir, along
with a thermostatic tempering
valve, to mix that cold water into the hot, so that the
temperature is precisely what the user desired.
The valve's output temperature could be selectable, by
the user, from anywhere in the range of 92 - 96C (about
176 - 205C).