When it starts to blow steam and make bubbly noises, then it’s done. You can let it on the stove for maybe 1 minute more to get the last sputters of coffee (if you need 3 cups from a 2 cup pot) but never let the water run out.
If you do let the water run out, the small amount of coffee in the bottom part will burn, and it will give a burnt taste to all subsequent brews. You’ll need to thoroughly clean it. I always scrub it clean with a metal sponge(is that the term in english?) and afterwards with sand. Don’t forget to scrub behind the filter and replace the gasket. I also try to scrub out the inside of the small water pipes (very hard to do).
Then I boil it with vinegar. Not very good for the stainless steel, but it does seem to help the taste somewhat.
Even after all this work it will take a long time before the burnt taste is completely gone.
