Water at a preset temperature of about 92 degrees C will flow through the coffee under pressure and the coffee liquor will stream out of the spout. The coffee liquor should run dark at first then as a fine froth known as crema which will cover the surface of the coffee. Ideally the crema will have creamy orange colour. This should take about 20 - 25 seconds - any longer and that bitter taste will be evident in the coffee.

Recirculating Percolators

You will see that there is no reference to recirculating percolators above. This is a deliberate omission. You will recall the comments about the effect of boiling water on coffee. The recirculating percolator process recycles boiling water through the ground coffee for as long as it is allowed to boil thereby extracting the bitter unpleasant taste from the ground coffee. It is possible to make a reasonable cup with a percolator but you will need to stand by the stove and remove the pot from the heat as soon as the coffee is sufficiently infused and without it recycling too many times.