This morning, as with every morning, I had my coffee. However, today it was burnt, because I slightly overfilled the water. I use an Italian Percolator on a gas top.
Normally, you put it on to boil, and once you hear the water bubbling, the coffee is ready, and chamber C will be full of coffee. As you can see, you fill chamber A with water, loosely fill B with coffee, and the water then rises through B, up through the red pipe, and flows over into C. However, as the picture shows, there is a small valve on A. If you fill the water above this valve, you get horrible coffee. When you hear it bubbling, very little coffee has risen into chamber C, and you have to wait a long time for it to do this, while water also escapes from between chambers B and C (which screw together).
Why does this happen? I cannot think of why there should be a valve to release what is presumably steam. Surely the machine should work regardless? Why does the steam have to be released for the mechanism to work properly - is it linked to the pressure of the system?