/ck/ - Food & Cooking

I've recently started to use a moka pot. Do you think it is better to pour cold or preheated water in it? On one hand with preheated water the coffee should get less indirect heat because it spends less time on the stove top, but with cold water the air in the tank can expand before the water is boiling, so it will push somewhat colder water in the pipe thing first.
Also get that i'm supposed to take it off the heat about the time when the water level reaches the bottom of the pipe (point A in pic related) and the coffee coming out from the top starts to bubble a bit because of the air going through the pipe. What i don't quite understand is why will relatively clear water come out from the top if i keep it on the heat? Isn't it supposed to still pass through the filter? Does the hot air going through the pipe dig a hole in the coffee or something?