Two things to know about melting snow:
Make sure your pot has some liquid water in it to start with. Just adding snow & turning up the heat will make your lovely titanium billy look like a Formula 1 car's exhaust pipe. Do use the lid.
Melting snow takes a lot of fuel. If the ice on the lake is not too thick, use your ice axe to access liquid water. You do have an ice axe with you of course...
