FMCD
From Wiki Weed
Full Melt Clear Dome— The top grade of water hash and dry sieve, which is indicated by the way it bubbles when heated. In order to see this most clearly, it’s best to use a screen and smoke the hash on its own. Applying light, indirect heat will cause the hash to start to melt and puddle — if it’s really good, you’ll see large, clear bubbles forming readily as the hash melts away to basically nothing.