As with a conventional oven, over time a Big Green Egg gets gunked up with fat, grease and other undesirable detritus. When the ceramics glisten with black, fatty deposits and there’s an aroma of fat as the Egg warms up, it’s time for a clean.
Not with Mr. Muscle though. I restored the Egg by performing a controlled clean burn. The result was an Egg nearly back to the state it was when purchased.
The Cook's Digest 