I prime them with 3/4 drops on the side and about 12 drops down the center. Fill them and do lots of dry pulls, let them sit for hours. Every time I refil the ceramic is black. I don't think it's the juice, because I have 4 tanks with 4 different flavors and all do it. I also have 4 halo reactors with the same flavors and they take quite awhile to discolor. I've taken to doing dry burns before each refill until the ceramic turns gray but this is a pain. I do very gradually build them up to my desired wattage, 25 watts. Does anyone have any tips? Note: after dry burn I put 5 drops down the center.