A full melt pool can be defined as the wax being heated to an extent that it reaches the edge of its container – generally it should be up to ¼ inch deep. This depth allows the fragrance to diffuse into the room without being burnt off. It is important to bear in mind that all fragrances have different specific gravity and flash points which effect the burn of your candle and thus the size of the melt pool. Heavy fragrance oils such as White Lotus or Vanilla will have higher flash points and will require larger wicks, whereas the opposite is true for lighter fragrance oils such as Lemon. We would advise you to look at the flash points of the fragrance oils you are using and adjust the wick size accordingly.