The glazed bottom will protect the surface of an object you may wish to set the diffuser on. However, because the oil does not permeate the glaze, this piece is not as effective as an unglazed diffuser. Over time diffusers and aroma lamps may not seem as effective as they are at first. This is normal, and results from a natural tendency of the olfactory sense to adjust to prolonged or repeated exposure to a particular aroma or scent. To overcome this, most people rotate among several of their favorite fragrances at regular intervals.
Oils can stain or damage some materials and finishes.
Do not overfill ceramic diffusers - Because the oil permeates the clay, excess oil will continue to soak through the diffuser until it drips. To prevent spills, remove the light ring from the lamp and refresh as necessary.