Your censer (incense burner) needs a proper fill material to give you its best results. Sand, salt, and other materials can be used, but for maximum utility and performance you should use a filler that can hold a shape and, most importantly, trap oxygen beneath the surface.
Have you ever had an incense cone that wouldn't burn to the end? Would you like to be able to burn joss sticks on their sides so there is no leftover little "nub" that doesn't burn? Using the right fill material can help.