Second, they dumped ladles of the stuff into clay pots each of which contained a small amount of clove oil. The water fell through the oil and found the bottom of the pot, shedding some of its burden of phosphorus along the way. These pots were then subjected to a similar process of gentle heating, so that the water trapped beneath the oil was driven out as steam. When these pots stopped blurping and steaming, it meant that all the water was gone, and nothing was left but phosphorus suspended in oil. The oil coated the tiny particules of phosphorus and prevented air from touching them, which rendered the stuff safe.