It is a process similar to casting metal into a mould. Later low-quality clay pipes were made by slip casting in a mould. Air pressure forces the metal into close contact with the mould. The dies are prepared by spraying the mould cavity with lubricant. Sand casting has many defects that can occur due to the mould failing. An opening is machined into the surface of the mould on the parting line. Too moist, and mould and contamination may occur. Some showed problems with moisture and mould. They often produce copious amounts of honeydew which encourages the growth of sooty mould. Part construction begins by applying materials to the lower mould. There was a halo of inhibited bacterial growth around the mould. The original negatives had suffered extensive harm, including shrinkage and mould damage. The process is essentially that of a mould. Seven statues have been cast from the original mould. The intensity of this depends on the type of mould board.