Pencil thereby pushing a new tip to the top. Invented by Harold Grossman for Empire Pencil Company in 1967 and subsequently improved upon by Arthur D. Little for Empire from 1969 through the early 1970s; the plastic pencil was commercialised by Empire as the "EPCON" Pencil. These pencils were co-extruded, extruding a plasticised graphite mix within a wood-composite core. Residual graphite from a pencil stick is not poisonous, and graphite is harmless if consumed. Although lead has not been used for writing since antiquity, lead poisoning from pencils was not uncommon. Until the middle of the 20th century the paint used
Lead smelting methods are usually used to remove the remaining non-lead components of the mixture, for example the Betterton-Kroll process and the Betts electrolytic process. The non-lead metals are usually sold to other metal processing plants. The refined lead may be made into alloys or directly cast. People who operate or work in such plants are also referred to as smelters. Galena, the most common mineral of lead, is primarily lead sulfide (PbS). The sulfide is oxidized to a sulfite (PbSO) which thermally decomposes into lead oxide and sulfur dioxide gas. (PbO and SO) The sulfur dioxide (like the carbon dioxide in