Pencil sharpener of 6 cuts and takes practice to master without breaking the lead. Specialized sharpeners are available that operate on non-standard sizes of pencil, such as crayons used in primary schools. Sharpeners that have two openings, one for normal pencils and one for larger crayons, are fairly common. An artist's or draftsman's pencil sharpener leaves the graphite untouched and sharpens only the wood (some models can switch from standard to wood-only by an adjustment). The graphite lead is then honed to a sharp point with a lead pointer, which sharpens only the lead without wood. Lead pointers are also used with
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