Copying pencil the wound. Such risks are not associated with ordinary graphite pencils. While these symptoms may appear after a couple of days they often develop only after weeks have passed since the injury was sustained. Surgery is required to remove the dye and the infected tissue and "the necrotizing action may be so severe and extensive amputation is necessary". Copying pencil A copying pencil, also indelible pencil or chemical pencil, is pencil whose lead contains a dye. The lead is fabricated by adding a dry water-soluble permanent dye to powdered graphite—used in standard graphite pencils—before binding the mixture with clay. Copying
Lead glass Lead glass Lead glass, commonly called crystal, is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40% (by weight) lead(II) oxide (PbO), while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. Lead glass is desirable owing to its decorative properties. Originally discovered by Englishman George Ravenscroft in 1674, the technique of adding lead oxide (in quantities of between 10 and 30%) improved the appearance of the glass and made it easier to melt using sea-coal