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From the 16th century, all pencils were made with leads of English natural graphite, but modern pencil lead is most commonly a mix of powdered graphite and clay; it was invented by Nicolas-Jacques Conté in 1795. [60] [61] It is chemically unrelated to the metal lead, whose ores had a similar appearance, hence the continuation of the name.
Most pencil cores are made of graphite powder mixed with a clay binder. Graphite pencils (traditionally known as "lead pencils") produce grey or black marks that are easily erased, but otherwise resistant to moisture, most solvents, ultraviolet radiation and natural aging.
In spite of the name, pencil leads do not contain the toxic chemical element lead, but are typically made with graphite and clay, or plastic polymers. The downside of mechanical leads are that they are not as strong as traditional pencils. Wooden pencil lead is bonded to the outer wooden case, therefore providing more lead protection and strength.
A copying pencil, also an indelible pencil or chemical pencil, [1] is a 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. [2] [3]
Primary grade synthetic graphite can approach the good lubricity of quality natural graphite. Natural graphite is derived from mining. The quality of natural graphite varies as a result of the ore quality and its post-mining processing. The end product is graphite with a content of carbon (high grade graphite 96−98% carbon), sulfur, SiO 2 ...
In 1802, the company patented the first pencil lead made from a combination of kaolin and graphite. In 1848, Joseph's sons, Karl and Ludwig, took over the family business, and the production was relocated to the Bohemian city of Budweis (České Budějovice, within the current Czech Republic). The products were given awards in many world ...
Plant-based protein powders—made from rice, peas or soy—were found to contain triple the amount of lead compared to whey protein powders, which are made from the liquid byproduct of cheese ...
Lead (/ l ɛ d /) is a chemical element; it has symbol Pb (from Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to ...