Lead to that of primary lead; some refining processes may be skipped depending on the material recycled and its potential contamination. Of the sources of lead for recycling, lead–acid batteries are the most important; lead pipe, sheet, and cable sheathing are also significant. Contrary to popular belief, pencil leads in wooden pencils have never been made from lead. When the pencil originated as a wrapped graphite writing tool, the particular type of graphite used was named "plumbago" (literally, "act for lead" or "lead mockup"). Lead metal has several useful mechanical properties, including high density, low melting point, ductility, and relative inertness.
Lead burning is a soldering process, using plumber's solder (80% lead / 20% tin) and is carried out at low temperature, with a natural-draught propane blowtorch. Today, even wiped joints are rare and where an existing lead pipe must be connected to, a proprietary mechanical joint is more likely to be used. In some rare cases within the chemical industry, lead burning is used for pipework, where acid-resistant tanks and pipes are required to be made of lead rather than steel. Niche uses for lead burning include the manufacture of lead plates for lead-acid batteries and for electro-plating electrodes. Lead burning is