Lead burning

Most lead sheet work is formed and sealed by bossing, a mechanical fold or crimp.

This gives a melting point lower than the base metal, allowing a soldering process rather than welding.

A filler rod may be needed for some welds, if there is no convenient way to form sufficient close overlap at a sheet edge.

Excessive use of a filler, rather than an initial close fit, is considered a sign of poor technique.

A variety of fuel gases may be used, but to achieve the high temperature needed, an oxygen supply is always used.

It was first developed along with the early growth of the bulk chemical industry, as acid manufacture required leakproof lead vessels and flow process plumbing to be made.

By using a mouth-blown blowpipe, a gas flame could reach temperatures adequate for lead burning.

As lead burning is a high temperature process, it creates a significant hazard from such dross.

Safety precautions are relatively simple: goggles to protect the eyes from molten metal splash, overalls or dustcoat kept in the lead workshop to stop contamination spreading, and dedicated workbenches equipped with air extraction.

Industrially this is done by weekly checks for blue lines around the gums, a simple indicator for heavy metal poisoning, and by regular urine testing.