Gas Mantle - Production

Production

To produce a mantle, cotton is woven into a net bag. impregnated with soluble nitrates of the chosen metals and then heated; the cotton burns away and the nitrates are converted to nitrites, which fuse together to form a solid mesh. As the heating continues, the nitrites finally decompose into a fragile mesh of solid oxides of very high melting point.

Early mantles were sold in the unheated cotton mesh condition, since the oxide structure was too fragile to transport easily. The mantle was converted to working form when the cotton burnt away on first use. Unused mantles could not be stored for very long since the cotton quickly rotted due to the corrosive nature of the acidic metal nitrates, a problem which was later addressed by soaking the mantle in an ammonia solution to neutralize the excess acid.

Later mantles were made from guncotton (nitrocellulose) or collodion rather than ordinary cotton, since extremely fine threads of this material could be produced, but it had to be converted back to cellulose by immersion in ammonium sulfide before first use, since guncotton is highly flammable and can be explosive. It was later discovered that a cotton mantle could be strengthened sufficiently by dipping it in a solution of collodion, which coated it with a thin layer which would be burnt off when the mantle was first used.

Mantles have a binding thread to tie them to the lamp fitting. Until it was banned due to its carcinogenicity, asbestos thread was used; modern mantles use a wire or a ceramic fiber thread.