MAGNESIUM RIBBON OR WIRE Metallic magnesium in the form of ribbon or wire. Lamps are supplied for holding the ribbon, but it is sufficient to cut or break off the length required, hold in pincers or in any other way, and apply a light. The ribbon will give slightly more light, weight for weight, than the pure powder, unless the latter is burned in a form of lamp insuring complete combustion. When using magnesium ribbon for printing by contact, i in. of ribbon may be considered equal to four minutes' exposure to an ordinary flat gas flame at the same distance. The average weight of magnesium ribbon is t gr. per 5 in., or about •5 g. per too cm. Ribbon burned in oxygen gives a remarkably powerful light ; a lamp for burning ribbon in this way was devised by McLellan in i882, and an improved form was placed on the market by the Platino type Co. in 1899. Ribbon tarnishes and, con sequently, deteriorates quickly, and should be kept in an air-tight vessel ; the tarnish can be removed by drawing the ribbon between smooth folded glasspaper. The ribbon gives off a
considerable amount of smoke. Sometimes a pad of damp cotton-wool lint is supported over it, this absorbing most of the products of com bustion.
A method of making ribbon into a net of coarse mesh has been recommended for con venience when burning a large quantity and to produce more even illumination, particularly when enlarging. Two L-shaped pieces of tin plate or copper are cut, and the ends of the strips of ribbon are then fastened on one of the L-shaped pieces by pasting on a strip of paper. When the mesh is complete, the other piece is clamped on top. The lower, free corner of the network may then be lighted, and the whole burns rapidly.