One of the earliest of Auer’s patents (_vide supra_, p. 271) protected the process of collodinisation, which is now extensively employed. The oxide skeleton is dipped into a solution of collodion (the mixed lower nitro-derivatives of cellulose, or cellulose nitrates) in a mixture of alcohol and ether, to which, to prevent shrinkage on drying, a little camphor is added. On account of the inflammability of the mixture, the ethyl alcohol and ether are occasionally replaced by a mixture of methyl alcohol and acetone, but with this less volatile mixture, drying of course is slower. After dipping, the solvents are removed in a current of air, leaving the mantle coated with an exceedingly thin film of collodion, which increases enormously its power of resisting shock and vibration. This film is not removed until the mantle is placed on the consumer’s burner, when on the application of a match it ignites instantly and burns away, leaving the oxide skeleton in the condition to which it was brought in the final stage of hardening and shaping in the factory. The process is now used for almost all kinds of mantles, having been successfully applied in Germany in recent years to those made from artificial silk. The addition of small quantities of various inorganic salts, _e.g._ nitrates of zirconium, magnesium, platinum, thorium, etc., to the collodion solution, has been proposed; these salts make the collodinised product extremely resistant, but have a very harmful effect on the oxide ash when the collodion has been burnt off. The collodinised mantles are cut to length on a trimming machine, and are then ready for packing. * * * * * The present chapter may be concluded with a bare mention of a few disconnected details, selected from the great mass of proposals, suggestions, and developments which have sprung up round the incandescent mantle industry.[520] [520] For a complete account of the mechanical developments, the reader is referred to the monograph ‘Beleuchtung und Lichtmessung,’ by Dr. Börnstein, in Dammer’s _Chemische Technologie der Neuzeit_, Stuttgart, 1910-11, ii. 243-266.