Abstract: A method of facilitating the disposal of waste cutting liquid consisting essentially of an emulsion of partly soluble oils and water comprises subjecting a trickling flow of the liquid to the action of a current of hot air at a temperature of from 80.degree. to 250.degree. C. and thus evaporating the water from the liquid. Insoluble oils may be removed from the liquid by decantation before the liquid is subjected to the current of hot air. Preferably the oil which remains after the water has been evaporated from the liquid is used as fuel in the heating of the hot air so that the oil is disposed of. Apparatus for carrying out this method comprises an evaporation tower containing a series of plates alternately inclined in opposite directions to the horizontal and arranged one beneath the other to permit a trickling zig-zag flow of the cutting liquid over the plates from the top plate to the bottom plate in the series.