360 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS methane. For these tests, "Empicol L.Z.V." paste (supplied by Marchon Products Ltd.), "T. J." paste (supplied by Chas. Bedeman, Ltd.) and "Cycloryl pastes 30C50E and 33" (supplied by Cyclo Chemicals, Ltd.) were used. On the other hand, corrosion has always been experienced with formulations based on triethanolamine lauryl sulphate, and in this respect our findings appear to be completely opposite to those reported from the United States. SHAVING CREAMS According to van Beem '5 the following are satisfactory aerosol shaving creams for use in lacquered containers: Stearic acid 20.6 g. Triethanolamine 9.4 g. Lanolin 1.5 g. Glycerin 5.0 g. "Texapon extract N.40"* 9.5 g. "Comperlan"* 0.6 g. Water 200.0 g. II Stearic acid 20.6 g. Triethanolamine 9.4 g. Lanolin 1.5 g. Glycerin 5.0 g. "Tween 60"• 15.0 g. Water 200.0 g. * Supplied by Deutsche Hydrierwerke, GMBH, Dusseldorf. ½ Supplied by Honeywill-Atlas, Ltd. The charge in each case amounts to 90 parts by weight shaving cream and 10 parts by weight dichlorodifluoromethane. An interesting point arose with Formulation II. It was found that slight corrosion took place when the amount of "Tween 60" was increased to 25 g., and very severe corrosion, in spite of the internal lacquering, took place when this was increased further to 50 g. This is another example of the care necessary when formulating aerosol products. (See Fig. 5.) SUN TAN OR SUN DEFLECTANT PREPARATIONS Sun tan, also known as sun deflectant, preparations are very popular, and a number of sun-screening agents are satisfactory for use in this type of aerosol pack, viz.:

TECHNICAL ASPECTS OF AEROSOL PACKAGING 361 Menthyl salicylate Methyl-para-dimethyl amino benzoate Homo-menthyl salicylate 2-Hydroxy-4-methoxy benzophenone Homo-menthyl salicylate has been suggested because its cooling effect on the skin is less than that of menthyl salicylate. •6 The following materials have been found to be satisfactory as vehicles for the above sun-screening agents: Paraffin oil Iso-propyl myristate "Cetiol V" (supplied by Deutsche Hydrierwerke, GMBH, Dusseldorf) Alcohol These vehicles may be used singly or blended to suit individual require- ments. The incorporation of silicones as water repellents, particularly in alcoholic sun tan lotions, has been suggested, '-7,•8 and silicone fluid MS.555 (supplied by Midland Silicones Ltd.) has been found to be compatible with the common propellents. Five to ten per cent sun-screening agent is dissolved in the vehicle(s) and 40-50 parts by weight of the lotion itself is packed with 60-50 parts by weight of propellent mixture. The propellent mixture itself normally consists of either a 50: 50 mixture of dichlorodifluoromethane and trichloro- monofluoromethane or a 40:60 mixture of the former with dichlorotetra- fluoroethane. HAIR LACQUERS The literature mentions three basic materials for use in aerosol hair lacquers, viz., ethyl cellulose, shellac and polyvinyl pyrrolidone. Experiments carried out with the ethyl cellulose formulations suggested by Philips'-g have not come up to expectations. The formulations themselves are indeed suitable for aerosol containers, but the resultant film is inclined to make the hair dull and lifeless. Shellac hair lacquers are suitable for aerosol packing providing unbleached' shellac is used and due attention is paid to the moisture content of the formulation and the type of alcohol used. Reference to these two points has been made earlier in this paper. Very interesting indeed is Witjens' formulation, which has been referred to already. 7 Shellac (unbleached, but dewaxed) 5.0 g. Castor oil, B.P. 2.3 g. Propylene glycol 2.3 g. Carbowax 1-6 g.