480 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS world uses the C.S.M.A. methods•, which provide a valuable means of comparing the flammability hazards of various formulations. Felton and Yeomans • recently suggested an alternative method, using a 12 oz drawn steel aerosol can as a combustion chamber, and a sparking plug as an ignition source. The flammable nature of the solvents used in the conventional hair lacquer renders the use of flammable propellants, such as hydrocarbons and vinyl chloride, inadvisable except in limited amounts in combination with the chlorofluorohydrocarbon propellants 1 1 and 12. In the U.S.A., formu- lations containing propane and propellant 1 1 have been used. The formu- lation given below was tested by C.S.M.A. members 23, and the recommended classification was "nonflammable". XI E. 755 (PVP/VA copolymer) Lanogene .... 'Silicone .... Perfume .... Absolute ethyl alcohol Propellant 11 .. Propane .... 0.750% 0.060% 0.030% 13.995ø./o 77.000% 8.000% If 80% by weight, or more, of a chlorofluorohydrocarbon propellant is used, even with highly flammable solvents, the flammability hazard is negligible due to the flame inhibiting properties of these compounds. This has been confirmed recently during tests carried out by Kempe 2•. The ratio of propellant to concentrate will, however, produce a spray containing a high proportion of fine particles which is undesirable. A product contai- ning 70ø//o byweight of a mixture of propellants 11 and 12, and 300//0 of lacquer concentrate will give a flame projection of 9-10 • when tested by the C.S.M.A. flame projection test, but as the ratio of propellant to concentrate decreases, the flame extension increases until a product containing 65% concentrate and 35% propellant 12 will produce a flame extension of almost 2'. It should be mentioned that the discharge rate, and the spray pattern influence these results. For water-based hair lacquers, containing a film former dissolved in aqueous alcohol and pressurized by a hydrocarbon propellant, the flame extensions will be of the same order as the conventional 70/30 propellant/ concentrate lacquer. Labelling as "non-flammable" was given by C.S.M.A. members •a for the following basic formulation :--

HAIR LACQUER SYSTEMS AND THEIR EVALUATION 481 xII PVP .......... 2.0% Ethanol (absolute) ...... 41.6% Water .......... 34.4% isoButane ........ 22.0% CORROSION When a mixture of propellants 11 and 12 is used for a pressurized hair lacquer, the water content of the finished pack must be kept to a minimum to prevent the occurrence of serious corrosion. It was thought that the cause of the corrosion was due to the acid produced as a result of hydrolysis of propellant 11 until Sanders 25 showed that the major cause for the develop- ment of acidity was due to the reaction of ethyl alcohol with propellant 11. Following this discovery, further work carried out showed that nitromethane added at 0.3% to propellant 11 was an efficient stabiliser for this alcohol/ propellant system 26'". The use of propellant 12 alone, usually at about 35ø,/0, considerably reduces the risk of corrosion, and many pressurized hair lacquers using this system are now being marketed. It should be noted that aluminium containers used for any t•vpe of hair lacquer must be internally lacquered with a system giving 100% protection. When tinplate containers are to be used for water-based hair lacquers, the internal protection of the container becomes of paramount importance. Details of the various lacquer systems used for the body and side seams of tinplate containers are given by Johnsen •8'•9, and Garten aø. Prolonged shelf tests are necessary for water-based hair lacquers, and test containers should be filled on a production basis as well as in the laboratory, because there are some factors not yet fully understood which affect shelf life. The amount of air present in the containers is certainly an important factor. COST The chlorofluorohydrocarbon propellants are expensive by comparison with the hydrocarbon propellants and, usually, unless the concentrate in- cludes expensive perfumes or other ingredients, with the concentrate itself. Propellants 11 and 12 are normally used, as cost rules out the use of pro- pellant 114, despite its advantages in some respects. The tendency to use high concentrate/low propellant ratios has been encouraged by the pre- ponderance of pressure filling equipment available, and further economies result from the increased filling rates.