HAIR LACQUER SYSTEMS AND THEIR EVALUATION 487 or used for formulations which have little stress-raising properties, if further functional tests prove satisfactory. During refrigerated filling operations, the propellant and concentrate delivery nozzles should be kept clear of ice and water. When pressure loading is used, efficient purging or evacuation of the air from the container must be carried out. I must stress that the uncompromising control of every aspect of manu- facture is vitally necessary. Failure of a commercial product harms every- one in the industry, and not only the filler or marketer directly concerned. DISCUSSION }V[R. A. HERZKA: Thesaurosis of the lungs, a!]egedly due to hair lacquers, is now receiving a good deal of attention, and there is one aspect, briefly referred to by you, which I wish to stress. Although publications in the past have dealt mainly with the type of film formers, it could well be that the results of the various investigations now under way will indicate that the particle size of the spray is as, if not more, important than the nature of the film former. Many of the formulations cited in your paper employ propellant concentrations of 70%, and the resulting spray urill be almost equal to that of ar• air fresheneL with extremely small particles which remain suspended in the atmosphere for quite a time, and can thus be inhaled very easily. Such formulations are known to be employed in the United States in order to obtain a spray which is classified as nonflammable. In this country, however, it is doubtful whether there are many packs which employ a propellant concentration in excess of 50%. Consequently I believe that formulations with a low propellant concentration present far less of a hazard, if there is a hazard at all, than the packs utilising many of the formulations which you have listed. THE LECTURER: A considerable proportion of the pressurized hair lacquers marketed in this country do contain prope!lant concentrations in excess of 50%. Considerations of flammability have prompted the use of formulations of this type. The use of lower rates of propellant concentration obviously reduces the proportion of fine particles in the spray cloud and hence the number of fine particles inhaled. Whilst the proportion of fine particles diminishes as the propel!ant concentration falls, there is still a significant proportion of particles of five microns or less. The use of a mechanical break-up actuator, which is necessary for formulations containing low percentages of propellants, results in a diffuse spray cloud of particles possessing lesser forward velocities, and hence the possibility of inhalation of particles tends to increase.

488 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS DR. I-{. I(/3BLER: According to our experience a concentration of more than 20% methylene chloride can cause structural damage to the hair. T}IE LECTURER: I have no direct experience with regard to damage of the hair by methylene chloride, but feel that its use in hair lacquer formula- tions is to be deprecated. Its effect on valve rubbers and polyethylene dip tubing needs careful evaluation, avd it can cause high weight losses on storage. It is prone to hydrolysis, and has deleterious effects on some perfumes. As I mentioned, the falling spray can cause damage to the surfaces of furniture and fixtures. A high local concentration of metlxylene chloride in the air space sur- rounding the user may result. Methylene chloride may have some effect on ciliary activity, which may increase inhalation hazards. DR. H. KOBrER: A good hair lacquer must be removable by washing. Can silicones be completely removed by washing, or do they accumulate in the hair ? T}IE LECTURER: The percentage of silicones used in hair lacquers is relatively low, and I have not heard of any difficulty regarding the removal of hair lacquers containing silicone from the hair. Laboratory tests with hair switches repeatedly sprayed with lacquer containing silicones, and washed between each spraying have given no indication of an accumulation of silicone. DR. H. KOBrER: In the matter of flammable propellants, I wish to state that my experience covers the production of many millions of hair lacquer, utilising vinyl chloride as the propellant. No accident directly attributable to this propel!ant has been reported. T}IE LECTURER: I appreciate the fact that, despite the wide use of flammable solvents and propellants, there lxave been few accidents with conventional hair lacquers. Nevertheless, since the actual concentrates are flammable and the use of flammable propellants aggravates the danger, I believe it is incumbent upon the formulator to develop the least hazardous product possible within limitations imposed by basic considerations of the performance of the product. MR. J. WArnIS: In any system of product /propellant /container, there is a water concentration below which corrosion is iust as severe as if the formula- tion is 'wet'. Thus the use of 75 o.p. alcohol, or specially dried resins, can cause severe corrosion which would not occur if 74 o.p. spirit were used. THE LECTURER: The problem of "dry" formulations does not arise commercially. The alcohol and resins, as supplied, contain water, and it is