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

HAIR LACQUER SYSTEMS AND THEIR EVALUATION 480 necessary to exercise stringent quality control of incoming materials, and of manufacturing and filling methods to prevent uptake of additional water. The preparation of virtually "anhydrous" hair lacquer systems is a tedious laboratory procedure. MR. P. MOXEY: What is the incidence of stress cracking in dip tubing? The use of buty! rubber additives in the polythene is not necessary as there are ethylene-butene and ethy]ene-propylene copolymers which are superior. The 24-hour method used by you to determine the possibility of stress cracking is an "accelerated test", which would come as news to the plastics industry, which has not yet been able to evolve such a test. THE LECTURER: The incorporation of additives in the polyethylene used for dip tubing is a comparatively recent innovation in this country. The filler is entirely in the hands of the valve supplier in this matter, and has no choice with respect to additives. The 24-hour procedure described is not an absolute test. The test solution is an active stress-raising agent, and the immersion of the assembled dip tube with the multi-axial stress system created by the interference fit where the dip tube is pushed over the valve housing tailpiece, provides a fairly severe test. Long experience and collation of many thousands of results enable us to determine the suitability of the dip tube for a given product. On occasion the dip tube may be rejected, but in some cases whilst it may not be suitable for products with severe stress-raising properties, it could be perfectly satisfactory for products which have but little stress-raising properties. This is a matter of experience. MR. N. BLACKMORE: In your paper a formulation involving the use of ethyl cellulose to improve water resistance is quoted. In my experience, this resin is so water resistant that it does not wash off the hair even with an alkaline shampoo. This is in contrast to shellac, a widely used water insoluble resin, which is removed with alkaline shampoo. Would you not agree that the extreme water resistance of ethyl cellulose films makes it unsuitable for use in hair lacquers ? TUE LECTURER: Ethyl cellulose has never been widely accepted in this country, principally because of the difficulty of removal from the hair. It has been used to a limited extent in conjunction with the more hygroscopic resins to reduce the undesirable property of tackiness. MR. N. BLACKMORE: Regarding denaturants, could you suggest a system which could be used with National 28-1310. As this resin cannot itself be regarded as a denaturant, two suitable denaturants have to be selected. Out of the list given in your paper one only may be selected from quassin,