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,

490 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS sucrose octa-acetate or Bitrex, but what about the second ? Diethyl phthalate tends to make the resin film over-plasticise and greasy, while Cetrimide causes corrosion. Other denaturants suffer also from serious drawbacks of one kind or another. THE LECTURER: Customs & Excise Regulations require denaturants to render the spirit nonpotable. The denaturants must also be difficult to remove. Whilst general principles are laid down, the Customs & Excise will consider sympathetically any suggestions for alternative denaturant systems, if it can be clearly shown that the normal ones recommended are unsuitable. I agree that the use of diethyl phthalate and Cetrimide are open to objection for this type of product. A fair case could be made out for using alternatives, and two denaturants from the class mentioned might well be accepted. These matters are negotiable. MR. R. E. E½•rTo•: It has been stated recently that 60% of hair lacquers which do not contain 0.3% nitromethane develop objectionable odours within two months. Could you please comment on this from your experience ? TH• L•½TURER: In my own experience this is not so. A vast number of hair lacquers containing propellant 11 have been on the market for many years, and I have never encountered a complaint that the perfume had developed an objectionable odour. We recently examined some hair lacquers packed in 1956 and subsequently stored at ambient temperature. These were still satisfactory in all respects, including the perfumes.