208 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Mixtures of plasticisers are also quite common, and are, formulated to get special effects. The crispness of the hair finish is largely a matter of plasticiser content. Using a polyvinylpyrrolidone content of 5 per cent one can use as little as « per cent plasticiser without dusting or flaking and get a relatively crisp finish, but 1 per cent or 2 per cent of plasticiser results in softer and less visible finishes the actual concentration depends to some extent upon the plasticiser used. High plasticiser contents have the advantage of giving increased lustre. The usual solvent is ethyl alcohol, and when packing in aerosol cans this should be substantially anhydrous. For bulk sales and when packing in squeeze bottles many formulators prefer to incorporate a little water as this is said to improve hair manageability, but this is, of course, ruled out when using some plasticiser systems. Iso-propanol also appears to have received some consideration as a solvent, the attraction probably being the absence of duty, the lack of need for denaturants and its ready availability in anhydrous form for aerosol packing. In the past,, I believe that its odour has given rise to some difficulty in perfuming, but it has recently been claimed that this need no longer be regarded as a serious difficulty. Some of the commercial polyvinylpyrrolidone hair lacquers are marketed as combined lacquers/wave sets, but it seems more Usual to formulate wave sets to provide a less permanent, hair finish, their function being, of course, to set the hair into curls after shampooing. Such preparations are now often based on aqueous ethyl alcohol containing'about 2 % of polyvinyl- pyrrolidone together with plasticiser, perfume, etc. Some cosmetic chemists recommend the inclusion of a wetting agent, and indeed this is also done occasionally with hair lacquers intended for use in squeeze bottles which give a rather coarse spray, the idea presumably being to assist the lacquer to spread on the hair. • (ii) Hair Creams Apart from hair lacquers and wave sets primarily intended for use by ladies, considerable interest is being shown, particularly in, America, in the use of polyvinylpyrrolidone in men's hair fixatives. 8 It is generally thought that the market here is larger in tonnage. Such preparation, s can either be similar in formulation to hair lacquers, and such preparations appropriately perfumed are said to be on the American market,, or alternatively they can be made in the form of oily emulsions using polyvinylpyrrolidone in the aqueous phase. ,Such polyvinylpyrrolidone-stabilised creams are fine in texture and• have a,high sur, face gloss in the jar, at the same time imparting a surprising sheen to the.hair without lea,ving it•unduly oily, There appears to be no technical difficulty in the manufacture of such preparations.

POLYVINYLPYRROLIDONE IN COSMETICS 209 (iii) Shampoos The incorporation of polyvinylpyrrolidone into shampoos has been suggested, jø the advantages claimed being improved foam stability and an enhanced lustre on the hair owing to a residual film of po!yvinylpyrrolidone after rinsing. American workers have also claimed that the incorporation of polyvinylpyrrolidone can reduce eye irritation, particularly in shampoos containing antiseptics. (iv) Hair Dyes and Bleaches The final suggested applications of polyvinylpyrrolidone in hair prepara- tions are surprisingly near the established uses in the textile industry. It has been mentioned earlier that polyvinylpyrrolidone forms complexes with many dyestuffs, and it has been shown that when dyeing hair, carrying out this operation in the presence of polyvinylpyrrolidone can result in the polymer being deposited on the hair preferentially, the polymer film then taking up the dyestuff. The Shelanskis 6 have suggested this phenomenon can be used to provide either more permanent tints on the hair or alternatively temporary colourings which can easily be washed out on shampooing. This appears paradoxical, but apparently is bas,ed on different polyvinylpyrroli- done concentrations and different modes of applicatio n . Almost certainly different types of dyestuffs are involved, but no experimental details have been published. An interesting variant of this has recently appeared on the market, both in the U.K. and in the U.S.A., • in the •form of coloured polyvinyl- pyrrolidone hair lacquers. These have the virtue of providing stable tem- porary tints which can be applied to the hair at the same time as the lacquer and can be readily removed with the lacquer by shampooing. Presumably the advantage is that the hair is never actually dyed, and so cannot become damaged. The use of polyvinylpyrrolidone with hydrogen peroxide for hair bleaching has also been suggested in America, where it has been claimed* that the polyvinylpyrrolidone stabilises the hydrogen peroxide solution to give a more effective bleaching agent operating in the absence of either ammonia or ammonium salts. (c) Pre-shave and After-shave Lotions Polyvinylpyr, rolidone is also being used in both pre-shave and after- shave lotions, particularly those for •aerosol a. pp•lica{ion, although this expensive method of ,packing hardly seems essential. 'Typical after-shave lotions are based on about i per cent poly•inylpy,rrolidone in 85 per cent ethyl alcohol, together with perfume., Such products can 0b¾i,ously 'be packed in glass aerosol containers if desired. 12 The polyvinylpyrrolidone is