486 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS subject of more commercial failures than any other pressurized product, which have been due to a variety of causes, including corrosion of the container, deterioration of the product, incompatibility of the product with the propel!ant, valve failure through blockage, gasket hardening, and the failing off of the dip tube. I would therefore like to stress the necessity for exercising rigid quality control of incoming raw materials, components, and of manufacturing and filling operations. The alcohol and film formers must be handled with extreme care to prevent the uptake of water. Most of them, as supplied, contain a small and unavoidable amount of water. These amounts are not serious, but careless storage, processing, and filling can increase them to dangerous levels. The water content of the finished pack is critical, and may contribute to product deterioration and container failure. Compatibility tests should be carried out on every incoming batch of raw materials, in addition to routine analyses for water content, etc. This is particularly important with shellac. Where cold filling operations are carried out, the minimum temperature to which the concentrate can be chilled without throw-out of the resins and other ingredients, should be carefully established, and plant control should be such that the concentrate is not chilled below this level. If aluminium containers are used, then the integrity and efficiency of the lacquer system should be investigated most carefully. Routine tests, such as checks on the seams of tinplate containers, neck dimensions, and container strengths, must also be carried out. Apart from general valve quality control, particular attention should be paid to the effect of the formulation on the rubber valve gasket. Since the hair lacquer formulations are active stress-raising agents, the possibility of environmental stress-cracking of the polyethylene dip tube used on each batch of valves must be checked. The interference fit constituted by the pushing of the end of the dip tube over the tailpiece of the valve housing in some valves creates a multi-axial stress system which may, especially if active stress-raising ingredients are present in the pack, result in longitudinal splitting of the polyethylene in this region, causing the dip tube to fall off the housing, and the pack to be useless. This has actually happened. A suitable test method is to immerse the assembled dip tube and valve housing in a 2.5% solution of nonyl phenol ethylene oxide condensate (Lissapol NX), for 24 hours at room temperature. If no splitting occurs in the region of mating of the dip tube and valve housing tailpiece, the valves should be satisfactory for most conventional hair lacquer formulations. If, however, splitting does occur, then the valves must be rejected, re-tubed,

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.