models only had a few tubular heaters, and permanent-waving process took place in more than one stage. As the process became more popular and competitive, a whole head of hair could be processed in one sitting, using up to 22 heaters, some of which might be croquignole. Development of the "reagents" Although heat was required for perming, it was soon realized that if an improvement had to be made over the Marcel method, other means were necessary to avoid overheating and to speed up the waving process. The use of water on its own was an obvious choice, particularly as the hair was already wet from washing, for no other reason than that it prevented overheating, and that steam seemed to improve the process (hence the expression "steaming time"). It was not long before experiments were carried out on the use of additives, and it was soon apparent that alkaline additives improved the results. Thus the profession started using what was called a "reagent", perhaps concocted by the hairdresser himself or sold commercially by the manufacturers of the machine. Two common ingredients were borax and ammonia, which are mildly alkaline (having a high pH) but are relatively harmless. J. Bari-Woollss Until about 1930, most progress was empirical, that is, each hairdresser tended to use a method which he had found to be useful. By then, although some academic work had been done on the subject of hair, Calvete felt that more research should be done on the chemistry of hair, and engaged a chemist by the name of Bari-Woollss, who specialized in the subject. He carried out controlled experiments on known factors such as the effect of heat, water/steam and alkalinity and experimented on variations of the winding process, such as the type of hair, the tension or tightness of winding, the flatness of winding, the overlap and pitch. His practical lectures on the subject proved highly popular among hairdressing professionals, and he wrote a book on the subject. Certain basic factors he pointed out are still relevant today. A point winding is almost two dimensional, rather like the spring of a watch spiral. A root winding is three-dimensional much like a spiral staircase or, more properly, a helix. Thus point winding tends to produce more of a curl, but both produce waved hair when pulled slightly. Point produces a thicker winding and so heat takes longer to penetrate the