core of the winding. Root winding is heated over a greater length and the thickness of the winding will depend on the overlap between turns. Bari-Woollss was probably instrumental in introducing a new factor-redox reduction. In chemistry, this is the opposite of oxidation and can mean the removal of oxygen or, in this case, the addition of hydrogen, which by breaking the bonds of the keratin in the hair, allowed waving to take place more easily. This resulted in addition of a sulfite, bisulfite or metabisulfite to Icall reagents, sulfur dioxide, a reducing agent, being evolved on heating. The only alternative to sulfites at the time would have been mercaptans which are unpleasant to use. However, later alternatives were found which led to the development of cold-waving. Bari-Woollss left Icall in about 1934 to take over the editorship of an encyclopedic volume on women's hairdressing. Developments after 1930 By 1930, the process of permanent-waving was well established and its importance can be gauged if one considers that the majority of middle-class women, at a rough estimate, had their hair set once a week and permed perhaps once every three months as new hair replaced the waved hair. Meanwhile, hairdressers sought to improve the process and reduce the work involved; this meant savings at the lower end of the market and yet more women getting their hair permed. This was also stimulated by pictures of the rich and famous, particularly film stars, who all had their hair permed. This resulted in many copies of the original equipment being made by reputable firms in some cases with innovations of their own: Nestlé. Nessler re-entered the British market under this name, introducing the "Radione" system in which the hair was wound dry and inserted into hollow cellophane tubes sealed at both ends, but contained moistened paper. Also introduced the "oleum" system in which water was replaced by oil. MacDonald. A revolutionary system, as it did not use direct electrical heating. Steam was generated in a separate kettle, or later in small individual kettles, the steam being led by tubes to each "heater". Arrangements had to be made to remove the condensed water, but there was no risk of overheating nor of electric shock, but scalding was a risk. Gallia originated by J. Metelski, is credited with first moistening the hair with a reagent. which gave better results but made winding more difficult. It