188 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS struction embodying the basic prin- ciples of Worth and Korf-Zentler as .can be seen from C1. 1: As a com- plete unit of manufacture and ap- plication, a container, and exothermic substance therein, at least a portion of said container in contact with said substance being of iraperforate material which readily transmits a liquid therethrough and anotherpor- tion of said container in contact with said substanc• being of material which is highly resistant to the pas- sage of moisture therethrough. The second group of improve- ments are directed at pad con- struction to effect certain types of chemical reactions. Most basic of this group is the U.S. Patent No. 2,431,220 to Evans and McDonough. The broad con- cept of this patent is shown by the fact that before issuing it became involved in no less than seven inter- ferences and although filed it has just issued. That this pad covers the "oil- fired" pad idea as well as the oxida- tion of sheet metal is shown by the following claim. Claim 5 states: A heating pad for the permanent waving of hair having ingredients, certain of which are unmixed but which when in sufficiently intimate contact with each other react to generate heat, certain of said in- gredients when treated with a solvent passing into sufficiently intimate contact with the remainder of said ingredients to generate heat. U.S. Patent No. 2,239,410 to Bonat covered one specific composi- tion of the so-called oil-fired pad. All the claims are directed toward a composition containing glycerine, whose oily feel in the absorbent gave rise to the term "oil" pads. Similarly U.S. Patent 2,350,926 to Reed covers, as is shown in the following claim, the use of hexahy- dric alcohols such as sorbitol, rhanni- tol, and dulcitol. A typical claim, 3, reads: A chemical composition capable of generating heat upon the addition of water thereto, said com- position including a hexahydric alcohol and an oxidizing agent comprising a permanganate which is sufficiently soluble in water to effect the heat-generating reaction upon addition of water to the com- position. Various patents (2,132,681 to Davis, 2,133,115 to Reynolds, 2,144, 811 to Reynolds, 2,153,671 to Mar- kel and Reynolds, 2,153,676 to Reynolds, 2,153,677 to Reynolds, Reissue 21,276 to original 2,153,678 to Reynolds) have been issued on the use of oxidizing of a sheet or sheets of aluminum foil. As stated above, the more important of these were losers in interference• with the Evans and McDonough U. S. 'Patent No. 2,431,220. A third group of patents directed toward the machineless permanent waving art relates to improvements in the clip used to hold the pad in place when the croquignole type of winding was used. It was quite obvious that a paper type clip could be used to hold the Winkel pad about the croquignole wound hair, but Evans and Winkel (U.S. Patent No. 1,925,527) de-

DEVELOPMENT OF MACHINELESS PERMANENT WAVING 189 velope. d the first adoption of the conventional Bishinger croquignole clip to a self-pad holding clip. Evans U.S. Patent No. 1,927,544 was an even greater improvement which was followed by Koehler's U.S. 2,261,163. All of the above are merely the high spots in the development of the machineless art, but hand in hand with this development went the commercial acceptance of machine- less permanent waving. Before January, 1932, may be considered the zero figure commercially for machineless waving although a few pads were sold. From this zero start and battling the already firmly and highly developed elec- trical waving, the machineless pads had reached at the start of the war an estimated sale of four to five hundred million pads per year and represented about 50 to 60 per cent of the total waves given in the permanent waving industry. Even today as the intensity of scientific investigation leads away from thermochemistry to advanced organic chemistry, machineless waving is still holding its total gross volume of pads sold annually, here and abroad.