DEVELOPMENT OF MACHINELESS PERMANENT WAVING 187 wetting, a capacity for absorbing a uniform weight of water per area and giving up a uniform amount to the exothermic chemical. Investigation of this problem re- sulted in the study of many mate- rials, none of which solved the prob- lem. In the study of papers as an absorbent, Evans and McDonough finally developed a special element primarily composed of multiple layers of crepe paper. This absorb- ent had the water absorptive, wet strength, and water-releasing char- acteristics desired. This invention was the subject of U.S. Patent No. 2,151,692. While the reaction within a machineless pad proceeds automat- ically, nevertheless, we felt that if the operator had visual evidence that the pad was functioning prop- erly, it would not only be an assur- ance and an aid to the operator in checking that she has performed her task properly, but it would also serve to show when the wave was finished. To accomplish this it became necessary to create a pad which contained this signaling unit. By using a combination of mercuric iodide and cuprous iodide, we were ' able to arrive at a pigment which exactly changed colors at hair wav- ing temperatures and reverted to its original color to show as it cooled down that the pad could be removed without affecting the curl. This invention is described in Evans and McDonough U. S. Patent No. 2,196,201. Other improvement modifications of the original Winkel patent which deserve mentioning here are the following inventions. As a means of briefly indicating the scope of the invention one or more claims will be given. The patents are divided into related types of improvements. The first of the following group are directed toward a pad construction which has become increasingly pop- ular since the war, the pad con- struction being adopted by the so- called "oil-fired" m•chineless wav- ing discussed in the second group of patents below and also by the built- in absorbent of the unitary pad- so-called "water-dipped" pads. U.S. Patent No. 2,051,667 to ¾. Worth is the most basic of this group of pads as can be seen from the following two claims: C1.1--a hair waving pad comprising an outer layer of non-absorbent material and an inner layer of absorbent material containing an exothermic material CI. 13--a hair waving pad including a flexible pervious envelope and a backing of flexible material. U.S. Patent No. 2,349,285 to F. Korf and W. Zentler is next most basic as can be seen from C1.28: A hair waving pad comprising a layer of impervious non-soluble material, a layer of porous, absorbent mate- rial, chemical means disposed be- tween said porous and non-porous materials, and means for holding said layers together and confining the chemical means therebetween, thus forming a unitary pad which requires only the application of a liquid to be ready for use. U.S. Patent No. 2,110,667 to F. Racen is a specific type of con-

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-