MEASUREMENT OF STATIC CHARGE ON HAIR 467 Considerable time has been devoted in our own laboratories to the de- velopment of suitable test methods for such experimentation with hair and the following report covers some of the work which we have done along these lines. The production of static charge developed on combing hair after a given treatment was studied in the following ways: (a) By a direct measure of flyawayhess due to static charge, which we have called the "ballooning method." In this method, a tress of hair !.: . . -:,.. . . ..... •½ .•.. -...,.,%.........., - ½.... . ' -- • .•t7.•"•'"% .... .7• • • '" • •" .:: "•i .: • ... "•f...,:. --:• ..... .:: ..: . , . . :'.7• " •T. '"'. ß '%::.z' •.-•': ,' -•:,:.. ß •:.. . :...: - .. ':: ' ' z•12•..: ":"I "*•" '::' ........ *'"" ......... '•.,."'.":. .....,•:,:. ....... ,.,:.. ':,' .. : ,... :. '.: : .'•. .. 7:::"... ß ,,•,.:.. Figure 1.•Apparatus used in "ballooning" method, showing results of •ombining a shampooed tress of hair (let) and the effect of a subsequent •reme rinse treatment which had been shampooed, creme rinsed, or otherwise treated was allowed to acclimate itself in a closed cabinet having a saturated salt solution pres- ent to maintain the desired humidity. The apparatus (Fig. 1) was kept in a room which was air conditioned and during any given series of tests the temperature did not vary more than a few degrees. Swatches were introduced through the arm opening on the side, which was then closed for the acclimation period. After about twenty-four hours exposure to the desired humidity conditions, the tress was then combed by insertion of a

468 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS hard rubber comb through the side opening and a fixed number of strokes given to the hair tress at a definite rate synchronized with the beat of a metronome. For hair tresses which permit build-up of static charge a ZZ.':.-- Figure 2a.--Apparatus used for measurement and photographing of charge, disassembled. Figure 2b.--Apparatus used for measurement and photographing of charge, assembled. ballooning of the hair tress takes place through mutual repulsion of the charged fibers. Figure 1 is a photograph of the apparatus containing two combed tresses. The difference in "ballooning" between the two tresses is