HAIR SPRAY RESINS 597 ..i:.' ..'"% ::.:.•... ß ..•: . '•.•.......,.•,,. .,"":'" .•"•2::... •:i '.,-.•-•.•. -.'•-! .... • : 'a• ...... •"' •:• •:::.• •...' ..•-:-e, .}•.. .a•..:'•, *i•' ..•, ....":: • :'• .•...•. '•,. '•.:'-:-".•-....'$ }.:'t•:.. '•'% ....... . .'::' •-:• :..•'•' 4" •5• • •: •:•" •?:" "..'.:':• :' -'•4, ,'t• :...,. ' .. • ß .. .., ....:•.......,i•.ai.. : :•.' , •. :.::-:•:i .'" ß ...•..." ........ Figure 2. Chamber with Sward Hardness Rocker PVP/VA, Nasuna A/B, shellac, and PVM/MA were tested for mois- ture pick-up at 70 and 90% R.H. Data for 50/50 mixtures of the above resins were also obtained. Unfortunately, this work does not include Resyn 28-1310. EXPERIMENTAL Apparatus The Controlled Relative Humidity instrument (Model VP- 100A*) was modified by replacing the original glass jar with a rectangular Plexiglass chamber (Fig. 1) which has openings for inserting rubber gloves. One additional opening in the top front side was provided for replacing the polished glass plate for Sward Hardness measurements. Because of the large size of the chamber, two additional fans were included for increasing air circulation. In the lower part of the cham- ber is installed a Sauter Balance• with a scale range from 0-1000 rag, * Blue M Co., Blue Island, Ill. • Sauter Co., Ebingen-Wfirtt., Germany.

598 JOURNAL OF THE SOCIETY OF COSMETIC CIIEMI? I'? ß :. .-: ... Figure 3. $auter balance and weighing dislies with 2 mg divisions and 1 mg sensitivity. In order to run hardness measurements simultaneously with moisture pick-up, a Sward Hardness* instrument was inserted into the top part of the chamber (Fig. 2). For cooling, tap water was used, which made it possible to adjust the rela- tive humidity from 50% up to 90%. Lower relative humidities could have been obtained by the use of colder circulating water, but that range was of no interest in these experiments. A constant temperature of 29.5 øC was maintained in the chamber for all tests. It was possible to control the temperature in the chamber within + 0.05 øC and the relative humidity within + 0.5%. The usual manner of obtaining relative humidity utilizes dry and wet bulb thermometers. In general, wet bulb readings depend on the air velocities over the wet wick. At lower air velocities, higher wet bulb temperature will result, and hence a higher humidity reading will be made. By the use of a Bendix Psyehron Model 566t which is de- * Gardner Laboratory, Inc., Bethesda, Md. t The Bendix Corp., Baltimore, Md.