STABILITY OF SOME SPECIFIC EMULSIONS 595 Figure 7. Oil-in-water antiperspirant cream, six months old. Polarized light, 165 X -.... • •-:-'- .• .'. * . : ß. .... . .-. . .. '". V:%.':.r- •.• * ::!•.! ß -: • ½ .:...• *" :'...:.. :.-...'• .'... *' •½:'..,. 'Y'" ..' Figure 8. Oil-in-water antiperspirant cream, filled one day after manufacturing. •hotomicrograph taken 11 days after filling. Polarized light, 165 X ß - •:., • • _ . , .• ß •,". Figure 9. Oil-in-water antiperspirant cream, filled two days after manufacturing. Photomicrograph takcn six months after filling. Polarized light, 165 X -z - '""': i: - ', , .,•.. •.....--......-r Figure 10. Oil-in-water lotion, bulk cmul- sion prior to packaging. Polarized light, 165 X Figure 11. Oil-in-water lotion, five days old. Polarized light, 165 X

596 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 13. Oil-in-water lotion, freshly made. Polarized light, 165) Figure 14. Oil-in-water lotion, one month old. Polarized light, 165 X Figure 15. Oil-in-water emulsion, six months old. Polarized light, 165 X Figure 4 shows the appearance of the freshly made emulsion, the aver- age particle of dispersed phase being about 6/•. When the batch was filled the next day, it gradually set to a firm smooth cream with the microscopic appearance shown in Figs. 5 through 7, which illustrate the change in emulsion character with time. Despite some crystal forma- tion and growth, microscopic changes for such a long period are small. The macroscopic stability is also good. However, when the bulk cream is stored for one day before filling, it is softer the crystals are larger and suspiciously like GMS (Fig. 8). If this bulk cream is held two days be- fore filling it is still softer than the previous one. Figure 9 shows its microscopic appearance after six months. Here, the mechanism is less clear. One possible explanation is that crystallization of material, probably GMS, proceeds slowly and for a fairly long time. The cream takes a rather fragile set which manifests itself over a 72 to 96-hour period. If filled early in this setting period,