2008 TRI/PRINCETON CONFERENCE 277 Figure 4 shows values of the dry tress reduction of combing force (%) after treatments using oils and butters. In dry condition combing analysis, the reduction of combing force percentage is around 19% and statistically different after treatments with Brazilian nut, passion fruit seed and mineral oil. Once again, butters rendered negative values of reduc- tion of combing force percentage. This results point that the lubricating effect of oils is low pronounced to dry tresses. Figure 3. Average values of wet tresses reduction of combing force percentage (%) after treatment with oils and butters. Figure 4. Average values of dry tresses reduction of combing force percentage (%) after treatment with oils and butters.

JOURNAL OF COSMETIC SCIENCE 278 MECHANICAL PROPERTIES Mechanical analysis were performed in order to verify the effect of raw oils and butters on the tensile properties of human hair. Figure 5 shows the stress at break (MPa) data ob- tained for reference and treated hair fi bers using oils and butters. A slight but statistically (p 0.1) increase in the stress at break was observed for the hair treated using ucuúba butter. The other treatments showed no difference compared to the reference. Figure 6 shows the Young’s Modulus data obtained for reference and for the treated hair fi bers using oils and butters. A decrease in the modulus was observed after treatments with palm stearin and sapucainha butter. The other treatments showed no difference compared to the reference. Figure 5. Stress-at-break (MPa) data for reference and treated hair using oils and butters. Each box plot cor- responds to 50 hair fi ber analysis measurements from each hair treatment and the reference. Figure 6. Young’s Modulus (MPa) data for reference and treated hairs using oils and butters. Each box plot corresponds to 50 hair fi ber analysis measurements from each hair treatment and the reference.