Most hair product manufacturers have a salon with professional hairdressers who compare experimental products created by the formulating chemist to a competitor’s product currently being sold. Both formulas are applied and evaluated on the same person (half head test). But before getting to this stage, the chemist may want to conduct lab tests to see how much progress he or she has made against the competition. What follows are three different lab tests to analyze hair formulas for efficiency.
The first is to check the cleansing efficiency of a shampoo. Wash hair swatches and extract them with petroleum ether and ethanol to remove any inherent lipids present.
1. Prepare 12.5cm long tresses (six for each product to be tested). Weigh them, and then soak in ether for 10 minutes. Rinse with 95% ethanol, then with water. Towel dry, then put in 45°C oven for two hours to dry, and reweigh.
2. Soak the tresses for 10 minutes in synthetic sebum, blot with a paper towel and weigh again.
3. Wash by soaking for 30 seconds in 40°C water. Add 1ml of shampoo and use 20 strokes to work it through the hair. Rinse out for two minutes using 40°C water and place in a 45°C oven overnight to dry. Soak the control and the sebum-treated tresses for 10 minutes in 95% ethanol. Rinse with water and dry overnight as previously. Reweigh all the samples.
The percent lipid removed equals the weight of the lipid removed, divided by the sebum removed multiplied by 100.
The next test is to determine the substantivity of quaternary compounds such as hair conditioners. Prepare six .5 gram swatches per treatment group of blonde or white hair. Set aside one group as the negative control. Another group is soaked three minutes in 0.1% solution of hexadecyltrimethyl ammonium bromide as the positive control. The remaining groups are treated with test products as per product usage instructions. The following procedure can be used with either blonde hair or virgin white wool fabric.
Place the damp swatches into a 0.5% solution of Pyrol Fast Bordeaux 2BL in test tubes warmed to 40-43°C on a hot plate for five minutes. Rinse swatches well with water and visually examine them for the intensity of the red color. The deeper the red color, the more the deposition of the cationic into the hair. Comb and dry swatches, and rank the groups for color pick-up (1: no color to 7: deepest red). Photographs can be made and kept in a notebook for future claims reports.
Determine Moisture Content
The last analytical test is to determine the moisture content of hair by gravimetric means. This procedure could be used to justify the moisturizing claims of a hair cream or lotion.
Two three gram swatches of hair are weighed accurately on an analytical balance. The control sample is treated with water and the other sample is treated as per product directions. They are air dried for a minimum of two days. Samples are weighed again and dried two to six hours at 100°C. Each sample is weighed and the percent difference in weights before and after drying is the moisture content of the hair sample.
0.3155gx100=9.8054% moisture loss
Three or four samples of each variable should be used to obtain more accurate results.
Harvey Fishman has a consulting firm located at 34 Chicasaw Drive, Oakland, NJ 07436, firstname.lastname@example.org, specializing in cosmetic formulations and new product ideas, offering tested finished products. He has more than 30 years of experience and has been director of research at Bonat, Nestlé LeMur and Turner Hall. He welcomes descriptive literature from suppliers and bench chemists and others in the field.