EFFECTS OF WATER ON HEAT-STYLING DAMAGE 17 EXPERIMENTAL MATERIALS Fine-density, light-brown, virgin hair (20 cm in length) was purchased from Interna- tional Hair Importers & Products Inc. (Glendale, New York). Ethanol (96%), laboratory reagent grade, was bought from Fisher Scientifi c UK Ltd (Loughborough, Leicestershire, UK). Vinylpyrrolidone/vinyl acetate co-polymer (50%) in ethanol (VP/VA E-735®) and quaternium-70 (50%) in propylene glycol (Ceraphyl-70®) were supplied by International Speciality Products (Wayne, NJ). Bis-PEG/PPG-20/20 dimethicone (Abil B 8832®) was supplied by Evonik Industries (Essen, Germany). Methylchloroisothiazolinone and methylisothiazolinone 1.5% (Kathon CG®) were supplied by Rohm and Haas (Morges, Switzerland). METHODS Preparation of heat-protection spray formulations. Table I describes the prototype formula- tions tested in this study. The “wet” spray was adjusted to pH 6 with sodium hydroxide solution. Hair preparation. Hair was cut into 1.5-cm-wide tresses (approximately 1–2 g in weight, including the bindings). Each tress was clipped at the edge, 41 mm from the bindings, to mark the start of the area to be treated with straightening irons. The hair tresses were dried for two days in a glass dessicator over calcium chloride at room temperature. Blow- drying was always avoided, as this may have caused heat-styling damage and introduced extra variability into our experiments. Treatment with straightening irons—a comparison of wet versus dry hair. In experiments com- paring heat damage in wet and dry hair, tresses were wetted by immersion in tap water for 15 minutes ahead of the heat treatment. Surface water was removed with tissue paper before applying the straightening irons. For tests on dry hair, the tresses were heat treated immediately after removal from the dessicator. Table I Prototype Heat-Protection Spray Formulations Material % w/w “Dry” spray “Wet” spray Vinylpyrrolidone/vinyl acetate co-polymer (50%) in ethanol 8.00 8.00 Quanternium-70 (50%) in propylene glycol 2.40 2.40 Bis-PEG/PPG-20/20 dimethicone 1.00 1.00 Fragrance 1.00 1.00 Methylchloroisothiazolinone and methylisothiazolinone (1.5%) in water — 0.07 Water — 87.53 96% Ethanol 87.60 —

JOURNAL OF COSMETIC SCIENCE 18 The tresses were heat treated with ghd IV® straightening irons with 2-cm-wide ceramic plates at 175°–185°C (ghd UK, Silsden, West Yorkshire, UK). The tresses were wrapped in Post-It® paper at their root end, the lower edge of the Post-It® paper marking the top of the area to be heat treated. The tresses were treated with straightening irons for fi ve seconds. The irons were held in the same place throughout the treatment. Wet hair was put back into tap water for three minutes before being treated again. Each time, surface water was removed with tissue paper before applying the straightening irons. Dry hair was simply allowed to cool for three minutes before the start of another treatment. Treatments were repeated three times in each session, after which all the hair was put back into the dessicator for two days. In total, each tress was subjected to 4 × 3 treatments, which equates to a total treatment time of 60 seconds. Repeated fi ve-second heat treatments were selected for this study, as (a) they were realistic and (b) they made our measurements more sensitive to the effects of water, which evapo- rates very quickly. In reality, consumers and hair stylists quickly run straightening irons down each section of hair two to three times. Irons are, therefore, never in contact with any one part of the hair for more than a few seconds. A fi ve-second treatment time (with- out moving the irons down the switch) was selected to represent the heat exposure during one complete styling session. Long, extended treatment times, of, say, 5–30 minutes, as used by McMullen & Jachowicz (5), were not appropriate for our study. Longer heat treatment times are, perhaps, most suit- able for studying protein damage or testing the effectiveness of insulating materials. They are not suitable for investigating the effects of water, since the water evaporates within seconds. Treatment with straightening irons—single-dose experiments with “wet” and “dry” products. In single-dose experiments, 0.1 ml of product was applied to each tress before heat treat- ment. The tresses were wrapped with Post-It® paper, as described above, to clearly mark the area for heat treatment. The product was applied, from a syringe, to the top end of the exposed part of each tress (0.05 ml on each side) and spread downwards, just once, with the fi ngertips. The tresses were left to dry for two minutes before applying the straightening irons. The hair was treated with straightening irons for fi ve seconds. The irons were held in the same place throughout the treatment. After each heat treatment, the tresses were washed with shampoo (Charles Worthington Brilliant Shine® Shampoo, PZ Cussons (UK) Ltd, Stockport, Cheshire, UK). Shampooing followed a standard protocol. One milliliter of shampoo was applied to each tress. The shampoo was twice massaged into damp hair for 30 seconds, followed, each time, by 30 seconds rinsing under warm tap water. The cleaned tresses were air dried, and then put back into the dessicator. The treatments were repeated 12 times. Each tress, therefore, was heat treated, in total, for 60 seconds. Treatment with straightening irons—repeat dosing experiments with “wet” and “dry” products. In repeat dosing experiments, tresses were dosed and heat treated as above, but after cooling for one minute, the products were reapplied. This had the effect of building up the pro- tective layer created by the formulations. The tresses were dried for two minutes after the product was applied and then heat treated, again, for fi ve seconds. Product application and heat treatment were repeated three times before washing the tresses with shampoo. The cleaned tresses were air dried and then put back into the dessicator.