How do I test the hairs porosity and tensile strength?
To check porosity, comb a small section of hair straight up. Hold the ends firmly with two fingers, while you slide the fingers of your other hand down the strands, from ends to roots. If your fingers meet resistance or if the cuticle ruffles up, the hair is porous. The more it ruffles, the greater the porosity. You can also spritz hair with water: if it absorbs the water fast, it’s porous. To test the hair’s strength, hold a single strand near the base with one hand, and below the mid-shaft with the other. (Don’t hold the very end, which is naturally weaker.) Then pull until it breaks. Dry hair should stretch about 20% of its length before it breaks. Wet hair can stretch 40 to 50% of its length before breaking. If the hair breaks before it stretches this much, it’s weak. Repeat the test on 2-3 different parts of the head. Visibly check the ends.
