D.) Less-than-thorough flat ironing. Using an average flat iron heat setting of 380°-410°F (193°-210°C), take small sections and meticulously flat iron until hair is silky. If hair is extremely fragile or compromised, start at the lowest setting on your flat iron and gradually move the temperature up until the hair gets easily silky. Concentrate at the roots, taking just enough passes until the hair is SILKY. All hair is different. In some cases there may be a bit of extra residue left in the hair. If so and the client desires, hair can be shampooed and conditioned at any time after the treatment, either in the salon or when the client gets home.