To lock in the keratin in a Brazilian blowout treatment, stylists often use a blow-dryer and a hair straightener. The classic Brazilian blowout consists of very tight curls that are very smooth because the natural protein in hair acts like glue to hold the curl pattern. Hair fibers are made up of two parts: a central core and surrounding sheath. The core of the hair fiber is called the medulla. It contains the blood vessels, nerves, and pigment cells that give hair its color. The outer layer of the fiber is called the cuticle. It covers the medulla and is only one layer thick. The outside surface of the hair shaft is flat but has tiny holes called portholes. These pores allow water to escape while keeping out dust and pollutants. The type of hair oil or conditioner used during the Brazilian blowout will depend on the texture of the hair. For example, if the hair is fine and tends to be dry, some stylists may choose to use a moisturizing product before applying the blow-dryer. Otherwise, the heat from the dryer could damage the hair shaft.