Final answer:
To create volume during a blow dry, aim the air from the roots upwards using a round brush to lift the hair and a narrow nozzle to concentrate airflow.
Step-by-step explanation:
To create volume while performing a blow dry service, you should direct the air from the roots of the hair upward and in the opposite direction of how the hair naturally falls. To achieve this, use a round brush to lift sections of hair at the roots and then aim the blow dryer's nozzle at the roots, applying warm air to create lift and volume. As you move the round brush through the hair, continue to aim the airflow up the hair shaft to the ends, following with the brush. This technique uses the principle that airflow can manipulate the shape of the hair by pushing it in the desired direction and setting it in place. Think of the effect similar to pursing one's lips to blow out a candle at a distance, which demonstrates how airspeed can be controlled by changing the radius of the tube, or in this case, the nozzle of the blow dryer. The narrower the nozzle or radius, the more concentrated and effective the airflow.