Just as blacksmiths empty their incendiary leather instrument i.e. hapar or bhanga once and then fill it with air, similarly the Kapalavati practitioner should quickly fill the breathing apparatus with air through the nostrils and immediately deflate it i.e. quickly inhale and exhale while sitting in Padmasana as in picture. Exhalation will be much more forceful than inhalation. In this condition, the lower abdomen will move in and out during inhalation and exhalation. Try to keep the spine, chest and shoulders as still as possible. The first student can practice 15/20 times as per ability and then with increasing ability can practice 50/60 times to 120 times per minute.

Bhadravaslokarahasya Rechpurau Sasambhramou.

Kapalavatibikhita Kaphadosa Vishoshini.

(Hattayoga-Pradipika - 2/35)