Fire cupping involves soaking a cotton ball in almost pure alcohol. The cotton is clamped by a pair of forceps and lit via match or lighter, and, in one motion, placed into the cup and quickly removed, while the cup is placed on the skin. Fire heats the inside of the cup and a small amount of suction is created by the air cooling down again and contracting. Massage oil may be applied to create a better seal as well as allow the cups to glide over muscle groups (e.g. trapezius, erectors, latisimus dorsi, etc.) in an act called "moving cupping". Dark circles may appear where the cups were placed because of rupture of the capillaries just under the skin. There are documented cases of burns caused by fire cupping.