The level of heat required depends primarily on the density and general condition of your hair. If your curls are damaged, start with lower temperatures - around 170 ° F. The maximum for you is 350 ° F. The rule here is that the less it heats up, the better the condition of the hair. Thick hair can handle higher temperatures - up to 400 ° F or even 455 ° F. Tourmaline Ceramic Flat Iron can handle this level of heat. And relatively healthy medium hair needs an average temperature, between 300 ° F and 370 ° F.