Whether you are relaxed or natural, the use of direct heat is a point of contention with most hair gurus. Some advise absolutely no heat while some will say heat is ok as long as certain conditions are met. The best way to separate out fact from the noise is to look at studies done on hair to see what works and what doesn’t.
We all know what heat damage on natural hair looks like, it is hair that does not curl back up and has lost some of it’s tensile strength so it breaks easily. With relaxed hair, heat damage is harder to see with the naked eye but it is generally hair that has difficulty holding on to moisture and breaks like crazy.
Heat damage on a microscopic level is characterized by either tiny cracks appearing on the hair cuticles or blisters/bubbling on the surface of the hair.
Blow Dryer* Damage
Blow drying is something I imagine that most the relaxed ladies among you don’t do that often, and if you do tut tut! If you are a natural 4a, 4b or 4c however, it’s difficult to get a really good press without first stretching your hair with a dryer but blow drying is actually the biggest culprit for tiny cuticle cracks which subsequently lead to breakage. The cracks form when hair cuticles which are full of water are dehydrated rapidly at high heat. A study into this type of cuticle damage asserts:
These observations indicate that cuticle cracking is not due to a thermal shock arising from rapid changes in cuticle temperature. It seems rather that cuticle cracking occurs because those outer cuticles sections lack elasticity to comply with the dimensional changes either of the swelling cuticle layers underneath or of the swelling cortex
In the case of blow-drying, the lack of elasticity in the outer cuticle sections will originate from rapid cuticle dehydration at high temperatures. Thus, it would appear that when hair is wet or dried at room temperature, all cuticle portions and the cortex contract in a synchronous manner. However, if during a water evaporation process [blowdrying] only the outer cuticle sections contract more rapidly than those cuticle layers underneath or than the cortex itself, cracking will occur