Heat and Coily Hair Structure:
One study conducted some decades ago by the National Center for Biotechnology Information, part of the U.S. National Institutes of Health, revealed quite a few interesting findings regarding heat and hair. I'll do a "long story short" summary of what I read, and down below I will cite the study. It explains that the "magic number" is 140 Celsius (which is 284 F). Those numbers represent the temperature when heat will modify the hair structure in a way that is irreversible. Any temperature that is above 284 Degrees Fahrenheit will cause damage to the hair structure. Any temperature below that temperature during this study caused little to no modification to the hair structure, and was reversible. One thing to note is that even the lower temperature was linked to progressive loss of free water (causing the dry hair battle).
Lets talk about what was found at the higher temperatures (284 F and above).
- Structural modifications were "profound and irreversible"
- Followed by a "change in the appearance of a folding of the cuticle"
- Gradual disappearance of the scale of the cuticle
- Elimination of bound water: causing a total degradation of the structure (at around 392 F)
In this study, findings encouraged a drying temperature (I'm assuming that means blow drying or flat iron heat) of 140 C. It explains that this temperature would be best because the moisture pick-up will be slower. I'm thinking that's because this lower temperature drying actually leaves some moisture in the strands. The hair may not be wet per-se, but will contain some moisture. Hair that contains moisture will not be vulnerable or sensitive to atmospheric humidity variations (you will avoid frizz).
I flat iron my hair approximately 4 times a year. No reasoning behind this. It takes a lot for my super coily (tightly coily), very springy, pretty thick hair to get straight. It takes about 3 hours to safely and properly flat iron my hair for it to last. After a few trials and errors, I find that my hair requires serum and/or oils to help avoid quick reversion back to coily. I also found out that my hair requires heat over 350 F. Trust me, I've tried the lower heat settings, and realized that I may as well not even bother to flat iron my hair. My hair quickly reverts (while I'm still flat ironing it) if I use temperature under 350 F. Under 350 F, my hair won't even lay down properly. I go slowly with the flat iron and that doesn't lay it down. I do 3 passes with the flat iron (which I don't want to do), and it still doesn't lay down. I have to do 350 F or more to get straight results.
Lots of people ask me what temperature they should use to flat iron their hair. It's all about trial and error based on the physical properties of your hair. I started my flat iron sessions at a low temperature, and worked my way up to higher temperatures while watching the outcome. That's the best way to determine the safe/effective setting to flat iron different hair textures/densities/thicknesses.
Some signs of dryness are:
- Ashy or dull looking hair
- Limp hair that does not respond to styling tool or products
- Easily tangles at the ends (or roots)
- Hard/Dry feel
I notice the difference right away. My coils do not coil up, they will just lay limp and loose. This is not always heat damage. If coils still look limp after deep conditioning and co-washing (or removing product buildup with the proper shampoo), then it may be irreversible.
To me, this scientific experiment explains or defines what is known as "heat training". It basically says that if heat is continuously used at or above a set temperature, then irreversible damage to the hair structure will occur. I love that the study was able to reveal a temperature at which the damage was found to happen. I always wondered about that.
I will share some pictures of my coils before, during, and after heat use. I took these picture only because I noticed the changes.
To wrap this post up, I've come to understand a few things about heat and coily hair. I think that the hair that is most difficult to get straight via the use of heat, probably should not use heat often. Looser coil patterns can use less heat to get their hair straight, and that's definitely to their benefit (although, once they set the temperature anywhere above 284 F, --even 300F, they will experience damage over the long run).
|Wash N Go Attempt (eco styler gel used) After Flat Ironed Hair: Dry & Undefined Coils|
|Mayo/Avocado/Olive Oil/Honey Deep Conditioning Treatment Applied|
|After Deep Conditioning Treatment Rinsed Out: Coils Shiny and Defined|
|Hair 100% Dry: No Curl Definer Used|
|No Curl Defining Product Needed: Deep Conditioning Restored Moisture|
Since I've got to crank up the heat to make my hair straight, and do a few passes to make sure it stays straight, it wouldn't benefit my coils to do this often. According to this study, even 1 or 2 times using the flat iron will cause irreversible damage to my hair because my temperature setting is at 400 F! I can believe it. I'm pretty sure that's why some coily hair girls notice a "loosened" coil pattern over the years (that and a few other reasons).
WHAT'S YOUR EXPERIENCE WITH HEAT USE?
The Study that was cited in this post: