Hair 101: How Hair Reacts Under Different Conditions

We’ve established that hair is made up of mostly protein, and that it requires moisture to maintain elasticity. We also know about the hair growth cycle and the rate at which hair grows. In this post, we’ll learn how hair reacts under different conditions.

Temperature: Hot or Cold

When you apply heat to your hair, some of the hydrogen bonds between the keratin fibres are broken. This temporarily loosens the curl pattern of the hair. Hair can be straightened by applying direct heat e.g. using a flat iron, or by applying indirect heat e.g. using a hair dryer on hair that is under tension. The curl pattern can be “reset” by wetting the hair.

Indirect heat (e.g. warm water or a hair dryer) not only loosens the curl pattern, it also opens the cuticle. An open cuticle allows the hair to absorb whatever is applied to it. On the other hand, the cuticle closes when hair is cooled e.g. rinsing with cold water or using the cool shot button on a hair dryer. Thus, when you want your hair to absorb something, indirect heat helps (e.g. sitting under a hair dryer when you deep condition your hair). When you want the hair to retain what it has absorbed, cool it down.

pH: Acid or Alkaline

In chemistry, pH measures the acidity of a substance on a scale from 0 to 14. A pH of 7 indicates a neutral substance. Acidic substances have a pH lower than 7; alkaline substances have a pH higher than 7.

Alkaline substances cause the hair cuticle to open. A good example of an alkaline substance is hair relaxer. The alkalinity allows the relaxer to penetrate the hair shaft and breakdown the hydrogen bonds that cause hair to be curly.

On the other hand, acidic substances cause the hair cuticle to close. You may be aware that many women rinse their hair with lemon juice or apple cider vinegar. The reason for this is that cuticle lays flatter due to the acid in those substances. When the cuticle is flat, the hair reflects more light and appears shinier.

Moisture: Wet or Dry

Image from derbycitynaturals.com

Wet hair is weaker than dry hair. Excess moisture in the hair shaft allows the hair to stretch, sometimes beyond its limit, and so the hair becomes weak and/or breaks. For this reason, you should not comb or brush your hair when it is wet. The exception to this is detangling while you have conditioner in your hair.

Your hair isn't elastic when it's dry - it is vulnerable to breakage, especially if you have fine or damaged hair. Many of us have experienced the sound of hair snapping like a twig. Always ensure there is sufficient moisture in your hair by using moisturising conditioners and moisturising lotion or leave-in conditioner.

Cuticle: Open or Closed

An open cuticle allows moisture and other substances such as proteins into the hair. Unfortunately, it also allows moisture to escape from the hair. A closed cuticle will not let moisture or protein into the hair shaft, but will keep moisture in. Use temperature and pH to:

• open your cuticle when you need your hair to absorb stuff;
• close your cuticle when you need your hair to keep stuff in.

Manipulation: Combed or Brushed, Down or Tied Up

We know now that we should refrain from combing and brushing wet hair. So should you only comb or brush your hair when it is dry? Well, dry brushing isn't good either. My suggestion is that you detangle/comb your hair with a wide tooth comb while you have conditioner in your hair. Although your hair will be wet, conditioner should make your hair slippery so that the comb runs through your hair easily and the strands come apart easily. This is the optimal time to comb your hair. Apart from detangling with conditioner, only comb or brush your hair when it is dry. Try other methods of controlling your hair, such as finger-combing and finger-smoothing, or wear low-manipulation hair styles like braid-outs, knot-outs and cornrows.

The pressure applied to hair strands when hair is tied up stresses the hair and causes weakness and damage at the point where the hair is tied. Avoid wearing pony-tails excessively. Consider wearing low-manipulation hair styles or letting your hair down every now and then.