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Curly Hair Basics


What is Hair?

Hair is actually a nonliving fiber made from a protein called keratin. Keratin, in turn, is made up of long chains of amino acids created from what are known as the COHNS elements: carbon, oxygen, hydrogen, nitrogen and sulfur. These chains are linked together end to end like beads and are also cross-linked together by what are known as side bonds. These bonds are responsible for the strength and elasticity of the hair strand of which they are a part.


Each hair strand is made up of three parts: the cuticle, the cortex and the medulla. The medulla is the innermost layer of the hair; however, not everyone has one and it is most commonly found only in thick, coarse hair. Since the medulla is considered unimportant when it comes to hair services, we’ll only be paying attention to the cuticle and the cortex.


The Cuticle

The cuticle is the outer layer of hair. It is not one solid layer, but instead is made of individual scales that lay against one another just like roof tiles. The cuticle of a healthy hair strand will lie flat and protect the inside of the hair shaft against 

damage, as well as keep moisture in your hair where it belongs. Learning how to keep the cuticle of your hair shut is one of the most important things you can do to keep your hair healthy, moisturized and frizz-free.


The Cortex

The cortex is the middle layer of the hair shaft (for many, it is also the innermost layer of hair for those who don’t have a medulla). The cortex itself is responsible for approximately 90 percent of your hair’s total weight; additionally, the natural color of your hair is determined within the cortex by a pigment known as melanin. The permanent chemical changes that take place in your hair due to permanent haircolor, texturizing, perming, straightening or relaxing take place within the cortex.


The pH Scale – What It Is and Why It Is Critical to Curly Hair Care

The pH scale is what we use to determine the acidity or alkalinity of a substance. The scale ranges in value from 0 to 14, with 0 being the most acidic and 14 being the most alkaline:

Pure water carries a pH of 7 or “neutral,” so anything below 7 on the scale is considered acidic and anything above 7 is considered alkaline. So why is that critical for curly hair? Remember when I said learning to shut your cuticle is one of the most important things you can do to keep moisture inside your hair shaft and help to keep the frizz at bay? Acidic solutions are what shut the cuticle and keep the hair from damage, while alkaline solutions open the cuticle to let anything invade the cortex. That’s why choosing the right products and learning how to use them properly makes all the difference in the health and appearance of your curls.


Here’s an example. Your hair ranges between 4.5 and 5.5 on the pH scale. Technically, that means even the act of putting pure water on your hair is damaging all by itself because water is naturally more alkaline than hair. That’s why you hear so much talk about “acid-balanced” shampoos and conditioners, or why rinsing with apple cider vinegar (pH value 3) or lemon juice (pH value 2) can be so effective. Acid-balanced solutions, when used while cleansing your hair, bring your hair back into balance and shut that cuticle back down!


While the difference between 5 and 7 might not seem like a big deal at first glance, it is important to note the pH scale is what is called a “logarithmic” scale: each change in number means a tenfold change in pH. So, according to the scale, lemon juice at a pH of 2 is actually 10 times more acidic than vinegar at a pH of 3. And that means water is actually 100 times more alkaline than hair. Looked at in that way, it all of a sudden becomes a very big deal indeed. Understanding how pH works and how you can manipulate it to your advantage will help you in keeping your curls healthy and frizz-free.


What is Hair Texture?

Simply put, your hair texture is determined by the diameter of the hair strand itself. Fine hair has the smallest diameter, coarse hair has the largest, and medium texture is somewhere in between. Your hair texture plays one of the most important roles in how you should care for your curls, not only through daily maintenance, but also when considering any chemical services such as haircolor or texturizing.


Let’s take a closer look at the different types of hair texture:


Fine Hair

Fine hair can appear very limp or flyaway and does not hold a style well. It frequently seems dry, when in fact it is quite often over-moisturized. It is very easy to over-process and is quickly damaged by chemical services if great care is not taken. Products with a lot of humectants and emollients should be avoided in favor of those with protein, which acts as a strengthener and gives fine hair the strength and structure that Mother Nature did not.


Medium Hair

Medium hair is what is considered “normal” hair, meaning it has a mid-range texture. It does not require any special considerations for chemical services and usually processes normally. Undamaged hair with a medium texture can generally support products with a wide range of ingredients, although it is usually advisable for those with a medium texture to avoid protein in penetrating products, i.e., conditioners, deep treatments, etc.


Coarse Hair

Coarse hair is much thicker and stronger than fine or medium hair, but typically does not bend and cannot hold a style well. It is also often dry and brittle, due to an overabundance of protein. Coarse hair is much harder to process and is often very resistant to chemical services. Products with a lot of protein should be avoided in favor of those with humectants and emollients, as protein adds strength to an already abundantly strong hair strand and can cause a dry, hard, “broom straw” effect.


To determine your texture: hold a single strand up to the light.


  • Does the hair strand look delicate, a bit insubstantial, somewhat translucent, and seem almost as if it’s “barely there”? If any of these characteristics fit, the hair texture is most likely fine.

  • Does the hair strand look thick, wiry, and sturdy? Does it seem substantial and strong, with a very definitive presence and a distinctive lack of suppleness? If so, the hair texture is most likely coarse.

  • Does the hair strand seem somewhat solid, but not overly thick? Does it have some substance to it, but is still fairly supple? If so, the hair texture is most likely medium.

  • Please remember it is quite possible to have hair of varying textures all over your head―texture isn’t always a “one size fits all” kind of hair property!


There is one exception to the rule and that’s for hair that’s been lightened or bleached. When you put bleach on your hair, you blow holes in the cortex that look just like potholes. It doesn’t matter how “healthy” your hair feels after your lightening service―that only means you’ve been what we call properly “reconstructed.”


Every time you get lightened, you need to have a protein reconstruction treatment to fill in those holes, no matter what your hair texture. If you have coarse hair, however, one good reconstruction immediately after the service will probably do the trick, considering you naturally manufacture an overabundance of protein within your hair shaft anyway. Those with fine hair should consider a series of treatments to keep their hair healthy.


What is Hair Porosity?

Porosity refers to the ability of your hair to absorb moisture and is determined by the state the cuticle of your hair is in. Porosity is a critically important factor in determining curly hair care since moisture is what shapes and defines our curls. If you don’t know your hair’s porosity, you won’t be able to make the best product and maintenance routine choices to maximize the amount of moisture your curls retain. The existing “curl classification systems” never seem to mention porosity in their categorization process. Odd, considering lack of moisture is one of the biggest causes of frizz, the demon of Curly World.


There are three different classifications of porosity:


Low Porosity

Low porosity is when the cuticle of the hair shaft is too compact and does not permit moisture to enter or leave the hair shaft. Hair with low porosity is much more difficult to process, is resistant to chemical services, and has a tendency to repel product rather than absorb it.


Normal Porosity

With normal porosity, the cuticle is compact and inhibits moisture from leaving or entering the hair shaft; however, it allows for normal processing when a chemical service is performed and will readily absorb and retain product properly formulated for this hair type.


High Porosity

Hair with high porosity, also known as “overly porous” hair, has an open cuticle that both absorbs and releases moisture easily. Overly porous hair processes very quickly and can be easily damaged if extreme care is not taken when a chemical service is performed. Although overly porous hair absorbs product quickly, it is often dry as the open cuticle does not allow for product retention within the hair shaft.


To determine your own hair’s porosity, grasp a hair strand firmly between your fingers. Slide the thumb and index finger of your other hand from end to scalp (opposite direction as for texture test). If your fingers “catch” going up the strand, or feel like they are ruffling up the hair strand, your hair is overly porous. If it is smooth, you have normal porosity. If your fingers move very fast up the hair strand and it feels exceptionally slick, you have low porosity.


Why Hair Texture and Porosity are the Keys to Understanding Your Curls

This is where the so-called “curl classification systems” can be problematic. If Type 2 is supposed to mean fine, wavy hair, what happens if you have wavy hair with a coarse texture and high porosity? Or you have tight corkscrew curls often wrongly categorized as coarse, but your hair is baby-fine (as are many with curly hair) with really low porosity?


If you have wavy hair and follow the routines and use the products normally suggested for this curl type, but your hair is actually coarse and overly porous, you are going to end up with hair like straw–plus, you won’t be addressing the problem of your high porosity, which blows product out of the hair shaft anyway.


If your corkscrew curls are fine and you load them up with the humectants and emollients often recommended for this hair type, your hair will end up a limp, stringy mess, assuming you can get the product into your hair in the first place. It just doesn’t work that way.


Now that you understand basic hair principles, let’s move on.


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