Thursday, March 6, 2014

Managing Elasticity and Porosity in Hair

Managing Elasticity and Porosity: "How To" and a little of the science behind it.

Elasticity is a hair character or property that overlaps with porosity. Human hair is elastic - it stretches a little. It stretches a bit more when wet than when dry when it is well cared for. If we over-stretch our hair, it will be damaged. But hair that stretches rather than breaks is a good thing because it's still there to protect our heads.©Science-y Hair Blog 2014

When hair is dehydrated, it loses it's elasticity, its "stretch." Think of leather or rubber or wood left in the sun and wind for a long time. It becomes dehydrated, loses it's flexibility and becomes brittle.

When hair is porous, it loses water more rapidly than is good for it. Hair can be porous because it has been out under the sun a lot, as a result of frequent washing or wetting or lots of brushing, from hair dye or highlights or swimming pools or chemical relaxers or permanent waves or high heat styling, from daily wear and tear or abrasive styling products.

If hair loses water too quickly, it becomes dehydrated. Dehydrated hair is less elastic. Elasticity, porosity and your regional weather are closely related. Even the healthiest of hair gets dehydrated when the air is very dry.

We need to define hydrated hair. Hydration for this purpose means containing adequate water. Hair is more hydrated when the air around it is humid because hair takes up water from the air around it. Hair is less hydrated when the air is very dry.

Porosity works into elasticity and hydration thus: The more "weathered" your hair is as a result of length (more time exposed to the elements), sunlight exposure, mechanical damage (brushing, styling) heat exposure, chemical exposure (peroxide, ammonia, pool chlorine, salt, acids and alkalis), the more porous is probably is. Especially on the ends.©Science-y Hair Blog 2014

Porous hair readily gains and loses water to the air around it because it is no longer protected by a tight seal of cuticles.

Because porous hair hydrates and dehydrates easily, it is difficult to maintain good elasticity. It is simply too weathered.©Science-y Hair Blog 2014

Elasticity in all hair helps prevent breakage when hair is manipulated - detangled, styled, slept on. Good elasticity in wavy and curly and coily hair helps support a strong wave pattern that returns when manipulated. Elasticity is part of the equation that helps reduce breakage.

One thing I have seen in the process of doing hair analysis is that hair often has normal elasticity when dry, but low elasticity when wet. Most of us know that wet hair is more fragile because it stretches more and because has extra friction between the wet strands. But I was surprised by this result. So I tested some people's hair I know to be very healthy and well cared for and got a "normal" result. I'm finding that low wet elasticity and normal dry elasticity correlate with hair that needs extra help staying hydrated - keeping the right amount of water in the hair.

So how do we keep our hair hydrated? Here are some simple ways to keep your hair hydrated to improve elasticity and manage porosity. It's not difficult to understand when you know some of the science behind it and when you pay close attention to your hair's response to these things. Nothing matters more for hair care than paying attention to how your hair responds!

1) Prevent swelling and dehydration and friction that occurs in wet hair and during washing.

Your hair has its cuticle layer which appears like 4 to11 layers of thin fingernails. The cuticles overlap like shingles or tiles on a roof - keeping water out when they are well intact. Cuticles are linked to each other, making this entire outer "cuticle shell" brittle. It really is like shingles on a roof - it can cover and even turn corners on hair - but it cannot increase in girth and still maintain integrity. 

Cuticle shown in yellow, endocuticle in blue,
cortex in red.

Turquoise arrows at left show the direction
of force as the endocuticle swells in water.

The layer beneath your cuticle, the endocuticle can swell a lot in water. If your hair is all lower porosity - the water doesn't get to this layer very easily. But when and where your hair is normal porosity to porous, water can get to this layer and it swells with water. The stress of hair-washing comes from the swelling layer beneath a non-swelling layer. As the expandable endocuticle swells beneath the cuticles, it increases in girth and exerts force outward, on the cuticle shell. As a result, cuticles are strained and stand away from the hair. In this state, they are more easily broken off. And so you have protein loss resulting from broken cuticles! Cuticles in this vulnerable position break from rubbing on other hairs, from wet combing or detangling while wet.
This is a porous area in a hair in water. The cuticles
are pushed out from force beneath as the endocuticle
swells with water. In this position, the cuticles are
more vulnerable to chipping and breakage which
causes loss of protein from the hair and further
increases porosity.

I'll add that shampoos which are too strong because they contain strong detergents or because they contain too high a concentration of detergent, and often acids like vinegar and bases like baking soda or soap bars tend to make hair swell more rapidly than plain water. All the more reason to pre-treat your hair!
This is a porous hair swelling rapidly in baking soda
solution. Not all hair reacts this violently.

How to prevent this:

- Pre-shampoo penetrating oil treatments
- Pre-shampoo conditioner application

Of these two options, the pre-shampoo penetrating oil treatment is the best-studied to address the swelling and protein loss and the "waterlogging" of too much swelling in water. Coconut oil has the best record for addressing these problems effectively, especially in bleached and damaged hair. But other oils may be similarly or adequately effective if coconut oil is too heavy for your hair or irritates your skin.

Leave a pre-shampoo oil treatment on for at least a few hours. 8 hours is the amount of time used in the study I'm citing below. Read more at the end of this post to find out how a pre-shampoo oil treatment works to protect your hair from damage during washing.

Conditioner before washing doesn't deeply protect the hair from swelling, but it does protect the hair from some of the water hitting it and occupy the detergent in a shampoo.  Cetrimonium bromide is an exception, it has been demonstrated to penetrate beyond the cuticles.

2) Prevent water loss from hair the rest of the time.
There are 2 ways you can do this, and you can do both at the same time, it involves products left in and on the hair.©Science-y Hair Blog 2014

A)  Water-soluble (non-oily) films that are flexible, invisible and yet water-protecting
B)  Water-insoluble (oily) films that slow water loss because they are not penetrable by water - oils and leave-in conditioners

Water soluble films can be formed by proteins, plant gums like flaxseed or okra, celluloses, pectin or carbohydrates, panthenol, hydroxypropyltrimonium honey. If you were to spread these on your skin, they would dry to a clear film. They would not be impenetrable to water - for example if you sweat, your sweat would pass through and also wet the film. These films act as a barrier to excessive water loss. Hydrolyzed proteins are water-loving and slow the evaporation of water from your (dry) hair. Not everybody's hair does well with proteins, but there are non-protein options in that list. This post has more about whose hair may do better with protein.©Science-y Hair Blog 2014

Water-insoluble films are provided by leave-in conditioners and oils you use on your hair. Oils on damp hair and leave-in conditioners on damp hair form a waterproof barrier to keep water from escaping too quickly. If your hair can tolerate oil without getting limp or greasy - oils can seal in the moisture on your hair and slow that moisture's escape into the air around it.

Oil on dry hair? That doesn't hydrate. That softens. It lubricates. Oil is water-free - so it can't hydrate or moisturize (not literally, anyway) and that's okay because hair there's a lot more to hair care than water.

3) Protect the hair to prevent water loss
Don't use high heat. Or at least not without a heat protectant.
Protect your hair from the full sun if you're out for a long time.
Protect your hair from dry, windy weather - wear a scarf or a hat you can pull your hair into. Tie your hair back if it is long so it does not blow around and use a little leave-in conditioner on it as you tie it back.©Science-y Hair Blog 2014

4) Deep treat
Protein treatments for people whose hair appreciates (or tolerates) protein
Deep conditioning for people whose hair needs extra softening and more flexibility

When you use protein or intense conditioner or both wither left on for 5-30 minutes with heat, more of the active ingredients interact with your hair and remain on your hair for a better result. Here is a link to Part I of a 2-part post about deep conditioning.

How does a coconut oil pre-wash do this? Coconut oil has been shown (using ridiculously expensive equipment) to penetrate beyond the cuticles thanks to its triglyceride content and small fatty acids. Coconut oil is attracted to the inner part of your hair. Coconut oil has a couple different effects - the first effect is not unique to coconut oil.
1) Blocks water from getting into the hair - like most oils do.
2) During washing, some coconut oil gets into the hair fiber as it is being washed. Because oil repels water, when it is introduced to the interior of the hair (which ordinarily attracts water), it makes the inside of the hair water-repellant so it swells less.
Less swelling means the cuticles won't be lifted up where they are easily broken off which means that all those proteins that belong to the cuticle won't be lost, your hair won't be waterlogged and I should add that your hair will feel soft and lovely after you wash it.

The effect is more obvious on damaged, porous and especially bleached hair (highlights, lightener, permanent color) and less obvious on lower porosity hair.

The effect of coconut oil is less if its applied to hair after washing than if applied as a pre-shampoo treatment.

What if I hate coconut oil? Palm kernel oil, babassu oil, sunflower oil and Ucuuba butter penetrate the hair and would be good substitutes for coconut oil. To a lesser extent, olive oil, avocado oil, castor oil, argan oil and other seed oils give you some of the protection from washing, but they may not have the same waterproofing effect on the interior of the hair as coconut oil. 
I use an oil mixture in my lower porosity hair and as far as I'm concerned, it's better in my hair than straight coconut oil which is too heavy for me and makes my hair a little rigid. Here is a link to a post about making pre-shampoo oil treatments work for your hair.
©Science-y Hair Blog 2014
In this post, olive oil did not protect the hair as long in chlorinated water as coconut oil and I suspect that is because the polar coconut oil is attracted to the hair proteins (it can get into the hair) in addition to forming an oil film over the hair surface.

You'll notice that conditioner protected the hair from the chlorinated water very well too - so if oil is just not your thing - a pre-shampoo application of conditioner, known colloquially as "condition-wash-condition" might do the trick.

AARTI S. RELE and R. B. MOHILE, 2003
Effect of mineral oil, sunflower oil, and coconut oil on prevention of hair damage. Journal of Cosmetic Science, 54, 175-192