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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 styli...

It's fairly common to have hair that is porous on the ends, but not at the roots. That means different parts or your hair require rather different care. How easily your hair becomes porous with just normal wear and tear and weathering depends on a lot of things. In fact, the kind of porosity your hair accumulates can be very different from person to person. How can the ends of your hair become porous? The ends of your hair are the oldest - they have had the most time to accumulate damage. While you up to 11 layers of cuticles covering your hair, if your hair is long there may be few layers left on the ends.  Brushing, combing, detangling, sleeping, wearing hats and collars, blowing around in the wind, wearing ponytails and braids and barrettes; these activities cause cuticles to chip or break away completely. Even more dramatic is over-washing the hair (especially if using strong or concentrated detergents), bleaching, highlighting or lightening the hair, permanent dyeing the hair ...

First off -  think of your hair not as a fiber like yarn because hair is more complex. Think of the inside of your hair like string cheese - protein which is flexible and retains water - it will swell when wetted. Then think of the cuticle as though you glued several layers of tiny, overlapping shingles to the outside of the cheese. You've used proteins and amino acids and lipids (fats) to glue all this together. It's flexible - but it's also prone to damage because proteins and fats do break down. Your hair's porosity is probably not the same at the roots as at the ends, the ends are usually more porous. "Pores" are openings in the cuticle layer(s) - whether they are chipped or torn cuticle scales (imagine torn or ripped-off shingles), or cracked, shrunken and fused, or simply not glued down very well. Any of these situations leads to a less-protected hair cortex - which means your interior of string cheese will dry out more quickly. ©Science-y Hair Blog 2013...