Curl Class 8: Porosity & Density

So this is the final Curl Class *sob sob* - me? I’m not crying! It’s just a hair in my eye! In this final class I’ll tell you a bit about two more properties of your hair: density & porosity!

Density

Density refers to the actual number of hairs growing from your scalp and partly influences if your hair is ‘thick’ or ‘thin’. It varies according to hair colour so blondes tend to have the highest number of strands followed by brunettes (black hair is brown - no hair is completely black unless artificially coloured that way) then redheads. I know you’re thinking ‘but redheads always seem to have such big bouncy hair!’ This is also true, because our clever body uses our strand thickness to balance out the density; as the strand number decreases, the thickness of each strand is increased¹. So whilst redheads may tend to have fewer follicles, their strands are coarser and vice versa with blondes who usually have fine hair but lots of it. Brunettes are in the middle so can have a mixture of fine and coarse hair (which is true of my hair). Alternatively they can have fine thin hair, coarse thick hair, fine thick hair or coarse thin hair.

Having less hair on your head also means that you have fewer follicles so produce less sebum. This and the difficulty sebum has traveling down the strand, means coarse afro hair ends has to be moisturised often to reduce breakage. Fine afro hair has to be cleaned (preferably with a conditioner) more often to prevent the build up of sebum on the scalp.

Tyra Banks has thin and fine hair (although you'll never really know as her hair is relaxed - I think!)

Solange Knowles has hair that is thick but a mix of strands so when straightened is 'normal'

Oprah Winfrey has voluminous hair when straightened or curly so has thick, coarse hair

Unfortunately for afro hair there is no easy way to determine whether it is thick or thin as it forms such tight kinky curls giving the appearance of having lots of volume. (Even some hair stylists don’t know, evident from the fact that in an episode of Extreme Makeover a hairdresser thought a woman’s natural hair was too thick so he cut it off in rows at the root! It was coily so of course it looked thick!) The only advice I can give is to learn for yourself (crap advice, I know) and you won’t truly know if you are relaxed, because afro hair isn’t made to be straight so will always look thinner when straightened. Zainab used to think her hair was thin when she was relaxed, but when she went natural found out she has A LOT of coarse hair.

Porosity

The last hair characteristic you should know about is porosity! Porosity is the number of pores located on your hair shaft. Remember when I told you about the scaly nature of the cuticle? (No! Well read it here then!) The scales can either lay parallel to the strand over one another or open up and expose the medulla. The more ‘open’ your cuticle is the more porous it is. This affects how well you can absorb and lose water and other helpful (or not so helpful) chemicals.

Low porosity hair finds it difficult to absorb molecules as the scales are closed, so when applying conditioner or creams it may seem to resist the product. To open up the cuticle and aid absorption you’ll have to leave the product on for a longer time and possibly use heat in the form of double (or triple) shower caps and hair dryers. But once the product is absorbed it’s locked in for good!

High porosity hair easily absorbs anything. Because the scales are open, products can easily pass into the hair shaft so the hair is easily moisturised. But this also causes the hair shaft to easily lose moisture as it leaves just as easily as it came in. Therefore high porosity hair will need to be moisturised more often to retain that soft feeling.

A damaged strand of hair with very high porosity

Straightened, relaxed or dyed hair is much more porous than natural hair as the disulphide bonds holding the layers of the cuticle down have been broken. This means they need to be deep conditioned more often to retain moisture and stop breakage – especially dyed hair if it has been bleached!^2,3 This also indicates that you won’t know your natural porosity state until you grow out the altered part of your hair.

Some people believe that you can find out how porous your hair is by placing clean hair in water and seeing if sinks or floats, however this is a myth. Even shampoo and conditioner changes the porosity of your hair (as does combing during detangling) and it changes from the top of the strand to the bottom and between individual hairs³. So how do you find out if your hair is porous? With an electron microscope of course! Wait… you don’t own an electron microscope?! Oh… well the other option is to just figure it out throughout your journey. (Once again, not amazing advice.)

Maz xx