Friday, June 15, 2012

Hair Porosity: How To Measure (Sort of)

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

Why the Float Test Is Inaccurate:©Science-y Hair Blog 2013
The "float test" for hair porosity is one in which you try to float a strand of hair in water. It is supposed that a porous hair will immediately begin to absorb water, become heavy, and sink. But there are some flaws in the design. See this post for an update to the float test.
  •  First of all is surface tension of water. The molecules at the surface of water stick together where air meets water. Like a "skin" on the water. If you place a light-weight object on the surface of the water gently, it will float. You can make sewing thread and even dry sand float on water this way. So let's say you have a very lightweight, but porous hair and you drop it in a glass of water. The surface tension may well override the weight and porosity of the hair strand and it floats - even after many minutes have passed.
  • Second - specific gravity. Hair and water have a similar specific gravity. Things of similar (or lesser) specific gravity to a given liquid will float in that liquid. Dry hair is buoyant in water - like ice or driftwood.
  • Third: What is on the hair? Is the hair heavier due to the weight of a product? Is that product repelling water? Is that product a wetting agent (like hair conditioner) which will cause the hair to become wet more quickly and sink?
Arrows show where the cuticle has chipped away due to sun
and friction.
See what I'm getting at? Too many variables. And for porosity, your own observation is going to take many variables into account which will give you plenty of relevant information.

One of the most accurate ways of measuring hair porosity is using gas sorption to determine total pore volume (holes in the surface) - which is expensive and absolutely not do-it-yourself. It measures how much of a given gas can be taken into hair - hair which has more pores will take on more gases. Hair can also be examined under a microscope to determine how much chipping, wearing away, or lifting there is in the cuticle. This is purely visual. Weight of water taken on by a dehydrated hair sample could be measured, if you had a bunch of other samples to compare to for reference material. All impractical!©Science-y Hair Blog 2013

Most very accurate methods of measuring porosity are not accessible to most people and that's okay because it is really easy to determine. This post has more information about hair porosity, some of which is about to be repeated.

Porosity matters because it determines how much protection your hair needs (what you'll apply to it) and how quickly it will lose water. It also determines how well or quickly your hair takes color. Porous hair loses water more quickly than hair which is not especially porous. Dehydrated hair (like dehydrated string cheese) is less pliable, breaks more easily, has less shine and does not hold a shape (like a curl or wave) neatly.

How to Determine Your Hair's Porosity: This is something you learn from studying your hair by running your fingers over a hair strand, observing shine or reflectivity, how hydrated your hair feels on a daily basis, and your hair's response to products. Learn by studying!? Yes, this is sensory and multi-faceted. You are the best judge of your hair's porosity - here are some hints.©Science-y Hair Blog 2013

This hair is fairly healthy - the cuticles are intact
and fit tightly over one another - not very porous.
Not-porous hair: Your hair is not porous if it is very shiny. Try folding a wide strand of clean hair (no styling products) over a finger - does it shine brightly? If you do not heat-dry your hair with high heat or use curling or straightening irons, do not spend much time in the full sun, do not brush your hair often or do not color or bleach (highlight) it - it's probably not very porous. If your hair does not absorb oils and conditioner and becomes greasy or limp easily, it's probably not very porous. Not-porous hair takes permanent waves (perms) poorly and resists chemical straightening and hair dye. Not-porous hair does not tolerate lots of conditioner or oil - it will become oily-looking and limp (although this variable overlaps with the diameter of your individual hairs quite a lot). Not-porous hair will not dramatically change with more conditioner or deep conditioners because it is not losing a lot of water under most conditions - its cuticle fits snugly and there are not a lot of cracks and chips. Products (hair conditioners, oils, styling products) do not seem to "soak in" to not-porous hair. Not-porous hair is easy to maintain in a healthy condition. There is no reason to try to make it act more porous so that you can apply products to make it softer. Hair products like conditioner are actually designed to make hair behave as though it is not-porous. So if this describes your hair - life is good!©Science-y Hair Blog 2013

This hair is showing normal porosity - the cuticle looks
like shingles on a house - you can see this at the edge of the 
Normal-porous hair: It shines, maybe not quite as much as not-porous hair. It perms and takes color as expected. Your hair can be normal-porous even if you use some heat on your hair (low-heat diffusers). Normal-porous hair does not become oily-looking with reasonable amounts of conditioners or oils. Normal-porous hair may have times when it feels a bit dry, or not dry at all and it is easy to make it feel "not dry" and soft with hair conditioner and gentle care. You perceive some "soaking in" of hair products. You probably have had some exposure to the full sun, possibly chlorinated swimming pools. Your hair may be not-porous near the roots and normal-porous further down and therefore respond differently to conditioners in those two areas, which is why many people condition their hair from the ears, down. If you run your fingers up and down an individual hair, it feels mostly smooth. This normal-porous hair has cuticle scales which look like shingles on a roof. They overlap and don't stick up much.©Science-y Hair Blog 2013

A kink in a hair where it is both narrowing and twisting.
Porous hair: If you run your fingers up and down a hair strand, it may feel bumpy and uneven due to kinking, or to damage. Quite porous hair does not shine much and though it may have some gloss, it's not "reflective" or brightly shiny. It will seem to absorb hair products of any kind, tends to feel dry most of the time and you have a difficult time getting it to feel soft and pliable. It may lose dyed hair color rapidly because of the porosity.

  • Kinking and porosity: Kinking in hair creates an uneven surface and it may be difficult for cuticles to lie flat and smooth when the hair shaft they're attached to is widening and narrowing or torque-ing (twisting). Any uneven surface accumulates more friction than a smooth surface. If a cuticle sticks out a bit, it is likely to be chipped or broken off. Kinking hair can be more vulnerable to increased porosity when exposed to daily wear and tear because it suffers more friction from everyday living than non-kinking hair. This photo (above, right) shows a porous hair with kinking (a kinky, curly hair). Kinking can occur in any hair - straight, wavy, or curly. Not every person with kinking hair will have porous hair - and you can look at people in your family to see whether you inherited hair that tends to be extra-thirsty or not. There are many variables involved, but this is an important one to know about because people with kinking hair usually need plenty of "slip" in conditioners to reduce friction. I'm fascinated by the patterns and frequencies of kinking in hair, so I digress...

Arrows show "lifted" cuticle which is one type of pore,
making this hair moderately porous. This is a little tricky to 
photograph. Lower down there is an indentation which
is where a piece of cuticle has broken off.
  • Environmentally porous hair (damaged hair): Hair becomes porous with high-heat styling tools (curling/straightening irons, hot rollers, blow dryers on high heat without diffusers). Hair becomes porous with a lot of sun exposure or a lot of swimming in chlorinated water or salt water. Bleaching or highlighting immediately make hair more porous - up to 30% more pores than prior to bleaching - this is similar to the increase in porosity from 200+ hours of direct sunlight exposure. Brushing hair a lot, shampooing frequently, regularly wearing barrettes or tight clips, ponytail holders all can shear away pieces of cuticle or entire scales, leaving gaps. Friction of a handbag over hair, hair tucked into a collar, under a hat and so on also shear off cuticles. 
This hair has substantial sunlight, chlorine and friction 
damage. Notice you can barely see any cuticles. This
is not bad focus in the photograph, it is hair damage. This hair
is quite porous.

Porous hair usually takes on dye, permanent waves and chemical straightening quickly. And loses dye quickly. Porous hair loses moisture easily. The hair in this photo is porous because of all the sunlight and brushing and chlorine it was exposed to over many years. In this case, most of the cuticle has been sheared off and is not visible. It has a difficult time retaining moisture.©Science-y Hair Blog 2013

Hessefort, YZ, Holland BT, Cloud RW, 2007. True Porosity Measurement of Hair: A New Way to Study Hair Damage Mechanisms. Journal of Cosmetic Science

Chemical and Physical Behavior of Human Hair 
Robbins, 1994. 3rd Ed. Springer-Verlag, New York


  1. WS,

    Can you test for porosity on heat (100% natural) damaged hair? I've read countless articles regarding porosity but I I'm still unsure because my hair has qualities of both hair and low. I have a question about hair tangling, matting and being DRY after washing. I pre-poo with oil, detangle with conditioner, shampoo and condition and deep condition. Once my hair dries after applying Giovanni direct leave in, Qhemet Biologics Burdock Cream and Jojoba, it is HARD, MATTED AND TANGLED. You would swear I never washed my hair. It is so dry and tangled knots become forming. All this on wash day. I believe my porosity is high from heat styling. What would you recommend to solve this problem? Do you think porosity is the issue or something else. I've read Roux Porosity Control Corrector & Conditioner can help. Do you think I should try that or do something else? I don't know what else to do and I'm very frustrated because my hair ends up breaking/shedding when I try to style.

    1. I think there is a lot going on here. As a very simple observation, porous hair tends to become glossier and smoother if you apply (but don't over-apply) an oil to dry hair that agrees with that person's hair whereas low porosity hair tends to get greasy easily from applying oil to dry hair. Low porosity hair can tolerate some oil, but it will go from glossy to greasy more easily.

      For oil pre-washes, you might experiment with oils like avocado or sunflower (unless you're using them already) and leave them on for 4-8 hours before washing. Sometimes coconut oil makes people's hair hard or brittle or tangly and matted, so if you've been using coconut oil for your pre-poo, you might try one of these other oils to rule out any problem with coconut oil and your hair.
      I have heard of people getting "hard" hair from Giovanni Direct Leave-In - though it might be okay if it were applied and then water was added (pour water over hair or step under the shower spray). The Qhemet product - I'm not sure. I have a partial ingredient list from their website and some ingredients that might cause problems are the Wheat (whatever form it's in) and oatstraw, MSM and glycerin. Any of those could have an unpleasant effect on your hair. They are good ingredients, but they aren't necessarily good for every head of hair and every climate.

      If your hair is porous from heat styling, the Roux Porosity Control Corrector might be helpful. It has amino acids and humectants and detangling ingredients. If your hair is not especially coarse (wide, strong strands that are easily felt between the fingers) it may tolerate something like Ion Reconstructor or Ion Effective Care Treatment (both with hydrolyzed keratin) or Shea Moisture Noni & Monoi Smooth and Repair Rinse out conditioner also.

      If you have been using lots of products that soften (emollients - oils, leave-in conditioners etc.) and no protein and you're getting breakage, then it may be time to try protein (Roux, Shea Moisture or Ion from above). If you get a good result from the protein, repeat it when that good result fades. Unless your hair is narrow (fine or medium-width strands, silky) and porous, it probably won't appreciate protein every single time you wash your hair.

      But you shouldn't be getting tangled, matted, knotted hair on wash day. That seems to indicate that your hair is reacting badly to one or more products. Maybe try changing one or 2 products at a time. For example, if you were using a coconut oil pre-poo, try switching to avocado or sunflower oil and using all the same "other" products.

      If there is no change with that, then try switching the Qhemet product for one without glycerin and wheat and so many herbal ingredients - you could mix some oil into a thick rinse-out conditioner if you don't want to buy a new product for this.

      See what happens. If there is no change, or even if you get a bit of benefit from one of these changes, then is time to try some protein (or trying protein might be the first change you make - whatever you want to rule in or out first).

      It's not always easy to be this methodical, but over time you develop an "if this, then that" mental flow chart and being methodical about making changes helps you figure out the effects of individual things.
      Good luck!

  2. If the hair floats is it damaged? If the hair sinks is it strong?

    1. See the end of this post (copy and paste)

      Usually only highlighted or damaged hair will sink if you follow the instructions at the end of this post. If there is hair gel or conditioner on the hair, you're likely to get an off result. But even hair that sinks and is porous can still be strong if it's well cared for.

  3. Thank you so much for this! I was fairly certain my hair was porous because my mom (former hairdresser) would always say it drank the color up very quickly when she colored my hair. She'd have to use tons of color even though my hair wasn't very long or thick. This confirms it. I definitely feel those bumps and kinks you talked about when I run my fingers over a strand of hair. I need tons of slip in conditioners, too. I haven't actually found a non-silicone one that will do the trick, but I'm trying to stay away from the silicone anyway. My hair also drinks up hair products and my hair doesn't feel like I've put anything on it. I have to put tons and tons of gel on my hair for it to form a cast. The only thing it doesn't absorb like that is oil. That makes my hair pretty greasy.

    I just discovered also that everything I'm using has protein in it. I bought stuff before learning enough. I stretched one of my hairs just now and it barely stretched and then broke. Too much protein, right? But still, super porous hair.

    Any advice for me? I know I can't repair my hair, but is there anything I can do to help it behave better?

    1. I use Giovanni Smooth as Silk conditioner and absolutely love it! It is silicone free, super moisturizing, and very slippery. I use it in the shower and just leave some in so I don't have to add another conditioner. Hope this helps!

  4. I take back what I said about brittle hair. I think I was pulling to hard. Tried on a different strand and it stretched and stretched and stretched and didn't bounce back.

  5. WS, are there different hair types (regarding porosity) with ethnicity? I read that Asian/African/Caucasian is different in the size and shape of the cortex, but does this apply to porosity as well?


    1. Hello RhiannonB,
      I have some of the same information in my books and articles I've read. Asian hair is supposed to be the most round in cross-section. For people of African descent, hair is often the most elliptical - oval or flattened ovals in cross-section. Kinking represents rotations of the hair shaft around its own axis and sometimes coincides with more- flattened areas. In my experience, I see the most kinking in wider hairs than narrower hairs - even from the same person's scalp. Hair from people of European, Indian, Russian, etc. descent tends to be elliptical, with varying amounts of kinking.
      Porosity - how much water hair takes up and loses has a lot to do with how often you wash your hair, how much sun exposure you have, what other exposures your hair has (salt water, chlorine, highlighting, heat-styling), whether you take steps to keep hair hydrated... Genetics has a lot to say about porosity too. Some people have really robust cuticles (often in wider/coarse hair) that keeps their hair low-porosity no matter how they abuse it - for real - some people can wash their hair frequently, dye it, and it's still low-porosity. Others have more delicate hair that is damaged more easily by normal wear-and-tear.
      Some people's hair is slippery/silky or water-repelling and just never seems porous, even if it accumulates some damage. And some people's hair loves to soak up oil and conditioner, even when it's healthy - and more so if its slightly damaged.
      Since I've been doing hair analyses - I've learned that generalizations are really difficult to make. For some people, kinking in hair represents areas where friction and pressure are not evenly distributed - and that will cause localized porosity. But not for others.

      The number two thing that impacts hair porosity (genetics is number one) is how you care for your hair. When people space out their washings as much as possible or practical, take care to keep hair hydrated with whatever treatments are appropriate, handle their hair gently, don't use high heat styling, hair tends to be lower porosity.

      For size: I don't know that generalizations can be drawn about hair width for entire continents of people because there is a lot of genetic diversity from region to region. But for hair width, you can definitely make generalizations: Coarse (wide) hair has a greater amount of cortex compared to cuticle. Medium or fine hair has more cuticle relative to the cortex because of the narrower width.

  6. I'm a Black girl and I am trying to determine my porosity. I have kinky curly hair and I have trouble moisturizing my hair because the moisturizers I use never "sink in" to my hair

    1. Hello DD,
      If you want to use the float test - use the tips at the bottom of this post (Make the Float Test More Accurate), followed by how to interpret the results:

      For hair that products never seem to sink in, the "Low Porosity" post might have some useful information:

  7. I am a black girl with kinky curly hair who's trying to figure out her porosity. I have trouble moisturizing my hair because the products sit on top of my hair rather than sink in but maybe it's high porosity. It seems like I never get something that will thoroughly moisturize my hair and penetrate it and leave it soft. I have asked around and only get products recommended but I'd rather not waste more money and just want a method to help.

  8. My hair is wavy, but I prefer to wear it straight. So either I use a blow drier or, if I air dry, I tie it on a ponytail. So here is the question: what's more damaging for hair? Heat or tight ponytails?
    I had highlights two months ago and my hair is breaking like crazy ever since. I've been applying masks, coconut oil and applying thermal protectors before drying, but I'd like to know which styling is less damaging.
    Finally, a suggestion for a blog post: do thermal protection products really help to protect hair from heat? How well?

    1. Hello Camilla, this late reply is the result of my comments section not wanting to load lately. I'll describe the damage that occurs with each, and you can decide which worries you. High heat used to take your hair from wet all the way to dry is damaging to the cuticles on the hair surface. They chip and crack - and that makes them brittle and likely to break. Broken and missing cuticles can make hair more porous over time and also contribute to a dull look and dry feel. Tight ponytails might stretch hair somewhat if they are extremely tight and tighten while the hair dries and shrinks a little. There can be breakage where the ponytail elastic is - so it's best to use a wide or flat elastic with no rough surfaces or metal.
      I have a list of effective heat-protectant ingredients (and products containing them) in this blog post (the link may need to be copied and pasted into your browser). Best wishes - WS

  9. What type of microscope would you recommend buying if I wanted to get a close up look at my hair strands and see if the cuticle layer is in intact or not or in between?

    1. I use a transmitted light microscope that shines light through from beneath. The alternative is a "field scope" that uses an external light source - from the side or above. Monocular scopes (one eyepiece) are adequate. You need at least 100 to 200x magnification. I use 400x magnification.