Monday, October 19, 2009

Apple #416: How Hair Conditioners Work

I meant to choose a brief topic after that long entry about purple foods. But I was curious about how hair conditioners work, and I started reading about it, and of course since it's a question about chemistry and about how something works, the answer was not simple. But I'll try to break it down for you.

Lots & lots of hair products. But how do they work?
(Photo from Bongga Ba?!)

Here's the short version, about how hair conditioners work:

Hair conditioners basically put positive charges back into your hair so it doesn't get all staticky and fly-away and dried out.

If you want the nuts & bolts of how that happens, please read on.

Hair and the cuticle
  • First it's important to understand what's going on at the level of a strand of hair. Each piece of hair is made primarily of three layers:
  • The very center of the hair is the medulla.
  • The bulk of stuff surrounding that is the cortex. This is where the color lives and where moisture gets absorbed and retained.
  • The outer layer is the cuticle. It's kind of a sheath of scales that protects the cortex.

Diagram from Bigen

  • You definitely want those scales to lie flat. They help the moisture stay in the cortex, and if you've colored your hair, they help the dye to stay in the cortex. In general, they help protect the cortex from damage.

  • But when hair gets damaged -- from too much blow-drying, from too much coloring, or bleaching, or is broken by rough hair implements, etc. -- the scales on the cuticle stand up and leave the cortex exposed.

Damaged hair on the left, with cuticles standing up and exposing the cortex to breakage, and undamaged hair at the far right, with cuticles so smooth you wouldn't even know they're there.
(Photo from Hana Professional)

  • It doesn't take much to disrupt those cuticle scales. In fact, stripping away an electron or two from the cuticles -- in effect, changing their electrical charge from positive to negative -- can get them standing up.
Rubbing a balloon on your head strips electrons from the hair and transfers them to the balloon.
(Photo from Boing Boing)

  • Remember that trick from science class, when you rubbed a balloon on your head and made your hair stand up? When you did that, you were removing electrons from not just your hair, but from the cuticle. So while your hair was standing up, at the microscopic level, your cuticle scales were standing up, too.
  • That's not that big a deal because soon enough your hair finds the extra electrons it needs and settles down again.
  • But when you wash your hair, the soap in the shampoo is removing electrons. This is a bit more drastic than the balloon trick because the soap gets worked through all your hair, along the entire length of it.
  • Basically, what hair conditioners do is replace some of the positive charges that the soap in the shampoo has stripped away.
  • If you want to know how that happens, then it's time to start talking about the pH scale.

Positives and negatives on the pH scale
  • Maybe you remember those shampoo commercials -- I can't remember now for what brand. Was it Wella Balsam? -- where some lovely model assured us that this particular shampoo was pH balanced for healthy hair. What that means, essentially, is the shampoo is formulated to try to keep more positive charges in your hair even though you've put soap on it.

Farrah in a Wella Balsam ad. The copy doesn't say anything about pH balance so maybe it was another brand where they used to say that in the commercials. Anybody remember that?
(Photo from Angelic Ads of Farrah Fawcett)

  • The pH scale is a way of representing how much hydrogen is present in a solution. (pH means "potenz Hydrogen" or the potential for hydrogen)
  • The reason we care about this in the context of hair conditioners is that hydrogen ions carry a positive charge. The more hydrogen ions, the more positive charges there will be in the solution.
  • (Note to you chemistry purists out there, yes, I'm totally oversimplifying this.)
  • The pH scale goes from 0 to 14, with 7 in the middle. I think it would be much easier to understand if it went from -7 to +7 with zero in the middle, but then nobody asked me.
  • 7 is the magic number that corresponds to water. Water is considered neutral.
  • This is sort of counter-intuitive too, but anything with a pH lower than 7 has more hydrogen ions and therefore more positive charges. Anything higher than 7 has fractional amounts of hydrogen ions and more negative charges.
  • The way the pH scale is usually expressed is not in terms of positive and negative charges but as acids and bases.

pH scale with some typical examples of things at each point in the scale.
(Diagram by the Apple Lady)

Shampoos and conditioners on the pH scale
  • As you can see from my diagram, soapy water is pretty far out there on the scale toward the basic side.
  • Soapy water is far more basic (or alkaline) than shampoo. If you washed your hair with bar soap, your hair would feel really dry and crackly and unpleasant afterward.
  • So the people who make shampoo put stuff in it to make it less drying than regular soap. The things they add are chemicals that are farther along the acid side of the pH scale, or things that carry more of a positive charge.
  • Even so, shampoo does have to have some soap in it to carry away the dirt in your hair. It also removes some of the natural oils and good moisture naturally present in your hair.
  • When shampoo takes away the dirt and the oils, it's also -- because it carries more negative charges -- stripping electrons from your hair and making the cuticle scales stand up.

Shampooing doesn't just remove the dirt, it also removes electrons and can make your hair staticky. Rinsing with hot water can worsen the situation, so it's best to rinse with lukewarm water.
(Photo from lifehacker)

  • So if you used only shampoo, your hair would still feel somewhat dry and it would tend to be staticky and fly-away.
  • Conditioners, on the other hand, don't have to have much soap in them. All they need to do is add moisture and calm down those cuticle scales.
  • So conditioners have more hydrogen ions, they have more of a positive charge, they are farther along the pH scale on the acidic side than shampoo. They're going to help your hair and its cuticle keep more of a positive charge, stay calm, lie flat, hold in the moisture.

Where hair conditioners, shampoo, soap, and hair relaxers fall, in general, on the pH scale.
(Diagram by the Apple Lady)

  • Generally speaking, shampoos fall on the pH scale between 4.5 to 6.7.
  • Most conditioners have a pH of around 2.5 to 3.5.
  • But there's no way for us consumers to know that. The manufacturers don't print the pH level on the bottle -- though it might be helpful if they did.
  • But knowing a few things about the stuff that goes into shampoos and conditioners will help you decide where your particular brand may fall on the moisturizes / dries out my hair -- er, I mean pH-- scale.

Shampoo ingredients

  • Alcohol makes a good cleaner, so lots of shampoos have it in there. But it does have a high pH and it will dry out your hair. Which is why most shampoo makers use cetyl alcohol, which is alcohol plus a fat. The fat helps retain moisture and makes it less drying than alcohol alone. But even cetyl alcohol has a high pH: somewhere between 6 and 8.
  • It's tough to find a shampoo that does not have cetyl alcohol in it, so if your goal is ultimate moisture, look for one where cetyl alcohol is farther down the list of ingredients.
  • Baby shampoos typically have a higher pH than regular shampoos. Some adults swear by the baby shampoos, but they are more alkaline and will dry your hair more than shampoos formulated for adults.

Yes, baby Virginia, your shampoo has a higher pH than adult shampoos.
(Photo from

Conditioner types and ingredients
  • If a conditioner promises shiny, bouncy hair, chances are it's an acidifier. These have pHs around 2.5 to 3.5. They'll close up those cuticle scales nicely without weighing down the hair. These are good for people with fine hair that leans toward flightiness.
  • Detanglers are also acidifiers, with pHs of about 2.5 to 3.5. These also shut down those cuticle scales, but some also add an another polymer that is designed to act like a protective coat over the hair.
  • Conditioners that promise to add moisture are often humectants. These attract and hold moisture. They may include botanical products, but not necessarily. Panthenol, one of the primary ingredients of Pantene, is a humectant. pHs of these vary quite a lot, but they fall in the 4 to 6.5 range.

Pantene makes a lot of different kinds of conditioners. But most probably fall in the humectant category.
(Photo from Budget Savvy Diva)

  • Conditioners that add proteins are called reconstructors. These are designed to strengthen hair. Since human hair is made of 19 amino acids, a lot of the reconstructors will try to duplicate the animo acid recipe that is present in the hair to get it to penetrate the cuticle and get to the cortex and stay there.
  • Believe it or not, there are some reconstructor conditioners that contain placenta (animal, not human). I couldn't find out what the pH of these is. But I'm so disturbed the placenta thing, I kind of don't care.
  • "Pack" conditioners tend to be thick and loaded with fatty acids, and they're meant to be left in for a long time. These are close cousins to the original conditioners, which were essentially lard, and they'll pretty much glue those cuticles back down to the cortex. These are intended for hair that's been severely damaged. If your hair hasn't been that damaged, these will make your hair feel too oily and weighed down.
  • There are also some hot oil treatments. Oils are not water soluble so they don't get a number on the pH scale. But because they're not water soluble, that means they won't rinse out of your hair very easily. Oil treatments are for people with really dry hair, or for people who have used hair relaxers -- which, you may have noticed, are among the most caustic substances that exist. (Hair relaxers is a whole other topic, but this page at Treasured Locks has some really helpful information.)

Home remedies to condition your hair
  • Vinegar is a surprisingly good acidifier / detangler. It's acidic -- I can't get used to thinking that acids are good things to put in my hair -- with a pH of 2.4. So it'll really help to counteract the alkaline soap action inherent in shampoo. Apple cider vinegar seems to be people's vinegar variety of choice. For tips on how to use a vinegar rinse, check out the Chagrin Valley Soap Company's page on using a Natural Vinegar Hair Rinse.
  • Mayonnaise makes a good reconstructor. Wash your hair with shampoo, glop on the full-fat mayonnaise, wrap your hair in a towel, and let it soak in for about an hour. Rinse in cold water, then wash your hair again with a very little bit of shampoo to get the smell out, and condition lightly once more.

Mayonnaise, homemade. Putting this in your hair will help add protein (eggs) and moisture (oil).
(Photo and recipe for homemade mayonnaise available from the One Messy Kitchen)

BBC, The Guide to Life, the Universe, and Everything, How Hair Conditioner Works
Killer Strands, Understanding Shampoo - through the pH scale
eHow, How Does Hair Conditioner Work?
Paul Decelles' Entangled Bank, The pH Scale
Nigel D. Purchon, pH
Bigen USA, All About Hair
Salonweb, Hair Conditioners
Howstuffworks, Home Remedies for Dry Hair
Apple Cider Vinegar Benefits, Properties of Vinegar
Making Cosmetics, Cetyl Alcohol Material Safety Data Sheet
Treasured Locks, Black Hair Care Tips, Style and FAQs
Would you like some placenta with that hair conditioner? Green Daily


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