The Other Entanglement

 

A year ago I wrote a blog entry which included  “entanglement” – a complicated quantum mechanics concept where multiple particles … never mind. (If you’re interested, go and look for the February 2021 blog “Schroedinger’s Bird ??????”.

This other entanglement is more easily understood. Why does hair tangle and how do you get it untangled?

When you look at hair under a microscope, you can see that the core of the hair is covered with cuticles. Think of them as being like the scales of a fish. Both the cuticles and the core of the hair are made up of keratin – helix-shaped protein molecules. The cuticles are covered with sebum, an oily substance which protects the hair from drying out. 

 

                                         A single human hair, showing the cuticles

Because hairs are not smooth, if two meet at the right (wrong?) angle, they can snag on each other. If hair is damaged, cuticles may be missing, torn, or more protruding, and the tangling will be worse. Not all hair is the same, of course. Hair ranges from fine to coarse in thickness, and from straight to curly. It’s not a simple problem to figure out what hair will tangle more. A head of hundreds of thousands of strands colliding in all directions is just the sort of knotty problem that mathematicians and physicists love to tackle. Some fine work done by Jean-Baptiste Masson, a brain imaging researcher at the École Polytechnique in France showed that, although curly hairs cross more often than straight, the angle at which the hairs meet is most important. Counter-intuitively, straight hair tangles more than curly. And what appears to be the most important factor is the diameter of the strands. Fine hair tangles more than coarse hair.

 How to Untangle Hair

 Less surprising than the study of what hair tangles most, is the result of work done by a team of scientists at Harvard. They found — drum roll, please — that untangling hair is best done by starting to comb close to the ends and then working your way up to the scalp.

You can also get some help from the magic of chemistry. There are dozens of commercial Detangling Sprays available. My favourite — based solely on the name — is this one:

 The name is based on the widespread myth in Southern Africa that elephants eat the fermented fruit of the Marula tree, get drunk on the alcohol, and rampage around, causing widespread destruction. And of course, what could be more effective at detangling your hair than a rampaging drunken elephant?

The active ingredients in detangling sprays are

• Oils. These replace missing sebum, making hair softer and less likely to tangle.
• Silicone. A substance with long molecular chains that bind to the surface of the hair and make it glossy, smooth and less likely to tangle.
• Acidifiers. Lowering the pH of the hair strengthens the hydrogen bonds between keratin molecules. This smooths and tightens the surface cuticles on each strand.
• Hydrolyzed Protein. Amino acids which are the building blocks of proteins. These help to repair damaged keratin, smoothing broken edges of the cuticles.
• Surfactants. These molecules have one part which binds to the exposed keratin, between damaged cuticles; the other end of the molecule is hydrophobic (repelling water) and creating a smooth thin film that’s easier to comb.

 Preventing tangles – Shampoo and Conditioner

Shampoos are detergents which do one simple job: remove dirt from hair. The dirt is caught up in the oily sebum and the detergent washes it away. Detergents are molecules with one end which is attracted to oil and the other end attracted to water. So one end binds to the dirty, oily sebum and rinsing with water washes away that dirty oil. Any detergent would effectively wash away the dirt. Soap, which is also a detergent, would do that. If you live in Vancouver, which has ‘soft’ water, soap should work quite well instead of shampoo. If you live in Montreal or Kitchener/Waterloo, which have ‘hard’ water, not so much. ‘Hard’ water has dissolved salts of calcium and magnesium, and soap reacts with them to form a deposit: “soap scum”. You don’t really want that coating your hair after you wash it; you need a detergent other than soap.

Some other considerations:

• shampoos are pH balanced – between 5 and 8. Outside of that range, the cuticles will not lie flat.
• The detergent must not be too strong. If it is, it will remove all of the sebum, along with the dirt, and your hair will end up too dry.
•  Shampoos always include a foaming agent. This has absolutely no use except to make the user feel as though the shampoo is working. If the shampoo doesn’t foam, people won’t buy it.

Even with a mild detergent, conditioners are helpful in replacing the sebum that’s been removed. How do conditioners work and what are their active ingredients? Conditioners are actually the same as detanglers, so they are just like that descrition above. Yes, you can use a conditioner as a detangler, especially the conditioners that are designed to be left on your hair and not rinsed off.

Final snippet: 2 in 1 Shampoo & Conditioners are great for saving time. You wash and condition your hair in one step, not two. But how do they work? How does the conditioner “know” that it should wait for the shampoo to remove the sebum before coating the hair? Clever chemistry holds silicones in suspension in a shampoo until the shampoo is rinsed away with a lot of water. So, during the shampooing the silicones are held in a sort of suspended state of animation. When the shampoo is washed out, the silicones are activated, coat the hair and leave it in good condition. The results can be pretty good, but still 2 in 1's can’t match the effectiveness of separate shampoo and conditioner.

 

Santa’s White Hair

Santa's hair and long beard are white as snow. But as a boy, his hair was probably a different color. Just like boys the world over, his head would have been topped with shades of brown, red, or yellow.

Hair color originates inside the skin on the head, where hairs are attached. Pull on a hair firmly and slowly until it comes out, and you'll notice a small white tube clinging to the end of it. This tube is a clump of cells that fit inside a narrow hole in your scalp, a hair follicle. Hair grows in hair follicles, and the cells that line hair follicles supply the growing hair with color.

A hair grows as cells are added to its bottom. These cells contain a strong protein called keratin, which gives hair its structure. Fingernails are made of keratin too. As more and more cells rich in keratin are added to the bottom of the hair, the older cells are pushed higher in the follicle tube, towards the surface of the scalp. By the time a hair cell has been pushed through the entire follicle tube to the surface of the head, it is dead. Hair is not alive, which is why it does not hurt to cut it! The more cells that are added, the longer the hair grows.

In case you are wondering…Hair grows about 1 cm every month.

Hair does not keep growing and growing forever. Every two to seven years the follicle stops adding keratin cells. The hair stays attached for a few months and then it falls out. Every day,

50 to 100 hairs fall out of a person’s head. New ones start to grow in their place.

Hair color of all shades are the result of the presence of one chemical, melanin, which is transferred to hair cells inside the follicle. Melanin is also found in skin. Dark skin has more melanin than pale skin. When people get a tan, their skin cells are producing extra melanin. Similarly, the darker the hair, the more melanin its cells contain. Black hair has the most melanin, red hair has less melanin, and blond hair has less still. Gray hair has even less melanin, and pure white hair, like Santa’s, has none.

As people get older, especially when they have lived for fifty years or more, the color cells start to disappear, and there is less melanin to transfer to the growing hairs. We are not sure why these cells disappear. For some people it happens slowly over many years. For other people it happens quickly. Hairs still keep growing, they just don’t have much color in them any more.

Santa's white hair tells us a lot about him. It is a sure sign that Santa is probably well over 50. (It is unusual, but occasionally a young person has no melanin in their hair.) As well as being white, Santa’s hair is thick and shiny. This tells us that Santa is healthy and eats plenty of good food. Also, when a person goes out in the sun a lot, their white hair gets stained yellow. Santa’s bright white hair tells us that he does not spend a lot of time on the beach. Christmas keeps him much too busy for that!