Hair Swelling in Water

This subject came up recently on the Wavy Hair Community and I wanted to do a little research to find out how much water is too much - and for how long.

©Science-y Hair Blog 2013

Hair does not take on water immediately, it is designed to repel water in it's unaltered state. Whenever I put hairs in water to photograph them, they do not swell dramatically to the point at which the cuticles are standing up and things look awful. The measurements you'll read about below are tiny. Your hair is probably more protected than the hair cited below by things like conditioner, hair gel and maybe oils - including those that protect your hair naturally. There are 2 ways to get hair to swell with water - expose it to high relative humidity and soak it in water.

When hair begins to swell with water, the swelling is initially distributed along the length of the hair and hair can actually increase in length (temporarily) as a result. But not very much. Think of the pressure exerted on a garden hose when the end is open and water is flowing freely.

When hair is maximally swollen, the pressure of the water strains against the perimeter of the hair shaft. Imagine garden hose in which the "open" end has been plugged. Swelling creates an increase in diameter.

Hair takes on water in high humidity, this causes swelling. At 40% relative humidity, hair can increase in diameter by 5%. At 60% relative humidity swelling can be 7%. When the relative humidity is 100%, hair can increase in diameter by almost 14% because it has taken on water from the air around it.

Things which dramatically increase swelling of hair (much more than water alone): sodium lauryl sulfate, thioglycolic acid (perms), other detergents when concentrated, high pH solutions. Glycerin actually causes less swelling than water!

©Science-y Hair Blog 2013

Swollen hair has several problems. One is that swelling increases pressure and pressure tends to strain tissues. Strain after strain weakens hair over time. Swollen hair's increased girth means that the cuticles stand out - as though you glued tiny shingles on a balloon and then blew it up. That allows water into areas which should be protected by the cuticle. Swollen hair gains weight as well as girth. This causes it to either express its curliest version of itself if the curl is strong (then the curls lose definition to poufy frizz), or go limp when curls are present but not strong relative to the weight of the fiber+water.

Swelling and loss of proteins:

The area just beneath the hair's protective cuticle layers or "endocuticle" of hair may be the area most prone to swelling. It is also loaded with water-soluble, polar -therefore water-attracting- amino acids. It is covered by the membrane-like exocuticle and the sebum from your scalp, both of which provide water and chemical resistance, but both of which are also subject to chemical and physical degradation. In other words, when you get your hair wet, you lose amino acids (protein) from your hair.

How long is too long?

One study published in the Journal of the American Academy of Dermatology tested caucasian hair, African hair and Asian hair swelling when soaking in water vs. time. By about 150 seconds all hair had reached its maximum swelling. That's less than 2.5 minutes in water! Note: The authors did not mention whether the hair had been washed prior to testing, or had any other treatments. I think it's safe to assume it was washed first.

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Heat, water and oils:

Water alone does not remove oils. Water and oil do not mix! But oils are not all the same. Oils from your scalp, oils you apply to your hair (including conditioners) can be more-or-less solid at room temperature. Many oils from your scalp and in conditioners have high melting points - coconut oil is an example. Heat can melt certain oils. If they can be melted, they are more likely to be removed with any sort of detergent (even cationic ones) and they are more likely to be carried away with water if possible. Especially if combined with a long soak in which some of the oils might find their way free of the hair. This is why warm to hot water cleans greasy stains better from laundry. 

What can you do to reduce water-damage?

• Use emollients like coconut oil or other hair-penetrating oils to help make your hair more water-repelling to slow the movement of water into the hair. Conditioners may also be helpful. Here is a post with pictures of hair protected by various oils and conditioners in chlorinated (and high pH) water).
• Use not-hot (lukewarm or cool) water for washing your hair. Your skin likes that better too.
• Keep the amount of time your hair is in the water to a minimum. By the time you've been in the water for 2 minutes, your hair has swollen as much as it can. But I think you have a little more time than that, thanks to hair gel, and conditioners which form a film on the surface of your hair.
• Wash your hair as infrequently as you can stand. The oils from your scalp are well-suited to keeping your hair healthy and hair is designed to repel water by itself if it is not damaged or over-handled.
• Reconsider bleaching and highlighting and other chemical processes. These treatments make hair more porous - so it takes on water sooner. These treatments also erode the epicuticle, leaving your hair with less natural protection. If you do these to your hair, take extra steps to avoid getting waterlogged.

I don't know about you - I may have to start leaving my hair dry until the end of the shower. And I take fairly quick showers! 

2003 Current research on ethnic hair

Journal of the American Academy of Dermatology, 48 No. 6

A. Franbourg, P. Hallegot,  F. Baltenneck, C. Toutain,and F. Leroy

Chemical and Physical Behavior of Human Hair 

Robbins, 1994. 3^rd Ed. Springer-Verlag, New York

pH and Your Hair. A little redox to make you happy.

Here's what I know and what I think about pH and hair products. This is "redox" chemistry (oxidation and reduction). One of my teachers said to our class, "Next week, we'll be doing redox," followed by an evil laugh. I love it because it applies to so many living systems we work with every day. I think you will too.

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Get ready for a chemistry smackdown on hair cuticle folklore. Forget all that stuff you've heard about cuticles being open or closed as a result of different pH. Cuticles being "open" when it is the result of a solution you put on your hair is a side effect of hair swelling in the wrong pH, in strong detergent, or in just plain old water if it's wet for too long. Likewise for cuticles being "closed."

The shortest story possible: If you do not want to suddenly damage the structure of your hair in an irreversible way - keep it out of solutions with a of pH 3 or under, and out of solutions with a pH 9 or above. Especially do not leave your hair in these solutions for a long time. For that matter - keep those sorts of solutions away from your skin and eyes also!

These extremes will tend to cause the hair to swell, take on acid or base, and structural damage is the result.

©Science-y Hair Blog 2013

Examples of things you might want to avoid putting in your hair to avoid those extremes: pH 2 is undiluted lemon juice, straight vinegar can be pH 3, so can soda drinks. Why you would put soda in your hair, I don't know. But you put it on your teeth when you drink it, which I find disturbing. To get to pH 9, you need (diluted) sodium hydroxide, lithium hydroxide, potassium hydroxide, or guanidine hydroxide used in hair relaxers or ordinary soap (the kind made from fats and lye).

If you remember one thing from this blog post:

Rinse-out products are safest for hair between pH 4 and 6.

Leave-on products are safest for hair between pH 5 and 6 (or 4.5 and 6 for bleached or lightened hair).

Treatments which use heat or are meant to be more than superficial are safest between pH 5 and 6.

To prevent sudden and irreversible damage to hair, stay between pH 4 and 9. 

©Science-y Hair Blog 2013

The slightly longer story

Keep in mind that products marketed to the entire family are assumed to have contact with eyes, nose, and mouth during use and when rinsed off. So a neutral or near-neutral pH around 7 may be ideal for safety reasons.

You also need to know that certain preservatives are more active in a specific pH range. That means that the product pH needs to be kept tightly within a specific pH range to assure the preservative will work well and continue to work for the full anticipated shelf life.

These non-hair considerations are a big deal because irritating people's eyes and noses and mouths is dangerous and potentially litigious, and choosing a preservative which will work with the variety of ingredients in a product and stay stable for 1-2 years is one of the more difficult aspects of product formulation.

©Science-y Hair Blog 2013

Electric hair

Your hair is mostly protein and oils and water (if you ground it up and measured what is in there - that's what you'd find). Those things carry charges - positive or negative. Hair tends to have a greater number of negative charges when you're running around during your day. We're dealing with the surface of the hair because that's where these solutions mostly act. Once hair has swollen in an inappropriate pH solution, you begin acting on the interior structure. Bad news! 

Brown rectangle is a hair, at right the net charge
is negative because there are more negative
charges than positive ones.

Charge is sometimes pH-dependent. If you move an item from an acid environment to an alkaline or basic environment, it will switch to an opposite charge as it gains or loses electrons to the environment. It's electrons that represent charge in the first place. 

Hair (proteins and smaller particles) have an "isoionic point." That is the pH value at which it is in balance between positive and negative charge - there is no "net charge," the same number of positive charges and negative charges exist at the surface. Your hair is taking up neither acid nor base from the solutions it is in contact with. It's stable under these conditoines. Everything is groovy.

If you put your hair in a solution lower than 5.6-6.2, such as vinegar or lemon juice or a citric acid rinse, it will take on acid (that's protons or + charges). If you put it in a solution higher than 5.6-6.2, it will take on "base" or OH- charges. That's right - when you use baking soda-water on your hair and it feels extra-soft, it's soaking up base and taking on that slippery, slimy feel shared by many bases. Shifting the electrostatic charge on your hair takes a toll because you can't do that without altering the chemistry of the proteins and oils that make up your hair in some way.

Hair at its isoionic point
between pH 5.6 and 6.2. Positive
and negative charges are in balance.

What is healthy hair's isoionic point hair? Around pH 5.6 to 6.2.

But there's more! Has your hair been oxidized by bleach (highlighting, permanent dye, swimming pools) or by the sun? In that case the isoionic point decreases because oxidation changes the chemical composition of the surface of your hair. You might be able to go a little lower in pH - and benefit from it. This is one reason why products for color-treated hair often have a lower-than-neutral pH and are marketed based on that feature.

So what!? We rinse a lot of these products off in pH ~7 water, right? Yep. Though even brief, repeated extreme pH insults would still be a bad idea. 

©Science-y Hair Blog 2013

Below pH 5, acids enter the hair if left on hair for a long time.
Hair loses its charge balance. Above pH 7 to 8, "base" enters
hair. The - and + charges above show how these charges are
added by the solution - it's a visual aid, not an absolute reflection
of the whole oxidation/reduction picture.

So why are some products formulated with a lower-than-5 pH?

Because bleached hair can go lower, and many people's hair can potentially tolerate a lower pH if they are quick about it. That's where the isoelectric point (different from "isoionic") comes into the equation. Your hair's isoelectric point is way down between pH 3.4 and 4.5. Isoelectric means the hair temporarily has zero charge. If you read about these things online or in the popular media, you will encounter the idea that a quite-low pH product, having knocked the charges away, leaves your hair with tightly-closed cuticles and therefore very resistant. That is not an adequate explanation for me!  I prefer to think of it as the point at which your hair is "non-reactive." Non-reactive refers to what happens between hair and things you put on your hair. "Tightly closed cuticles" implies that once you close them, they cannot be opened like a locked door. Or something. It doesn't hold up to scrutiny, such as the question, "Okay, but then what will keep them closed?"

We must ask ourselves - if the hair is charge-free, how will it bond to cationic-charged conditioners for better slip? Indeed, it seems that cationic conditioners are more strongly adsorbed to hair (adhere more firmly) above pH 3.7. You need some negative charges on there, people! A lower-than-4.5 pH would be completely counter-productive in a cationic conditioning product.

Representation of conditioner bonding to hair based on the
attraction of opposite charges (left).  Pink + charges at
right represent conditioner not bonding to hair at pH
values below 4.5 when hair has a "zero" charge.

©Science-y Hair Blog 2013

The take-home message:

For short-term, superficial treatments like shampooing or conditioning or rinses the isoelectric point sets the very bottom limit: Below pH 5 your hair is out of balance, but not necessarily in danger. You're not going beneath the surface of hair with these treatments and they are short-lived. Stay above pH 4 and below pH 6 and you're in good shape. For a pH 4 or 4.5 hair product (like a gel) that will take many hours to dry in your hair - that might be a problem. It's still superficial or a surface-only treatment, but the length of time it stays wet and therefore active might cause problems. Probably better to be around pH 5.5 for that, unless you have lots of highlights or bleaching with hair dyeing.

It's those longer-lasting and more invasive treatments like permanent waves, hair bleaching, high-heated treatments in which you absolutely must keep hair in that 5.6-6.2 range, especially because it's not just the surface you're dealing with - perms and bleaching are deeper than the cuticles. Hence the "acid perm."

Why does my hair not respond well to acidic rinses?

So if low-ish pH isn't necessarily evil to your hair, then why can vinegar or citric acid rinses leave hair feeling dry and rough? Let's say your hair is porous (even if just the ends are) - those solutions with a less-friendly pH get into your hair more easily and have access to a lot of surface area. You just got a bigger dose.

Acids have corrosive action - they donate those "+" charges that lead to rusty metal. Acids can dissolve things like calcium. Acids can destroy fats and proteins. Think of what happens if you put lemon juice in milk (it curdles). Or if you put a nail in a glass of Coke. Weak acids like vinegar or citric acid can strip off some surface oils and proteins. Acids may interact with your water, with the mineral deposits on your hair, the ingredients in your products. The possibilities are endless. There's nothing wrong with an occasional vinegar or citric acid rinse as long as they're diluted properly but chemically, it can be a wild card. 
Some people have very resilient hair that can tolerate acidic rinses whereas other people's hair will swell and take on acid immediately. Some people's hair can tolerate acids but not bases. Everybody's hair is different for so many reasons.

©Science-y Hair Blog 2013

Test pH at home:

Get yourself some pH strips in the aquatic pets section of a pet store or the swimming pool section of a department store, or from your local drugstore. Make sure they measure below pH 7 as well as above. Test your homemade rinses and adjust accordingly. You can test other products also. Conditioner often gives a less-than-accurate reading because it's not all liquid (there are fats in there). But you can get a rough idea. 

What you do with this information is up to you. In my world - if I wanted to chemically relax my hair, I'd do it and hope it didn't eat the skin on my scalp. If I wanted to wash it with bar soap, I would do that (but no thank you to the soap scum). And I'd be armed with the knowledge that my hair had been chemically altered and therefore I would need to give it extra gentle care. If you want to use a citric acid or vinegar rinse - go for it. If it's too strong the first time, whip out your pH strips and find a pH your hair can tolerate.

Chemical and Physical Behavior of Human Hair 

Robbins, 1994. 3^rd Ed. Springer-Verlag, New York