This question was posted in our cosmetic forum. The answer took many more words than the forum would allow so I post it here.
Hi. I’m looking for recommendations where to read about the basic difference between different type of hair conditioning agents (how they work, their structural differences) and how they suit for different hair types. Are CTAC or BTAC better for fine hair or are dimethylamines/methosulfates etc. better? I’ve tried to search from books and articles but haven’t yet found any that answers my questions. My hair type (straight Asian) basically works with anything but my friend’s fine, slightly curly is very tricky and I’d like to understand better the conditioning needs of different hair types.
The most comprehensive book about hair structure and chemistry was written by Robbins and called “Chemical and Physical Behavior of Human Hair.” In this book you will learn about the structure of hair, its chemical composition, the physics involved in styling and the chemistry of how relaxers, bleach, shampoos, conditioners and color affect hair. They do cover the different types of conditioning agents however, they don’t get into the details of which one works better than another.
The main reason is likely that the book is primarily about hair and not about conditioners. However, another reason is because not everyone would agree on the definition of what “better” means. In fact, not everyone would even agree on the definition of hair types. I see the term “porous hair” thrown around a lot and the concept is not even mentioned in the Robbins’ book.
But let’s start from the beginning.
Types of hair conditioning ingredients
In a book I co-edited called Conditioning Agents for Hair and Skin we have authors cover all the major types of conditioning agents. These include
- Quaternized surfactants
- Quaternized polymers
Why are conditioners used?
To understand how conditioning ingredients work, you have to first understand why are these ingredients used? What problems are they attempting to solve? Hair conditioners have a few functions but the main ones are…
- Making hair easier to comb
- Making hair feel better
- Protecting hair from future damage
- Making hair look better
How do conditioning ingredients work?
There are really only 2 ways in which conditioning ingredients work. One way is by creating a film on the hair fiber surface. This makes the hair feel smoother when touched, reflects light better, and allows a comb to slide passed more easily. The other way a conditioning ingredient might work is by penetrating the hair fiber. This helps make the fiber more flexible which can improve manageability and reduce the chance of the fiber breaking. Some ingredients have the additional effect of attracting water to themselves which can further improve the flexibility and feel of the hair.
Conditioning ingredients like Lipids, Silicones, Cationic Surfactants, and Cationic Polymers are all about depositing a water resistant film. Humectants are more about penetrating and attracting water to the fiber.
For a conditioning agent to work, it has to be left behind on the hair! Conditioning agents that wash down your drain are not doing anything useful for your hair.
How do conditioning ingredients stay on hair?
There are a few ways you can get an ingredient to stay in your hair.
Use a leave-on product – The easiest and most efficient way to get a conditioning agent to stay on your hair is to just spray or rub it on. This is how leave-in conditioner or hair mousses work. The downside of these products is that you may not get an even distribution of product. There may be fibers or patches here and there that you miss. Plus many people don’t like the extra step of having to spray something extra in their hair.
The most popular types of products in hair are rinse-offs including shampoos and conditioners. Of these, hair conditioners are much more effective in delivering conditioning ingredients. There are 3 main mechanisms by which conditioning agents stay on hair.
- Hydrophobic Adsorption – Ingredients that are not soluble in water separate from the system during use and deposit on the hair fiber rather than being rinsed away. These include materials such as Silicones, Lipids and Emollients.
- Electronegative Adsorption – These ingredients are more compatible with water however, they have a positive charge which is attracted to negative charges on the hair fiber. Damaged protein often has a positive charge. This adsorption allows cationic surfactants and cationic polymers to stay behind on the hair and resist rinse off. It should be noted that cationic polymers can also follow the hydrophobic adsorption mechanism.
- Diffusion Absorption – These ingredients absorb into the hair fiber where they are shielded from the rinse water and will stay on the hair. Most materials will absorb into the hair a bit but the time required is so long that the other mechanisms described above are more important. However, for water soluble ingredients like humectants and proteins, this is the main way that they stay behind on hair.
While conditioners are designed to effectively deliver hair conditioning ingredients to hair, shampoos are mainly used to remove things from hair. This causes a problem for conditioning shampoos because they need to do the conflicting task of removing something while depositing something else.
So, most conditioning ingredients that rely on hydrophobic mechanism to stay behind won’t work because shampoos are made to remove hydrophobic materials. This is why putting oils in shampoos makes little sense.
This problem is further impacted by the fact that cationic materials are not compatible with the most common detergents in shampoos, anionic surfactants. So, cationic surfactants can’t be used either.
That leaves us with the diffusion mechanism which works to a small extent except most materials absorb too slowly to actually be left behind to any large extent from a shampoo.
2 in 1 shampoos
But some ingredients can last on hair even through shampooing. This include Dimethicone if it is suspended in the right way and Cationic polymers which will still follow a dilution-deposition mechanism as the shampoo gets more dilute on the hair. These are inefficient products and while a conditioning shampoo may be better than a standard shampoo in terms of leaving conditioning ingredients behind, they don’t work nearly as well as a post-shampoo conditioner.
An important thing to understand as related to the initial question is that the type of hair you have has no impact on the way these conditioning agents work.
Why do some conditioners seem to work differently on different hair?
How well a conditioner works on hair depends on a couple of factors. This includes how damaged the hair is and how easily it absorbs ingredients. But also depends on how a person feels.
If we consider conditioners work better if they reduce the force needed to comb, improve shine, and make hair feel better, then the following are true.
1. Damaged sites: Hair that is more damaged will have more places on it for where the cationic materials can bind. This type of hair may benefit from products that have a high level of cationic surfactants. Typically, longer chain (behenyl) conditioning ingredients will work better than shorter chains (cetyl) however, this can be evened out by using a higher level of a shorter chain ingredient.
2. Penetration: More damaged hair may also benefit from humectants and penetrating oils since this type of hair is more permeable and there is a greater opportunity for the ingredients to soak into the hair.
3. Less damaged hair may benefit more from ingredients that don’t bind to hair at damaged sites like oils and silicones. Of course, even damaged hair will benefit from these types of ingredients.
Wavy hair problems
Wavy or curled hair has added challenges. For example, its shape will be more prone to tangling. Its cuticle may lift up more at the turns. And it may not reflecting light in a manner conducive to shine. So, this hair typically needs more conditioning ingredients to be left behind. But leaving too much behind on hair can make it weighed down and look drab or feel greasy.
This is the main reason why any old conditioner works on your hair while your friend’s curly/wavy hair responds differently.
One last point is that how a person’s hair looks and feels is also a result of how they feel at the time they are evaluating the results. In the lab we may be able to demonstrate that conditioned wavy hair takes less combing force than unconditioned hair, but the consumer experience might not reflect the lab measured result.
A variety of things affect consumer perception including fragrance, aesthetics of the formula, and even how they are feeling about life at the specific moment. And since everyone likes different fragrances and feels different at any moment, there is little a cosmetic formulator can do about this.
What ingredients are better?
Hopefully, after reading this you’ll understand that there is no simple answer to this question. Behenyl based ingredients may provide more slip than Cetyl ingredients in a laboratory setting. But then they may feel like they weigh down the hair more so the user doesn’t like it as much. This is the same for things like dimethicone or cationic polymers.
The only way to figure out what ingredient works for anyone’s specific hair is to try products out. See which ones you feel work best for you and go with it. If you become dissatisfied try something else. There is no magic bullet.