Wednesday, May 12, 2010

Chemistry of your hair: Adsorbing and substantivity

Two definitions you should know when dealing with hair care products - what it means when something is substantive, and what it means when something adsorbs to your hair. (From the post "How conditioners work!" from July 25, 2009...)

A conditioning agent (like Incroquat BTMS-50) is a cationic quaternary compound. It's a positively charged compound that adsorbs to the surface of your hair. (Adsorption means the molecules accumulate on the surface of your hair. It's different from absorption in that it doesn't penetrate, it just sits on top of the hair fibre.) This is called substantivity.

Substantivity is defined as "an adsorption phenomenon by which materials that have opposing charges or like composition are more readily adsorbed onto or attracted to its surface and, once there, resistant to subsequent rinse-off." In other words, a material that is positively charged - like our cationic ingredients - will be attracted to the surface of our hair, which is negatively charged.

The cationic quaternary compound is hydrophobic - "scared of water" - so it will resist removal by water alone. (The more hydrophobic the quaternary compound, the less likely it is to be removed by water alone.) So the positively charged cationic quaternary compound is attracted to your negatively charged hair fibre and clings on to the surface.

Being resistant to rinse-off doesn't mean it won't come clean and cause build up; it just means it won't rinse off when you rinse your hair after applying the conditioner. It will rinse off when you wash your hair with shampoo in the future. If you are worried about build up of styling products, consider adding cetrimonium chloride to your products - 2% is enough! 

Cationic quaternary compounds increase the lubricity, static control, and combability (is that a word?) of your hair. It's always a good thing to have extra moisturization in your hair, increasing the water content on the hair fibre, and increasing the lubricity of our hair. By doing these things, you're reducing the force required to comb or brush your hair, which means fewer broken or torn out hairs and less static electricity on the surface!

If you are using a product that is negatively charged (anionic) or neutrally charged (non-ionic) as a conditioner, it will not offer substantivity to your hair. So something like apple cider vinegar (non-ionic, acidic) will not adsorb to your hair strands, which means it won't increase the conditioning of your hair, which means you aren't reducing the combing forces and the friction to your hair. Oils (non-ionic, neutral pH) will coat the hair strands to increase lubrication and moisturization, but they aren't substantive, so by definition they aren't conditioning. They still offer some awesome features to our products and our hair, but they aren't conditioning. 

When formulating a conditioner, we want maximum adsorption and maximum substantivity to get the most out of the product. We do this by choosing a cationic quaternary compound that will adsorb to our hair, like Incroquat BTMS or cetrimonium bromide. The cationic quaternary compound is always the basis from which we work when creating a great conditioner.

We can increase our substantivity by adding a fatty alcohol, like cetyl alcohol, to the mix. Fatty alcohols increase the substantivity of the conditioner by adsorbing to the hair fibre as well and encouraging more adsorption by the quaternary compound. And we add all the other goodies like hydrolyzed proteins, oils, butters, silicones, and so on to increase the substantivity, adsorption, and moisturization of our hair.


April said...

How does moisture make curly hair frizzy? If attracting moisture to the hair is a good thing? What is good moisture and what is bad moisture?

I have dry, curly hair. I get nothing but frizz in the humid summers unless I slick it down with oils and polymers(?)

The Caravan said...

I love your blog, I'm so happy I found it. My brain is gobbling up all the info like a maniac!

Susan Barclay-Nichols said...

Hi April...Give me a few days and I'll cover that topic! (Considering frizz is about water absorption, oils and polymers are pretty much the only things that will keep the frizzies at bay!)

Hi The Caravan. Thanks for your kind words! I hope you'll enjoy all the information coming up on hair - I find this topic so fascinating!

Anonymous said...

Really enjoying this series! Thanks for doing it! :)

- K_Angel

Julianna said...

Hmm.. my hair is very fine and frizzy. No matter how much oil, dimethocone, etc I use, it is still a frizzy mess. Any advice?

Anonymous said...

Hi! I found ur blog just yesterday but i'm falling in love! My question is... are silicones really sure and healthy for our hair? This is what i know: silicones occludes skin pores and cuticular layer of our hair, and don't let him repair from the inside... isn't real? And, also, is a petrol product, right?
Sorry for bad english -.-
Hope you'll answer me :D

Sânziene şi Mătrăgună said...

this is my bad English day :)

'Adsorption means the molecules accumulate on the surface of your hair. It's different from absorption in that it doesn't penetrate, it just sits on top of the hair fibre.This is called substantivity'

let me put it in other words :)

So, a cationic ingredient will accumulate at the surface of the hair due to the property called "adsorbtion".

If an ingredient penetrates into the hair not because it is positively charged, like cetearyl alcohol or proteins or oils, this is adding substantivity, am I correct?

Anonymous said...

Apple cider vinegar is alkaline? really, I always thought vinegar was acid

Susan Barclay-Nichols said...

Hi Anonymous. What a typo! And scary that you're the first person in almost 4 years to catch it. As a note, I will have to delete your post as you didn't attach a name. Want to revise it?

Anonymous said...

I think we might as well get used to the frizzies because i personally don't think there is currently a product that will take frizzy alway from our hair 100%. The only time i don't have some frizzy going on up there is the day i wash my hair and apply lots and lots of leave in lotion and the next day....there they are again. I embrace it and keep on applying lots and lots of lotion.

yadith urieta martinez said...

lindo tu trabajo y gracias por ofrecernos tantas cosas buenas

Anonymous said...

Hi Swift, I had no luck getting answers to my other questions for now, but I'm perseverant, so here is a new one because I can't find straight answers.
I understood that an acidic pH won't offer any susbstantivity to hair. But I also read a few times that an acidic pH will have a a slightly shrinking effect on the hair, making the scales more compact, 'closed'. Wouldn't that indirectly impact the substantivity (if that is in fact the case)?
You talk a lot about how pH is very important for our hair products, but not much about the specific effects of a more acidic/alkaline pH. Do you know if the idea that pH impacts the raising of the cuticule is more of a fact or a myth?
Thank you in advance, and again, thank you for your goldmine of a blog!

Susan Barclay-Nichols said...

Hi Laeititia. Where did you get the idea that acidic ingredients aren't substantive? All the ingredients we use should be acidic because our hair responds better to acidic ingredients over alkaline ones. Are you perhaps mixing up anionic over cationic or negatively charged over positively charged?

I have written about pH in this post on why cold process soap doesn't make a good shampoo.

If you aren't getting answers to your questions, it could be that I've been really busy or ill or it could be that your question has been answered elsewhere in the blog. I do what I can. I write this blog in my free time and there's only so much I can do in one day...

Asha said...

Hi Susan, You mentioned in the post the add cetrimonuim chloride if you are worried about the build up. Could you please let me know how does it help and what is the relationship between the two. Thanks!

Tole Shuma said...

Hey Susan being in Africa most of my clients hair get dry(Am a stylist/Cosmetic chemist)
i go t interested in creating lotions and decided to do a hair moisturizing lotion without putting a cationic ingredient...I didn't like how the product felt on the hair.Ive tweaked one and decided to put cetrimonium chloride at 1%,As I post this comment haven't used it yet on my clients but my hunch tells me it will work,thanks to this Goldmine of a blog.
Now i understand the whole hair adsorption,lubricity,anionic jargon ..I feel like areal scientist...

Kim said...

What do you think of Formulator's Sample Shop Cationic Glycoprotein and Formulator's Sample Shop Lycopene BioFerment as replacements for traditional quats? I have contacted the supplier and they claim that "they provide the same condiitoning with the use of quats." Forgive me for my ignorance, but why can only cationic ingredients condition the hair? Will any acidic ingredient condition the hair? Can this conditioning plant emulsifier condition the hair the way BTMS would? Also, the aforementioned plant-based conditioning emulsifier (not BTMS) has a surfactant. Do surfactants wash away the conditioning properties of conditioning emulsifiers like the one I linked to?

Kim said...

Also, how can one determine whether an ingredient is substantive to the skin/it won't rinse off after washing? In some posts, you say that chamomile extract won't rinse off. How do you determine if an ingredient will rinse off after washing?

Susan Barclay-Nichols said...

HI Kim. As for the first comment, I have used the lycopene bioferment - there's a post around here about that - and I really like it. As for the glycoprotein, I haven't used it, but if it is positively charged, it will be conditioning.

Cationic ingredients condition the hair by being substantive. It isn't about being acidic or basic, it's about the charge of the ingredient, although we want our hair care products to be acidic as that is the pH of our hair. I encourage you to visit the hair care section and checking out the post on that topic because it sounds like you want to know more about this!

I'm sorry, I know very little french, so I don't understand much of what is written there, but I don't see a positively charged ingredient. If there isn't a positively charged ingredient, it isn't conditioning in the sense of being substantive to your hair or skin.

All emulsifiers are surfactants, meaning they reduce the tension in the interface between oil and water, so things like behentrimonium methosulfate and Polawax would be considered surfactants, too. (There is a post on this topic in the surfactants section.) No, surfactants don't necessarily wash off the conditioning properties. In fact, the substantivity of the positively charged ingredient is why we can make 2-in-1 products that wash and condition at the same time. (Again, check out the post on substantivity as I think it'll answer your questions!)

As to your second comment, you have to ask your supplier or read more about the ingredient. There isn't a way to know which non-cationic ingredients will wash off and which ones won't. For instance, sodium lactate will, glycerin won't. Positively charged ingredients, in general, will not rinse off easily.

Anonymous said...