Do Heat and Time Really Make Deep Conditioning More Effective?

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From The Natural Haven Bloom‘s series on Deep Conditioning

For the past couple of weeks we have been talking deep conditioning. Today is the turn of two factors that are really key namely temperature (should you use heat when conditioning?)  and time (should you leave a conditioner on for hours?).

Now for the purpose of this post, I will again define a conditioner as a water based conditioner (deep, intensive, mask or rinse out). If you are using oil, this is completely different and its own rules apply.

So will heat and time affect conditioning? The quick answer

Increased time and temperature do increase the amount of conditioner adsorbed to the surface of hair. The maximum time is 20-30 minutes and the maximum temperature is around 35°C.

The long answer

I am being very general in this post because the fact is that every single ingredient that can adsorb and/or penetrate into hair (e.g surfactant or protein) actually has its own unique behaviour when added to a conditioner. This is also affected by other ingredients in the conditioner.  However there are common similarities in behaviour and these are the ones I wish to emphasise.

1.  Increasing the time you leave conditioner on hair allows more of it to adsorb with a maximum adsorption at 20- 30 minutes.

The key ingredients that can stick to hair (surfactants, hydrolysed protein, silicones, polyquats etc) will do so within seconds of applying the conditioner. If left on hair for longer, the amount will in general double within 10 minutes. If left on for another 10-20 minutes, the amount will increase by another 60-100% of the mark set at 10 minutes.

However after 30 minutes from initial application, there are no more increases in conditioner adsorbing to hair. The reason for this is that the hair conditioner simply has no more places on the hair where it can stick to…….all gaps which it can plug and all surfaces where it can attach are occupied.

The general graph that is obtained looks something like this

The relationship between conditioning time and adsorption

 
If you look at the 10 minute mark, you can see about 5% is on hair and at the 30 minute mark this increases to 10%. However at 40, 50 or 60 minutes there is no further increase, it just stays at 10%. Please do note that the numbers  5% and 10% are NOT real measurements. Adsorption is usually much lower than this (even as low as 0.01%) but for ease of digesting the information I picked simpler numbers like 5 and 10.

2. Increasing the temperature of a conditioner to surface body temperature (around 35°C) increases adsorption of a conditioner 

Temperature increases the adsorption of conditioner such that slightly more can stick to the surface.  Generally tests are not performed much higher than 35-40°C in order to not burn the skin.  The graph looks something like this

There are two main lines in the graph one in blue at 20°C and another in orange at 35°C. What you see is that the orange line is shifted just slightly about the blue one. This means when conditioner is heated to 35°C, at 10 minutes there is slightly more than 5% on hair and at 30 minutes there is slightly more than 10%. Therefore temperature increases adsorption. The rule however remains the same in terms of no further conditioner sticking to the surface after 30  minutes.

 
Other influencing factors

1.  pH : The pH of your conditioner matters. In general pH between 6-7 work well to increase adsorption to hair. Below and above this range, the behaviour of the conditioner can become a little more erratic
2. Ingredient Quantities: Conditioners are different and contain different quantities of ingredients. For example, a conditioner which contains 0.2% hydrolysed protein will be able to leave about 20% more protein on the surface of hair compared to one which has 0.1%.  The result is more dramatic for surfactants with a 0.2% conditioner able to adsorb 80% more to the surface than a conditioner with 0.1% surfactant. The thing is, manufacturers will not tell you how much is on the jar, so you have to try the product and trust that your hair will tell you whether the product has too much or too little of the ingredient you are looking for.

References 

J Soc Cosmet Chem, pp 259-273, 1992
J Soc Cosmet Chem, pp 351-359, 1991
J Soc Cosmet Chem, pp135-152, 1969

I will put up a summary post next week in combination with your key questions from the series. This is probably one of the more complex posts that I have put up so if you do not understand anything here, feel free to shout!

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The Natural Haven

The Natural Haven

Scientist on a hairy mission!

 

31 thoughts on “Do Heat and Time Really Make Deep Conditioning More Effective?

  1. I love this article because I am kind of a nerd, and I love the science of things. ;)

    I have heard of naturals doing 8 hour conditioning treatments so it’s good to find out that 30 minutes is really the maximum absorption time. When I deep condition, I typically sit under a hair dryer for 15-20 minutes with good results.

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  2. Very good blog post. I haven’t been following the deep conditioning series, but after reading several of JC’s posts as well as that of another cosmetic scientist in the natural hair community, I’ve made sure to only leave on deep conditioners as long as the container says. I also don’t add heat unless it says so. Following the directions is key to achieving optimal hair health. Thank you for this post!

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  3. Basically, it seems as though the effectiveness of a deep conditioner is based on the actual properties of the conditioner and how long it is left on the hair until saturation point is reached. Heat facilitates the adsorption, but once saturation point is reached (30 min), no other benefit is had by heat.

    Some ingredients are ADsorbed (attach to the surface of the cuticle) more readily than others. Products with pH in the same range as hair itself, being the most easily ADsorbed. Very few ingredients are actually ABsorbed (taken into the cuticle). Moisturizing oils like jojoba, coconut and argan oils closely resemble the structure of sebum (the body’s own naturally made oil) and are the most effective moisturizers.

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    • lol I am so going to adapt your way of writing aDsorb. It is a really important concept that I covered in the first part of the series on my blog.

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  4. Yes. I know what the science says, but when I’m feeling out of it and not in the mood to do my hair, I’ll throw in some conditioner and keep it in a bun for one or two days. and when I take my hair down and rinse the conditioner out, it feels aMAAAAAAAAAAAAAZINGLY soft! Softer than it does when I just have it in for 1/2 hour.

    There is something to this…I think science just hasn’t figured it out yet.

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    • Actually the series is not finished. I will give you a heads up, the reason why you hair feels so soft is pretty much the same way your nails get softer when you soak them in water for a long time. It is related to the keratin conformation (keratin being the protein in hair and nails).

      For nails the truth is the more often you soak them, the weaker they eventually become (have you ever tried washing dishes by hand everyday for a week and compare how your nails feel compared to a week of not doing that?)

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      • I was going to say something like that, but without the science:). I’ve also learned about the downfall of over-conditioned/moisturized hair. I do tend to leave my pre-poo (Vatika oil mixed with Aubrey GPB, Honeysuckle Rose or both) in overnight for the coconut oil benefits and because the study behind that was with an overnight treatment. But, I only leave DCs on overnight anymore out of pure exhaustion and/or laziness as I know that too much of a good thing can become a bad one. I’ve learned that extra soft hair actually isn’t good and a little “body” is an indicator of strength and elasticity. I had a lot of breakage when my hair become too soft and it snagged in everything. My hair is so much stronger now that I’ve incorporated protein and reduced my moisturizing DC times to no more than an hour (I’d do a half hour, but the time always escapes me before I know it. So, as long as the hour doesn’t seem to do any damage, that’s how long I typically leave a DC in, although it might not result in any increased benefit over a half hour).

        Shelli

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  5. you know what? All I can tell you is how it works for me. In my experience? YES, they absolutely make a difference. Having the conditioner on for like 5 minutes wouldn’t do anything that drastic to my hair, so the next time a scientist says it makes no difference, he better show me a demonstration on his OWN hair while trying to tell me its making no difference, lol.

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    • I have already done a post on why hair care needs to be tailored to your personal experience. Science can only give you insight into what is happening at a molecular level.

      By the way, I am a female scientist. I do wonder why certain professions are almost by default classed by male gender ( doctor, scientist, pilot).

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  6. Does it also depend on how porous your hair is? I have high porosity hair, so I’m sure five minutes is enough for me. But for low porosity naturals, maybe the extra hours are beneficial?

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  7. Tbh, I leave conditioners in longer usually due to laziness. 30 minutes is too long to stay in a ‘wet’ state (e.g. in the shower) and if I’ve come out of the shower, dried and dressed myself (or put on PJs), I am loathed to wet my head again. Also, nightly deep conditioning would mean rinsing it off and going to bed with wet hair. DC’ing overnight and rinsing out in my morning shower works well for me! It then has all day (and another night if needed) to dry and stretch.

    Two additional points are that my hair is not at all porous, is thick and is coarse, so the softening process (which is usually what I want from a DC since I clearly have enough protein in my hair already) takes added time to penetrate my strands AND the thickness of my bush (especially if the conditioner is itself thick and not easily spread into hair).
    Additionally, my hair does not liked to be rinsed upside down, so that bending over the sink/tub with showerhead life is not for me. Lol!

    One FINAL point is [due to laziness again] I like to DC to soften and remove shed hair prior to washing, so again overnight DC’ing, morning washing is best. The softness lasts even beyond washing, shed hairs are out of the picture by the time it’s wet and my hair doesn’t feel stripped. WIN!

    Urgh! How did one quick point evolve into an essay?! (O_o)

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    • +1 I’m an overnight girl, at least until I figure out how to do a WNG at night. Napptural85′s winter wash and go only worked on 10% of my hair, the rest was an undefined mess.

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  8. I also think it depends on your hair if I leave conditioner in for too long my hair becomes limp and lifeless and really quite nasty. I find that 30 minutes with a hot towel or in the steam room is quite enough. However if I am in the sauna my hair can take longer periods say an hour. I’m sure someone knows the chemistry behind this.

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    • You are totally right, the truth is many naturals actually LIKE the feeling of overconditioned hair (extremely soft, tends to hang a little/ be limp/ not hold a curl).

      More often people who have hair that can form ringlets/spirals will tend not to like overconditioned hair as it prevents the curls formation and makes hair feel mushy. If you are in this group, you may find that as little as a quick comb through with the conditioner is enough for you.

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    • Right, it is possible to over-condition. I had that mushy feeling because of overconditioning. Now I have cut back on the frequency of conditioning and I also make sure to also use a protein product.
      Everything in balance!

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  9. I think body heat is enough to make the treatment be absorbed, I do this with some pro naturals argan oil and a shower cap and my hair looks super shiny and smooth afterwards.

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    • Body heat, which certainly is enhanced by using a plastic cap, isa heat source, but the scales of the outer layer may not open as much for maximum product uptake. Still it does help, and I have done it many times. However, being a woman with extremely dry and brittle hair, I like maximum effect!

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  10. At the end of the day just like products and styles, it comes down to personal preference. The amount of time we keep in conditioner is based on the “feel” we want. Personally, when im gonna do curls i go for an hour, other than that, its just the specified 5-10 mins

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  11. The heat causes the scales on the outer layer of the shaft to open. That allows the product to penetrate the shaft, not just stick to the outer layer. The product has a better effect if it penetrates the shaft.

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  12. Wow this is so interesting. I’ll think about decreasing my deep conditioning time, but I need to do more research first. Here is my favorite deep conditioner.

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  13. I’m not sure if you have heard of a woman named Talisha Berry, but I had a pleasure of meeting her while at a conference for work in Portland. Talisha shared her book tips with me and also allowed me to sample her new hair growth product which includes a blend of organic essential oils. I lie to to you not, my hair has grown 4 inches and is so healthy and that was just 3 months ago! My hair is coarse and very thick and I was suffering from breakage. I would definitely recommend you ladies to check her out. She promotes hair tips and secrets on natural and relaxed hair. Her YouTube channel is: http://www.youtube.com/talishassecret and her website is TalishasSecret.com
    ~Vanessa :)

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  14. I disagree. Time and consistent humidity make a difference in conditioning the hair. When I condition my hair overnight it turns out alot shinier and feels softer than leaving on a conditioner for 30 minutes hence minimizing breakage. The hype is real. I also say humidity plays a major part because when I went under a steamer versus a dryer with a conditioning cap my hair was alot softer again and shinier.

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    • Heat causes the scales on the hair to raise up, which then allows your product to penetrate the hair shaft better, and give the intended results. I do use products without external heat in a pinch however. A plastic cap for 10-30 minutes is better tnan nothing.

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  15. I love this post I’ve always wondered if keeping deep conditioner on for hours is actually worth it especially when it starts to drip like mad.

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