Thursday, 4 March 2010

Moisture Issue: Glycerin -the science bit

The first post on glycerin was getting a little bit too long so I decided to split it up. Please see the first post here which details the moisturising effect of glycerin.

This post is about the science. The way glycerin works is not fully agreed upon. The two arguments placed forward are

1. Glycerin penetrates hair - 'Glycerin is known to penetrate the fiber and is unlikely to localize moisture in the vicinity of the surface. '(J Soc Cosmet Chem, pg 39-52, 1985)

2. Glycerin doesn't penetrate hair (to be completely scientific, they are talking about glycerol which is pure glycerin without any water. Dewetting the surface means the glycerol holds onto the water present on the surface) - 'Glycerol is known not to penetrate the hair and it probably quickly dewets the outer surface of the scales.'(Journal of Colloid and Interface Science,pg 329–335, 2004)

In the diagram below, I decided to show how the additional water comes in. In the event that you mix glycerin with water, the relevant images are the last two on the right.



In my opinion, glycerin is quite small and likes water. Hair easily lets water through and as we all know, coconut oil too. Therefore I think glycerin does penetrate hair to some extent. What do you think?

13 comments:

  1. I think I'm confused. I love your posts and the science behind our haircare but this glycerin thing has my brain whirling around in my skull. Thank you for the info but I think I'm going to have to re-read this in the morning after a good nights sleep. Rest assured, you did a terrific job. I'm just having one of those days.

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  2. I think maybe it doesn't b/c product heavy with glycerin in them leave a weird sticky, film on my hair (or maybe it's a different ingredient creating this effect? who knows). I agree more with theory 2 and think maybe it doesn't penentrate hair but since it attracts water from the air, maybe some of the extra water it attracts goes into your hair strand? I dunno. Lol. Thanks for breaking it down some more for us.

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  3. No worries Nacala - This part was confusing for me too because of the two theories. If you are still not sure, please ask any questions that may help clarify for you.

    Great theory explanation Milan. I seriously don't know on this one. There is a pretty influential journal known as PNAS which has published a paper showing glycerin in the upper skin layers. There is no data on hair though so we can only theorise!

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  4. JC this question is on glycerin, but not on this particular series, its regarding an older post you did on glycerin (the one on KY Jelly). In that post you said the added moisture from glycerin use "prevents premature failure of hair - and therefore, premature breakage of hair when the hair is under stress (combing/stretching/pulling). However if your hair is relaxed, there is no such benefit". My question is why would glycerin not be useful in "preventing premature failure" of relaxed hair, is it already too "failed" for lack of a better term? Love your blog by the way, I feel a little like a spy since I'm relaxed but I've learned so much, I just can't stay away. :)

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  5. lol @spy. Everyone is welcome, relaxed or natural. I will have to reread the paper so I can get their explanation of why it doesn't benefit relaxed hair. I'm being thoroughly lazy for the weekend, but I will definitely answer your question soon!

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  6. So far glycerin hasnt done me any harm. I use it in my spray bottle mix with plenty of water, and a mixture of essential oils. It keeps my hair feeling soft and moisturised. But I guess everyone's hair is different

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  7. @MrsT - Yes the paper explains it exactly as you have described it. The relaxed hair has already 'failed' and the protective structure that untreated hair contains is no longer present and cannot be reinforced. Great questions!

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  8. Thanks for the the glycerin posts. I completely understand now how it works! Thanks!

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  9. Thanks for answering my question, as always your info is so informative and useful!

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  10. I've heard many naturals say that using glycerin in the winter/drier months can have the opposite affect on you hair. Meaning it will draw moisture from your hair versus drawing moisture from the air. Is there any truth in this?

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  11. DJ - In the first post which is linked at the top of this one, I detailed why glycerin is moisturising. I have also been asked the same question and I cannot explain the observation because glycerin mixed properly with water to saturation is highly unlikely to abandon the water it has to start drawing moisture from the hair.

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  12. Hi great blog! What do you think about the theory glycerin is bad for hair because it is to alkaline, and actually is damaging to hair shaft? thanks -- and happy new year:)

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  13. Sahanga - No this is not correct. Glycerin tends to have a neutral (ish ) pH (around the 7 mark). Glycerin comes from soap production, the sodium hydroxide used there is alkaline.

    I was going to pH test my glycerin but I have misplaced my strips. I will have to find them and test it. I did check material safety data sheets from commercial producers and they do say it is neutral.

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