Is hydration destroying your hair? The REAL science — Transcript

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1. 0:00should you hydrate your hair?
2. 0:01from all of the hydrating products out there  you'd think the answer is obviously yes
3. 0:06but is it all a lie?
4. 0:08there's quite a lot of hair experts including
5. 0:09scientists who say that water is  bad for your hair it causes damage
6. 0:13but that's not really true either
7. 0:15water and hydration is one of  the most confusing topics in
8. 0:18hair science it's one of the biggest  sources of hair myths not just from
9. 0:21marketing and regular people but also  hair experts and cosmetic scientists
10. 0:25but once you understand it better  a lot of things about your hair
11. 0:28and how to take care of it will  start to make a lot more sense
12. 0:32I've been avoiding this topic because  it's really complicated and I didn't
13. 0:35feel like I could explain it properly  even with a chemistry PhD even with a
14. 0:39cosmetic chemistry diploma even after  bleaching the crap out of my hair
15. 0:43but we are finally doing it here is  the real science behind hair and water
16. 0:52have you ever noticed that when  your hair is wet it's stretchier?
17. 0:55if you have long hair it's  probably pretty obvious if
18. 0:57you don't ask a friend for  a few pieces to play with
19. 1:01dry hair is stiffer if you stretch it  too much it breaks it doesn't spring back
20. 1:05wet hair is bendier it's easier to stretch  but if it stretches it will spring back
21. 1:10that's because the inside of your hair  is really sensitive to water your hair
22. 1:14is made of proteins and all of this  protein is stuck together with bonds
23. 1:19bonds give your hair its strength and  its shape there are permanent bonds
24. 1:23that only really break with chemical  treatments but there are also lots of
25. 1:26temporary bonds mostly hydrogen bonds  water is really good at breaking these
26. 1:32when your hair is dry these temporary  bonds are sticking proteins to each
27. 1:34other like glue they are holding hands at  a molecular level but proteins can also
28. 1:39hold hands with water so if you dump  a whole bunch of water into your hair
29. 1:44the proteins will start bonding with the  water instead of bonding with each other
30. 1:48it's like you and your dog are at a dog park  yes the puppies are coming back if it's just
31. 1:52the two of you you can only really interact slash  bond with each other he'll come when you call
32. 1:57but if you add a whole bunch of water it's  like you're adding a whole bunch of really
33. 2:00friendly puppies you interact with them  you're not going to have as strong of an
34. 2:04interaction with your dog you have a  temporarily weaker bond when the dogs
35. 2:08leave you have more interactions with each  other again you are more strongly bonded
36. 2:13so wet hair has less bonds holding the proteins
37. 2:15together it's a lot weaker which is  why it's so much easier to stretch
38. 2:20this is mostly why hair scientists say water  is bad for your hair it takes less force to
39. 2:24break wet hair so if you pull on it a lot more  strands will snap compared to if it was dry
40. 2:29it's like arm wrestling you're going  to win way more arm wrestles if you
41. 2:32challenge people right after they just did arm day
42. 2:36but this isn't the only thing that water  does to hair less bonds also means that the
43. 2:40shape of curly or kinky hair gets looser the  shape is floppier there are less tight bends
44. 2:46and just changing shape makes  a massive difference it's more
45. 2:49damaging to comb straight hair when  it's wet it's weaker and there's also
46. 2:52more friction from water but it's more  damaging to comb curly hair when it's dry
47. 2:57when the shape is looser there's less  resistance it's less prone to tangling
48. 3:00there's a bunch of studies  showing this weird conundrum
49. 3:03if your hair is in between straight and curly  and you're not sure if you should be combing
50. 3:07it wet or dry the science here pretty  much just lines up with your personal
51. 3:11experience the one that needs less force the  one that's easier is going to be less damaging
52. 3:16wet or dry conditioning your hair will also  make it smoother less force less damage
53. 3:20but personal experience is way more  misleading when it comes to other things
54. 3:24that water does which is where we get into  this whole idea of hydrating hair products
55. 3:30if you go to the store you'll see tons  of products that say hydration hydrating
56. 3:34so you'd think it's really  obvious more water in your
57. 3:37hair makes your hair feel nice soft smooth healthy
58. 3:41and this is one of the weirdest things  that the whole hair care industry has
59. 3:45kind of just agreed to do I've been in hair  lectures where scientists have said it's
60. 3:50too hard to explain hydration properly  to consumers people won't believe you
61. 3:53they'll get confused and they'll  just buy someone else's products
62. 3:57so I'm going to try to do the  opposite I like making life
63. 4:00harder for myself obviously but  I think you can handle the truth
64. 4:04truth handler, you
65. 4:06there is a sweet spot when it comes  to how hydrated your hair should be
66. 4:10it's actually not that much different  from skin when your skin is too wet
67. 4:14if you've been sitting in the bath for  ages it gets fragile and might crumble
68. 4:18easily but on the flip side if it's  too dry then it's stiff and it cracks
69. 4:22but there are two big differences number one
70. 4:25it's a lot harder to adjust the  level in hair with just products
71. 4:29and number two the sweet spot for hydration  with hair is a lot lower than it is for skin
72. 4:34here's the thing in studies hair that feels nice  and soft and smooth and healthy and what we would
73. 4:40think of as hydrated it actually has less water  than hair that feels rough and dry and damaged
74. 4:47there's a famous study where  scientists asked people to rate
75. 4:50hair with more water and less water and  most people said that the one with less
76. 4:54water it felt more moisturized it felt  smoother less tangled and less damaged
77. 4:59so why does hair with less water  feel nicer but then your hair
78. 5:03feels nicer when you wash it and when  you use so-called hydrating products?
79. 5:07let's start with the first bit why hair with more
80. 5:10water feels worse and again  we're going back to bonds
81. 5:13when you have extra water/puppies in the hair it  starts swelling up and different parts of your
82. 5:18hair will swell up different amounts it's like  the puppies like hanging out in particular bits
83. 5:22if we zoom into to the cuticle scales on the  surface of your hair those are those overlapping
84. 5:26roof tiles the underneath of each scale and the  glue in between the scales will absorb water a
85. 5:32lot more than the top so the scales stick up a  lot more the surface feels bumpier and rougher
86. 5:37water itself is also sticky if you  have one of those grocery bags and
87. 5:40you can't open it you can wet your fingers  a little bit not too much and get more grip
88. 5:45so when the hair has more water in it  (and on it) the surface gets bumpier
89. 5:48and grippier on a microscopic level  and to us that makes it feel like
90. 5:52it's dry because most things don't  go rough and bumpy when they're wet
91. 5:56with skin for example moisturizing  makes it softer and smoother
92. 5:59so what most hydrating hair products are actually  doing is conditioning they are depositing an
93. 6:05oily layer on the surface and this is made of  ingredients like silicones or fatty alcohols
94. 6:10this makes your hair feel smoother and it protects
95. 6:12it it makes it less sticky less of that  friction makes it feel soft and smooth
96. 6:16our hair actually starts off with a natural  conditioning layer it's called the F layer
97. 6:21it's sort of like a really thin oily layer that  sits on top of each cuticle scale as your hair
98. 6:25gets damaged this layer comes off and a  large part of what conditioners are doing
99. 6:30is they're essentially replacing that F layer
100. 6:32now here's where it gets misinterpreted  slightly by people who do know a bit about
101. 6:36hair science you might have  seen people say things like
102. 6:39conditioner seals hair against water
103. 6:41conditioner flattens the cuticle  and prevents water from absorbing
104. 6:44effective conditioners actually  stop hair from being hydrated
105. 6:48healthy hair is waterproof
106. 6:50all of this is not really true
107. 6:53if you wet undamaged hair it can absorb about 30%  of its own weight in water in minutes that is a
108. 6:59third of its own weight which is quite a lot
109. 7:02and the reason is if you look at the  structure of hair the F layer is just
110. 7:06sitting on top of each cuticle scale but the  underside and the stuff in between the scales
111. 7:10the CMC these are really good at absorbing  water and it lets it inside the hair there
112. 7:15are just tons and tons of gaps your hair is  basically like a pine cone it is gap central
113. 7:20conditioners stick to hair in little blobs  not one continuous layer these blobs are
114. 7:24small enough that the hair feels soft and  smooth when we touch it but individual
115. 7:29water molecules are really really tiny  they are getting in between the blobs
116. 7:33the blobs also aren't really sticking the cuticle  down or sealing it they are just tiny blobs
117. 7:38but you might be thinking: there  are some tests where it looks like
118. 7:40undamaged hair is waterproof what's  going on there? let's break it down
119. 7:44here's one example if you put a  drop of water on undamaged hair
120. 7:48it stays in a nice round bead  but on damaged hair the water
121. 7:51drop sort of flattens out and it looks  like the water is absorbing into hair
122. 7:55another one is the hair porosity  test you put a strand of hair in
123. 7:58water if it's less damaged it floats  people will say it's "less porous"
124. 8:02but if it's more damaged and it  sinks then it is "more porous"
125. 8:06so if it's not about water absorbing  into hair what exactly is happening?
126. 8:10well this is actually all about surface  tension it's happening because of how
127. 8:13water is clinging to the outside of the  hair not whether or not it gets inside
128. 8:17the way most people explain the strand test  is that hair sinks when it's absorbed enough
129. 8:21water so if it's more porous more holes  the water gets in faster and it sinks
130. 8:26but the thing is hair is already denser  than water you can actually do a similar
131. 8:30test with a paperclip if you're careful  you can get it to float on water even
132. 8:33though metal is denser it should sink  if you poke it or if you add a drop
133. 8:37of detergent it sinks even though the  metal paper clip didn't absorb any water
134. 8:42so both hair and the paper clip are dense enough
135. 8:44to drop down already they'll sink  if you disrupt the surface tension
136. 8:48in a glass the water molecules which are  the blue blobs they really like holding
137. 8:52hands with each other the ones at the  top don't have friends on top so it's
138. 8:56like they have extra hands that have to grab  along the surface and all this bonding all
139. 9:00this grabbing forms a sort of strong skin that  can hold things up like hair and paper clips
140. 9:05normally the oily F layer doesn't like water  it's not going to hold hands with it but if
141. 9:10you get rid of it then you have a surface  that actually likes water it can hold hands
142. 9:14so the water molecules at the top  hold hands with the hair and so
143. 9:17you get less of that surface tension  you don't have a skin the hair sinks
144. 9:21this test still mostly works because  surface damage does largely line up
145. 9:25with other types of damage which affects  how easily other things get into hair like
146. 9:29hair dyes but it isn't actually measuring  porosity in the way that you might think
147. 9:34same with the water drop if you have damaged  hair it absorbs somewhere around 45% of its
148. 9:39own weight in water which it isn't actually  that much more than the 30% for undamaged hair
149. 9:44so the water here isn't soaking inside of each
150. 9:47hair strand it's just spreading along  the surfaces and in between the hairs
151. 9:51so at this point you might be thinking
152. 9:52hang on Michelle if all of this  water is holding hands there's
153. 9:56all the surface tension how is that 30%  or 45% of water getting inside the hair?
154. 10:01it's because it's not liquid water it's gas
155. 10:04so if you think back to high school science  liquids are holding hands they have things
156. 10:07like surface tension but with gases the water  molecules are individual they're far apart
157. 10:12they're separated they're not close enough  to hold hands there is no surface tension
158. 10:16if it's humid enough which it is if your hair is  wet these molecules are small enough that they can
159. 10:21wiggle in in between those cuticle scales into the  hair there's no surface tension getting in the way
160. 10:26now back to the second question: if hair with more
161. 10:29water in it feels rougher then why does  hair feel feel nicer after you wash it?
162. 10:34well the first reason is that water  is really good for spreading stuff
163. 10:37it's way easier to spread conditioner and  water evenly all over your hair compared
164. 10:41to just spreading a much smaller amount of  product which has no extra water to help out
165. 10:46the second reason is water is really good  at resetting the shape of your hair I think
166. 10:51we all know this if you've heat styled your  hair it's gone after you wash it or if it's
167. 10:56a really humid day whatever styling  you do just gets undone a lot faster
168. 11:00this is because heat styling is about breaking  the temporary bonds with heat pulling your hair
169. 11:05into a particular shape and then setting  it which is just letting new temporary
170. 11:09bonds come in and hold the new shape but when  water gets into your hair it breaks the new
171. 11:13temporary bonds and the permanent bonds will  pull your hair back into the original shape
172. 11:18when you wash your hair with lots of heat and  water and shampoo which drops the surface tension
173. 11:24it is really good at breaking lots of temporary  bonds your hair is in a super floppy state
174. 11:29and that gets styled much more easily than usual
175. 11:32it's kind of like candle wax  the more soft and liquid it
176. 11:35is the more flexibility you have to shape it
177. 11:38there's an extra element if you  have curly or coily hair water
178. 11:41is really good at getting strands  to align so that they're parallel
179. 11:45again this is the magic of surface  tension if there's water coating the
180. 11:49outside of the hair it's sticky if  you have two wet strands touching
181. 11:52the water can kind of just  zip the two strands together
182. 11:55this is called self assembly it's a whole thing  in supramolecular chemistry it's really cool
183. 12:00so water helps curly hair clump together which  means they can dry in these nice curl formations
184. 12:05and this can actually make your hair  feel more hydrated when it's dry these
185. 12:09clumps have a bigger surface area that  touches your hand so heat gets transferred
186. 12:13faster they feel colder and smoother  than if your hair wasn't so aligned
187. 12:18it's a lot like how satin feels colder than  a rougher fabric cold things feel kind of wet
188. 12:22it's like how sometimes you can't really tell if  your laundry is still wet or if it's just cold
189. 12:27and this resetting can also happen on  a microscopic level if you dry hair too
190. 12:31quickly like with a hair dryer the cuticle  scales can dry unevenly and some bits shrink
191. 12:36faster than others you end up with buckling of  the cuticle scales and your hair looks like this
192. 12:40this can also happen if your hair gets  stretched a bit about 15% which is not that much
193. 12:46the way to reset this is with water if you soak it
194. 12:48in water then the scales can sort  of reset back into a smooth shape
195. 12:52now you might be thinking isn't this wetting  and drying over and over again bad for your
196. 12:56hair? this is a really persistent myth called  hygral fatigue it's really ingrained everywhere
197. 13:02but there actually isn't that much convincing  evidence that hygral fatigue is actually a thing
198. 13:07the analogy I see is that wetting and drying  your hair is like stretching a rubber band
199. 13:11you do not want to wet your hair every day  because if you are constantly wetting it
200. 13:13and drying it and wetting it and  drying it it will eventually snap
201. 13:16but for rubber bands it's because  you're stretching it so much that
202. 13:19you're breaking permanent bonds  they can't actually form again
203. 13:22in hair water is breaking temporary  hydrogen bonds these ones will reform
204. 13:26really easily so it's actually a  lot more like joining and unjoining
205. 13:30Lego pieces and not the knockoff  Lego the proper brand name ones
206. 13:33except the atoms and hydrogen bonds are way more  durable the electrons and protons never wear out
207. 13:39wet hair is more fragile though so you do  have more opportunity for it to get damaged
208. 13:43if you're rough with it but just having water  going in and out isn't going to cause damage
209. 13:48there are a couple of papers that  seem to say that hygral fatigue is
210. 13:51a thing water itself can damage hair  but they aren't very good evidence
211. 13:55the first one is this study on hair drying  I talked about it in my hair drying video
212. 13:59the researchers concluded that air drying  caused damage because water was swelling
213. 14:03the hair for longer but I don't think  that explanation actually makes sense
214. 14:07air drying is pretty standard everywhere  if it was causing the bulges they saw in
215. 14:11that one little sample of hair then other  studies would be seeing a lot more bulges
216. 14:15so the bulges probably come from something  else that happened to that specific sample
217. 14:19there are also a few studies on coconut oil  that said it could potentially block water
218. 14:22from absorbing so it protects against  hygral fatigue but they don't actually
219. 14:27cite sources for hygral fatigue  being a problem in the first place
220. 14:30with coconut oil a lot of people  including me in the past have
221. 14:33cited this study as a reason for why it  might be good to use before shampooing
222. 14:37but another hair scientist Trefor Evans thinks  this might essentially be a calculation error
223. 14:42in the experiment they put different  oils on hair and then let them absorb
224. 14:45water the weight of the coconut  oily hair didn't increase as much
225. 14:50but it looks like they didn't take the weight  of the coconut oil into account so the same
226. 14:54amount of absorbed water would look smaller as  a percentage you are dividing by a bigger number
227. 14:59and coconut oil not sealing out that  much water this makes sense with hair
228. 15:03structure every cuticle edge is a  gap it's just really unlikely that
229. 15:07you could seal the whole pine cone  against teeny tiny water molecules
230. 15:11and this is the case in general for hair  products it is just really hard to prevent
231. 15:15tiny water molecules going in and out of  your hair the water content of your hair
232. 15:19largely just depends on relative humidity how  much water is actually in the air around you
233. 15:24we already talked about how hair is  weaker and rougher when it's wet and
234. 15:28this is also the case when humidity  is high just to a lesser extent
235. 15:32but having too little water also  causes a bunch of other changes
236. 15:36if humidity is really low your  hair is too dry and static builds
237. 15:39up really easily you get flyaways  that's because hair loses electrons
238. 15:44when it rubs against stuff but water  can help spread that static charge out
239. 15:47so I always notice that my hair  goes really staticky and awful on
240. 15:51planes the humidity there is just ridiculously low
241. 15:54hair that's too dry is also more brittle and  this means it isn't stretchy and flexible enough
242. 15:59you want a little bit of flex  because that absorbs shock this
243. 16:02is important when you are putting  force on it when you're brushing it
244. 16:05dry hair cracks more easily including inside the
245. 16:07hair and when the cracks build up  enough that's when your hair breaks
246. 16:11this also happens with nails if you clip  your nails when they're dry the cracks
247. 16:14will keep traveling because the nails are more  brittle but if you do it after a shower they're
248. 16:18more wet they're more flexible the cracks  will stop they don't spread the whole way
249. 16:22so how do you get your hair into that sort  of happy medium of hydration well there are
250. 16:27a few things that can help or at least  they can make your hair act like it has
251. 16:31a more ideal water content how exactly some  of these things work isn't really settled
252. 16:36bonding treatments I know I need to do a proper  video on these a lot of them seem to work by
253. 16:41sitting in your hair and stopping water from  coming in and breaking a whole bunch of bonds
254. 16:46small molecules like glycerin might be able  to get into hair and act like water or it
255. 16:51could be potentially increasing  humidity right next to the hair
256. 16:54there's a study that found that black  hair at 65% humidity broke more easily
257. 16:59than wet hair and using humectant like  glycerin stopped that from happening
258. 17:03oils like coconut oil the reason  they might work is that they get
259. 17:06into hair a bit and then they make  it more flexible and less brittle
260. 17:09so at the end of all of that  water isn't actually good or
261. 17:12bad it is a tool it can be used  to basically soften hair structure
262. 17:16whether that is good or bad depends on your  hair and what you're trying to do to it
263. 17:20if you want hair that feels smooth and  soft and well cold you probably want to
264. 17:25condition it and shape it so that it is  smoother and the strands are more aligned
265. 17:29it doesn't actually matter if your  product actually says hydrating
266. 17:32you don't need to worry about water damaging  your hair you don't need to avoid washing your
267. 17:36hair or using products with water in them  just to try to avoid this whole concept of
268. 17:40hygral fatigue but you do need to make sure  you treat your hair gently when it's wet
269. 17:44so use lots of conditioner if you're trying  to detangle it whether it's wet or dry
270. 17:48hair science is really complicated and  water is really complicated I have barely
271. 17:52scratched the surface here there are like a  million things like that coconut oil thing
272. 17:56that you have to sort through when you're  reading studies and looking at methodology
273. 18:00back when I was writing my book I wanted to make  a video that was just called "hair science is a
274. 18:04mess" and this shampoo video was what happened  but that is now kind of turning into 10 videos
275. 18:10my hair science playlist is there if you  want to go further down that rabbit hole