تدريب Shadowing: Stop drying your hair wrong: the science - تعلم التحدث بالإنجليزية عبر الفيديو

what's the best way to dry your hair according to science is it hair dryers hair straighteners towels

or just leaving it to dry naturally i'm michelle i'm a chemistry phd

and cosmetic chemist

and as someone with fragile expensively damaged hair who tries a

lot of hair products i have a special interest in this

here's the science of drying your hair first we need to talk about what happens

when hair gets wet how hair interacts with water hair has

a complicated structure with lots of different parts most of these like water especially the inside

which is called the cortex so when your hair is properly wet like

when you're washing it it swells up undamaged hair can absorb

up to about a third of its own weight in water

damaged hair has more gaps for water to fill sort of like a more bubbly sponge

so damaged hair will hold on to even more water

and what water does really well is break hydrogen bonds your hair is held together by lots of bonds

which give it its strength

and shape some of these are pretty permanent they only really break with chemical treatments

but hydrogen bonds are temporary they break

and reform all the time about a third of your hair strength comes from these temporary hydrogen bonds

when your hair is dry hydrogen bonds are sticking hair proteins

to hair proteins it's sort of like they're holding hands they're essentially glued together at a molecular level

but water can also form hydrogen bonds so

when your hair is wet your hair proteins start bonding with

the water instead of with each other these are a bit like you

and your dog are at a dog park you have a strong bond he comes

when you call him timmy

but adding water is like adding a whole bunch of really

friendly puppies you're both having interactions with all of these new puppies you

and your dog have a temporarily weaker bond but

when these other water slash puppies leave the hair slash park you

and your dog have a stronger bond again now looking at

this diagram can you see the problem the water isn't attached to anything

so the two halves of this hair protein ladder have broken

rungs they are less glued together i will never run out

of analogies for this less hydrogen bonds holding everything together means

that your hair is weaker you can actually test this for yourself try stretching a strand of your hair

when it's wet and a strand of your hair

when it's dry the wet hair will be stretchier feel free to pause this video

and try this out i will still be here

when you come back i promise on top of this the

cuticle scales in your hair those overlapping roof tile scales on

the surface they don't absorb water evenly the underside of each scale absorbs more water than the top

and the glue in between the scales also absorbs water this means

that the bottom expands the scales get pushed up away from the hair they stick out more

and they get snagged and chipped more easily

so water in itself isn't really damaging to hair you might

have seen some stuff online about hydrog fatigue the idea

that just water will damage hair but the evidence doesn't really show

that water on its own has much of an impact but

when your hair is wet it is in a more fragile state

so anything that you do to your hair physically

that can cause damage if you do it when it's wet

that damage gets magnified there are exceptions one really big one is detangling curly hair check out my old video

that explains this so what all of this means for drying wet hair with any method

that you use technique will make a massive difference.

Rubbing your hair with a towel like you're trying to start a fire is very different from blotting and squeezing it gently.

You can imagine those little sticky up hedgehog spine cuticle scales bashing against each other.

Yanking your hair violently with a round brush

while using a blow dryer is very different from gently spreading out your hair with your fingers

and moving it around even with leaving your hair to air dry naturally sleeping on wet hair

and smushing it into your pillow with the full weight of your galaxy brain

or having your hair jammed between your back

and the couch as you watch a stressful movie that's very

different from letting your hair dry in peace the other really

big thing we need to talk about is heat heat can

cause a lot of different types of hair damage proteins in your hair can change shape

or break down which makes your hair weaker substances inside your hair can oxidize

and change color this can make your hair look yellow and

if you have dyed hair the dyes can break down

and change their color heat can cause microscopic cracks

and cavities in your hair especially at the surface

and your cuticle scales can lift this makes your hair rougher

and duller but on the bright side it can make your hair less oily

because the gaps can hold onto oil see there can be upsides to damage

and we need to talk about bubble hair if your hair is wet

and you heat it near the boiling point of water above

about 90 degrees the water inside the hair can evaporate faster

than it can escape it boils explosively it basically punches its way out of your hair

and leaves bubbles inside your hair is basically popcorn like

and subscribe if you want the algorithm to give you more analogies that

i will probably regret one day

when someone takes them out of context with all of these types of damage the more heat

that you use the worse it gets and there are some changes

that don't happen until you get to a particular temperature usually

you get a ton of damage from about 180 degrees yes

that is celsius i do not rock with fahrenheit

so using a standard hair straightener on wet hair is one of the most damaging ways to dry your hair

if you're hearing snapping and crackling that is water boiling quickly

and some of

that might be the water inside your hair turning it into rice bubbles blow dryers aren't anywhere near as hot

so the level of damage is very different you probably don't need to use heat protectants either

when your hair is still wet the water evaporating helps cool down your hair

so it doesn't usually heat up too much plus all

that air also helps your hair dry it's best to move

the dryer around to try to dry your hair evenly

so you're not like heating up already dry strands for no good reason the distance between the dryer

and your hair also makes a really big difference like in this study the researchers washed

and dried hair samples every day for 30 days with different drying methods there's just leaving it to air dry

and then using a hair dryer at different distances the further away the hair dryer the lower the temperature

and the longer it took to dry they found

100

that all of the samples

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that were dried with the hair dryer had damage to the

102

surface of the cuticle with higher heat causing more damage the cuticle scales lifted

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and cracked there were also signs of bubble hair at a distance of five centimeters

104

which is about this much this translated to a hair temperature of 95 degrees

105

and this agrees with other studies the cracking is thought to be

106

because hair makes the outside cuticle dry faster than the inside cortex

107

so the outside is drinking faster than the inside the inside kind of hulks out

108

and cracks the cuticle around it

109

and there have been reports of bubble hair with hair dryers

110

but they're usually when the hair dryers are used really close

111

so the hair gets really hot most of the time it is the hotter curling irons and straighteners

112

that have the risk of like properly swiss cheese hair with

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really big holes there is a weird finding in this hair dry study the hair

114

that was left to air dry had some bulges in the cmc

115

that is the glue that's sticking the cuticle scales together the author suggests

116

that the cmc might be swollen and damaged

117

when it's wet for too long which led to their conclusion

118

that using a hair dryer is less damaging than air drying this hasn't been replicated as far as I know

119

and I don't think their explanation makes a lot of sense they use 20 centimeter long human hair

120

which is about this much which is about a year

121

and a half of growth so you would expect

122

that all the hair would have been washed

123

and air dried at least 30 times before it was collected

124

and then used in the study but only the air dry sample had bulges

125

so I suspect that something else happened to the hair like maybe

126

that sample came from someone who had a lot more sun exposure or

127

something unusual happened during the study so I just don't think the idea

128

that air drying is more damaging is really supported by their

129

results although air drying does leave your hair in a wet fragile state for longer

130

which shouldn't be a problem in this lab setup I think

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I've quoted before on this before i knew as much about hair science

132

and before i really had the confidence to interpret these studies more critically

133

so i have changed my mind on this sorry i am

134

human i get stuff wrong now damage isn't the only thing

135

to think about sometimes hair damage is worth it bleach is

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one of the most damaging things you can do to your

137

hair i have bleached my hair from black to white three times

138

and i'm going to keep doing it

139

but i think it is important to know what the risk actually is

140

so you can work out whether it is worth it for you

141

so here are some of the things you might want to

142

consider apart from damage first off styling you might have noticed

143

that washing resets your hair's shape and like hair strength this is

144

because of bonds hair is held in a particular shape by permanent

145

and temporary bonds again this is like glue

146

when your hair gets wet water comes in

147

and breaks a whole bunch of hydrogen bonds

148

if you then keep your hair in a particular shape as it's drying the new hydrogen bonds

149

that form will hold your hair in the new shape but

150

when you wash your hair water again comes in

151

and breaks the hydrogen bonds the permanent bonds pull your hair back into its original shape

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so that's what you get

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when it dries unless of course you hold it in some

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unnatural shape again your hair also slowly goes back to its original shape over time even

155

if you don't wash it that's because heat

156

and humidity will also break temporary bonds different techniques work best to get particular styles

157

and some of these like blow drying will work better

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if you use heat to dry wet hair yes this is

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another lovely diagram from my very nicely illustrated book the science of beauty

160

which should be available by the time this video is out the link is on the screen

161

and in the description this video is based on some of

162

the info in it i think you'll really enjoy this

163

if you want science-based practical advice i also debunk a whole

164

bunch of common myths in it it covers hair obviously

165

but also skin nails makeup and general beauty things like reading ingredient lists what the risks are with specific ingredients sustainability

166

so many topics including dandruff

167

if your scalp is prone to dandruff it might also be a good idea to dry quickly

168

which means using heat one of the big contributors to dandruff

169

is an overgrowth of a fungus called malicezia furfa this is naturally on your scalp

170

but it can cause issues

171

when there's just too much air drying leaves your scalp down for longer

172

which is perfect for this fungus to grow and it is even worse

173

if your hair is wet

174

and then you trap the moisture you slow water from from evaporating even more with something like a hat

175

or a helmet you might also want to consider this even

176

if you don't have dandruff

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but your scalp is irritated overgrowth of this fungus can cause irritation before any visible dandruff actually shows up

178

and of course there is the question of time and effort

179

and where things fit into your routine microfiber hair towels

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and turbans can really help speed up drying with minimal effort

181

and minimal damage these are made of a water absorbent material

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that can form hydrogen bonds

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and it goes through a special extrusion process to create a

184

really big surface area the way towels work is you touch the towel to your wet hair

185

and the water has two choices it can stick to your hair

186

or it can stick to the towel

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if the towel has more hydrogen bonding sites

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that aren't already holding onto water compared to your hair then

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the water will stick to the towel the really big surface area on these towels means

190

that you have more of these exposed hydrogen bonding sites basically

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there are more hands for water to grab onto hydrogen bonds are

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so underrated they explain like everything i love hydrogen bonds you can quote me on

193

that blow drying is more effort and potentially more damaging

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because of the heat depending on how you do it

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but it is faster and on the scale of things

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that damage your hair it's really not on the same level as like oxidative chemical treatments like bleach

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and permanent dye there are also wet to dry straighteners

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that are meant to combine drying

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and styling in the one step a lot of these claim

200

to be less damaging some of them even claim they cause

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no damage they use things like lower temperature plates hot air sensors

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that adjust the temperature in real time i think some of

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these do seem like they'll be at least a whole bunch

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less damaging than using a regular straightener on wet hair but

205

i don't think they're likely to be less damaging than gentle blow drying

206

or just air drying but they are faster and more convenient

207

so again it's a compromise so at the end of all

208

that here are the key points air drying using a hair dryer on low heat

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and gentle towel drying are probably the least damaging ways to dry your hair

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when your hair is wet it is more prone to mechanical damage so

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if you're going to be rubbing your hair against something like

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a pillowcase it's probably going to be best to dry it

213

as much as you can first as well as damage you might also want to think about time effort hairstyle

214

and scalp irritation or dandruff

215

so this is my personal compromise let me know what yours

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is i try to wash my hair a bit earlier in

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the day i avoid washing it after about 7 pm

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because bleached hair holds onto water a lot better and

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so it needs a lot more time to dry properly

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if i go to bed with my hair damp my hair dries rough and bent

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and it gets damaged i can literally see more split ends

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the next day i blot it with a normal towel

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and then i squeeze

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and wrap it with an aquas microfiber towel for about five minutes i can't really leave this too long

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because it makes my fringe dry in a weird way

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and i cannot style my fringe for the life of me without properly wetting it

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and letting it air dry in winter it takes longer for my hair to dry

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and dandruff is usually worse in winter for like everyone i don't really get much dandruff anymore

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but i do get scalp irritation

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so i dry the hair around my scalp with a hair dryer i'm still using the panasonic one

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that i talked about in this sponsored video it has a scalp mode

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that is the perfect temperature for not hurting my scalp then i let my hair air dry

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if it's still damp a few hours before bed then i will use my hair dryer again

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which has really good heat control i move it around a lot to try to dry it evenly

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and avoid hot spots i try to do this early

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so it still has tons of time to dry properly

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and then if it still isn't properly dry

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and i need to go to bed then i will blast it again there are

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so many myths about hair online i debunked a whole bunch

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of these recently in this video my book also debunks a

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whole bunch of hair myths the link is on screen i

242

have a whole bunch of beauty science videos my hair science playlist is here for your viewing pleasure

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كيفية فهم المصطلحات العلمية المتعلقة بالعناية بالشعر.
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التركيب	في الفيديو
المبني للمجهول be + اسم المفعول — التركيز على ما يحدث لا على من يفعله	is called · is held · isn't attached
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جمل الوصل who / which + جملة — معلومة إضافية عن شخص أو شيء	down which makes · much which is · someone who had

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تدريب Shadowing: Stop drying your hair wrong: the science - تعلم التحدث بالإنجليزية عبر الفيديو

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