it's michelle here from lab muffin
beauty science and today i'm going to go
all hot and cold on you have you heard
that putting beauty products in the
fridge will make them last longer
why does cooling products down make them
go off slower why not put them in the
freezer can you make them too cold
let's have a look at the science behind
what happens when you cool down a beauty
product if you own skincare and
makeup products you'll probably have had
one or two go off at some point
sometimes it's really obvious it might
change color it might have a funny
texture it might have a weird smell it
might even have a spot or two of mold in
the corner sometimes it's a lot less
obvious and you only know because you
try it on and it causes you to break out
or have a rash and then there are some
products that never seem to go off like
petroleum jelly or a jar of clay powder
so what's actually happening when a
product goes off the answer is usually
chemical reactions most of the time when
a product goes off it's because the
ingredients are changing while on the
surface it seems like nothing is
actually happening when you look at it
if you look microscopically if you zoom
into the atoms and molecules you'll see
lots of little changes happening at any
temperature above absolute zero or minus
273 degrees Celsius or minus 460 degrees
Fahrenheit if you're a heathen
everything is vibrating with energy when
you heat something up all the
microscopic particles vibrate faster for
a chemical reaction to happen what needs
to happen at the microscopic level is
that chemical bonds need to break this
way the atoms can rearrange and turn
into new molecules if there's a chemical
reaction that involves more than one
molecule the molecules need to hit each
other hard enough that the bonds will
break if they don't hit each other hard
enough then the molecules will just
bounce apart without reacting in your
beauty product you don't want reactions
to happen if you have a product with
vitamin C or ascorbic acid for example
you want it to still be ascorbic acid
when you put it on your face
if you heat up the molecules then
they're vibrating more and moving faster
which means when they hit each other
they'll hit each other harder and more
reactions will happen faster it's a bit
like two people bumping into each other
if they're walking they'll probably just
bounce apart without getting injured but
if they're running then there's a good
chance they might break a bone or two
now imagine that instead of just having
two people we have millions of people
walking around bumping into each other
most of them will probably bounce apart
without getting hurt but every once in a
while someone might lose balance and
fall over and break a bone or someone
might bump into someone in a weird way
and jar their finger if we wait long
enough eventually everyone will get
injured now let's make everyone jog
again most people will bounce apart and
not get hurt but this time injuries are
going to be more likely there'll also be
more collisions because everyone covers
more space in the same time so everyone
again eventually gets injured but it
happens a lot faster now let's make
everyone sprint most collisions will
cause injuries and everyone covers a lot
more ground so we get a lot more
collisions as well it probably won't
take much time for everyone to get
injured it's exactly the same with
ingredients in your products instead of
people we have molecules and we make
them move faster by heating them up by
the same logic we can make the molecules
move slower by cooling it down and
that's where your fridge comes in there
are a few reactions that don't involve
collisions but they'll still work almost
the same way decomposition reactions
where a molecule falls apart also speed
up at higher temperatures if you have
say a Lego statue and you shake it
harder it will break faster
even when your product grows bacteria or
mold it's again because of chemical
reactions every living thing is powered
by chemical reactions including humans
with bacteria and mold it can be a bit
more complex as well most organisms have
a temperature range in which they
function the best and if you go outside
of that range like by cooling it down
then they don't function as well
they don't multiply as quickly and so
your product will go off slower one way
that products can go off without
chemical reactions is when the texture
changes most beauty products are
emulsions which look a bit like this for
example they might have droplets of oil
sitting in water with surfactants in
between to hold it in place now as you
probably know oil and water don't like
each other and this type of emulsion
forces the two to come into contact
with each other quite a lot they'd much
rather be apart the surfactants help
them hang out for longer but eventually
they want to break free and separate
like oil and vinegar in a vinaigrette
salad dressing if it's at a higher
temperature then there's more heat
everything moves around more so the
molecules will have more energy to break
free of the emulsion structure and ends
up separating faster so if putting your
products in the fridge will make them go
off slower why not put them in the
freezer well a lot of the time freezing
products will actually be better for
these reactions and slow them down more
but it's those tricky emulsions again
freezers are cold enough to freeze water
they're below zero degrees Celsius if
you've ever made ice cubes then you'll
know that water expands when it freezes
into ice and this expansion happens when
you cool it down relatively slowly in
your domestic freezer water molecules
also like to come together when water
freezes this means that a lot of the
time when you freeze a product and then
defrost it where the water is located
will change for example if you have a
product that contains some whole plant
cells
the water will Hulk out and burst the
cells giving you a mushy texture this
happens with things like fresh face
masks
and lots of fruit and vegetables as well
more importantly for beauty products
it's those pesky emulsions again what
happens is when water freezes it freezes
from one side of the product to the
other the expanding ice squeezes the oil
droplets together and this makes the
emulsions separate so when you defrost
it it wouldn't have the same texture you
might have experienced something similar
if you've ever drunken a frozen bottle
of drink before it defrosted completely
it starts off super sweet because all
the sugar and flavors have come together
but at the end you're left with a bland
block of ice there's a cool video from a
recent science paper that used confocal
microscopy to see what happens when
an emulsion gets frozen slowly if you
freeze the product fast enough this
isn't an issue because the droplets
don't have time to come together and the
ice doesn't have time to expand as much
this is why frozen food from the
supermarket usually ends up less mushy
when you defrost it than food that
you've frozen yourself
it's also why liquid nitrogen ice cream
ends up so smooth it's because it's got
tiny crystals because the crystals
haven't had time to expand but this
isn't really possible with the
temperatures in your home freezer the
other issue when you freeze a product
and move the water around is that you
can also change how well the
preservative system works if the
original product was formulated properly
there would be effective levels of
preservative throughout the whole
product but if the water is moving
around there'll be some areas where
there's more preservative and some areas
where there's less preservative and the
areas where there's less preservative
can become under preserved which means
that bacteria and mold can grow more
easily
if you don't mind the texture change and
you mostly just care about keeping the
active ingredients intact and you only
defrost enough that you can use quickly
before mold and bacteria start growing
then freezing your products is fine for
example it takes me ages to use up a tub
of lush's angels on bare skin scrub
but it goes off after a few months so
what I do is I freeze it in little lumps
that I can use up within a few days and
so I defrost one lump at a time each
lump goes off after about a week and it
becomes super runny instead of nice
and solid but it doesn't make too much
of a difference when I'm using it on the
other hand if there's a product where
the texture is really important then you
probably don't want to freeze it for
example the microscopic emulsion
structure of a sunscreen is crucial to
how well a sunscreen works freezing it
is going to mess up the structure and
change the concentration of the
sunscreen ingredients in the different
parts of the sunscreen foundation is
another example where texture is super
important to how well it applies on your
skin so again you probably don't want to
freeze it there are also some products
that contain proteins called enzymes and
in some cases enzymes can become
denatured when you freeze them and this
is where the enzyme changes shape and so
it stops working but the ones most
commonly found in skincare products
bromelain from pineapple papain from
papaya aren't affected much by freezing
so that's fine that's all from me today
about freezing your beauty products I
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see you next time for more beauty and
science
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