This episode is sponsored by Tide.
Only use Tide PODS for laundry.
ONLY.
FOR.
LAUNDRY.
Vsauce!
I’m Jake and have you ever stared at your washing machine while it’s cleaning clothes
and wondered...what is happening in there?
Because I have.
And I have a lot of questions.
Because what’s going on behind me are numerous chemical reactions all happening on a level
that can’t be observed by the human eye.
But how does laundry detergent like a Tide Pod, actually clean the multitude of different
stains on clothing?
And why doesn’t the stain from one piece of clothing go into the water and get on all
of the other clothes you have in the wash?
Where does the stain go?
Well, let’s start with water.
Water on its own isn’t very good at cleaning things.
Water has very strong surface tension...it likes to stick with water.
You can see this when you pour water on glass, drops form on it’s surface or when poured
on the ground it pools together.
It also won’t bind with fats or oils.
Try washing a greasy pan with just water...it washes right off carrying very little if any
of the grease with it.
That’s where detergent comes in.
It uses a couple of key ingredients: Surfactants, anti-redeposition polymers, builders and enzymes.
And the enzymes act a lot like the ones that can be found in carnivorous plants like venus
fly traps or pitcher plants or even in our own body.
The main difference is that these are manufactured in giant microbe vats.
Enzymes are molecules that are biological catalysts.
They help certain chemical reactions break down molecules into smaller amino acids.
Now different enzymes break down different things and there are a bunch of varieties
within this little pod but two I want to focus on in particular are Protease and Amylase.
Protease breaks down proteins which are the key components in grass and blood stains.
To see it at work, we need something that is primarily protein...jello.
Wiggle wiggle.
Our jello with water doesn’t do very much but our jello with protease does.
After only a few hours it completely dissolves the entire thing.
Then we get to amylase which is an enzyme that is particularly good at dealing with
starchy stains like gravy, oatmeal or baby food.
Fun fact: amylase is also used in the process of brewing beer/ It converts the starches
into sugars in fermentation.
Ok, let’s see it break down something starchy like cereal.
Again, our beaker with water doesn’t do much whereas with the beaker with amylase
turns the cereal into goo.
In addition to protease and amylase there is also Mannanase to break down thickeners
in foods like ice cream.
And while that's all well in good we still have a problem....water.
That’s where Surfactants and anti-redeposition polymers come in.
Surfactants is short for surface active agents and they basically make water wet better.
What I mean by that is surfactants reduce the cohesion, the water molecules sticking
to each other, and surface tension allowing it to spread across, around and into the fibers
of whatever is being cleaned instead of just sticking together with the other water molecules.
And what is really cool about surfactants is that they a very unusual chemical structure.
The surfactant molecules have a small head and a long tail.
The tail is hydrophobic, it attracts the fat, grease and dirt molecules while the head is
hydrophilic, and attracts water molecules.
The tails stick into the dirt surrounding it, creating a micelle.
This isolates the stains from other molecules and then the head is attached to the water,
suspending the stain particles in that water keeping all of that grime and gunk from reattaching
to the fabric.
And then we have anti-Redeposition polymers.
They’re special polymers that work with surfactants to capture and suspend soil in
the water, basically trapping it.
So that answers our question about why stains don’t just go from one piece of clothing
to all pieces of clothing...
But we’re not done with water just yet because tap water is full of things like calcium and
metals that interfere with the washing process so detergents use builders, water conditioners,
to attract them and keep them out of the way.
Similar to the way surfactants capturing dirt and grime.
And once your clothes have been cleaned by enzymes and builders and surfactants there
is one more chemical process.
Let’s turn the lights off.
If we shine a flashlight on a tide pod it...looks normal.
But if we switch our flashlight to a UV light...this happens.
It’s optical brighteners.
They absorb UV light and re-emit it in the visible spectrum making your clothing brighter.
When that UV light is re-emitted it does so in the blue visible spectrum which makes things
appear whiter by changing the color temperature of light.
And optical brighteners aren’t just found in detergent, they’re used in paper, cosmetics
and in plastics like your nice super white looking phone charger.
Look at my teeth.
My toothpaste has brighteners.
If I had to venture a guess, some of the clothing you’re wearing right now was made with brighteners
in it so all detergent does is replenish what gets washed away when you clean your fabrics.
This is why if you’ve ever been in a place with a bunch of UV or black lights, you’ve
probably noticed how white shirts glow.
It surprised me how much is actually happening in your washing machine because form the surface
it looks so straightforward.
And it wasn’t until years ago when I read Mary Roach’s incredible book that I realized
what a clever and complicated bit of science is happening in there.
I would highly recommend reading this book if you haven’t.
Mary interviewed a P&G researcher, the folks who make Tide, which is what lead to me talking
to researchers there as well.
So thank you to Tide for finding this topic interesting and wanting to support Vsauce
and this video and, as always, thanks for washing.