Hey it's me Destin
Welcome back to Smarter Every Day.
So in the last video we talked about what it
was like to get a tattoo in slow motion.
But this time we're gonna talk about the
removal process. It's way more complicated.
It involves physics like thermodynamics,
optics, even biology and chemistry are involved.
So today on Smarter Every Day we're gonna go
get some ink and then go to a plastic surgeon
and see if we can get it removed. Check it out.
(Destin) Can I steal some ink?
- [laughs] Thanks. Yes.
So before we talk about how to get the ink
out of the body let's talk about what exactly
you're putting into it.
Most people don't realize this but the bright
colors in tattoo inks are actually created from
compounds that mostly use heavy metals.
I know, that's kind of crazy right?
I mean, you go to all these great lengths at a
tattoo parlor to have a sterile field so no
pathogens transfer, but if you think about it,
they're essentially making a very clean way
for you to inject heavy metals into your body.
It's kind of crazy if you think about it.
Anyway, let's go talk to a smart guy.
OK, so we we want to know how to remove
a tattoo with a laser so we're here with Dr Lappert,
- Yes, so I have some questions.
You've got some big machines beside you here,
- I'm assuming these are lasers?
- Yes they are.
This one over here is an ultra short pulse laser
that we use for the tattoo removal.
- We're talking nanosecond level?
- No. Even shorter than that.
- Picosecond level.
- So a decimal point, eleven zeroes, and then put a digit
in there somewhere and you've got picosecond time scale.
So this is.. this one here is an alexandrite laser,
and alexandrite lasers are sort of tuneable within a
certain narrow frequency range but we're gonna
be operating at about 755 nanometers with this thing.
- Oh wow. So that's just in the infrared right?
- Alright before we start zapping stuff I want to
know exactly what it is we're going to zap.
I've got a little drop of tattoo ink here and
I'm gonna put it on this slide and place
it under my microscope in hopes that we can
see those metals.
When we zoom in you can see these little bitty
ink particles moving around, and then there's
these much bigger chunks.
Take just a second before we go further
and remember what that slow motion tattooing
I recorded in the last episode looked like.
Alright, now that we know what the ink looks
like mechanically, we can draw a better picture
of what's happening.
Multiple needles are puncturing your skin
and dragging both big and little ink particles
down through the epidermis into the dermis.
- From the moment the tattoo is placed however
your body's trying to get rid of it.
Your body recognizes that it's foreign material
as if you got a sliver under your skin.
So your immune system is coming over
looking at this stuff going "hey this
doesn't belong here".
White blood cells come in to remove the pigment.
Now the white blood cell is a very small little cell
whereas the pigment granule is a relatively large
structure if you looked at it under the microscope.
That white blood cell actually comes over and
tries to engulf the pigment granule, and because
the white cell is so small and the pigment granule is
so big, that munching away is a very difficult thing.
It's like trying to take a bite out of an elephant.
- Alright, so this is about to get weird but I have to do this.
I want to know how big my blood cells are relative
to the ink particles.
So obviously we have to prick my finger and get some
blood and put it in there with the ink.
Alright here we go and we put the microscope
slide in and it is more awesome than I
thought it would be.
It is, look at it.
So we've got blood cells interacting with ink
so we can see the relative scale of the two right?
So we've got these little bitty ink particles
that are smaller than the blood cells
and we have the larger ink particles that
are larger than the blood cells.
That means the small ones can be drug away
by the phagocytes or the white blood cells,
but the larger ones can't.
That's why tattoos are permanent,
but that's also why they fade right,
because part of the ink is drug away
but part of the ink stays.
That's like so awesome.
- If you look at a freshly placed tattoo,
it looks very sharp, it has very clean edges,
very clear colors, very crisp.
- If you look at a tattoo on a retired master gunnery sergeant
from the marine corps, that tattoo's starting
to look faded.
- Because what's happening is that pigment is being eaten
by those white blood cells and carried through
the lymphatics of the skin, because it's headed for
your liver, and that process has been going on
in the gunnery sergeant for 35-40 years.
- I find that hilarious that you're picking on gunnys
because I know a couple of gunnys.
- Well I'm retired navy.
- Oh so you're allowed to say it.
- Oh yeah I served the marine corps for years.
- OK good.
- The problem is that the relative size of the
white blood cell and the pigment granule,
big pigment granule, little white blood cell.
So what the laser does, is if you have the
right type of laser when you hit it with a pulse
of light, hit the pigment granule with a pulse of light,
that pigment granule will shatter, OK.
And so as you shatter the pigment granules
you're making them smaller and more edible.
- So you're accelerating the speed with which
the white blood cells, and the efficiency with
which the white blood cells can remove the pigment.
- So they're trying to take it to the liver.
- Correct. That's the way out.
- So you're gonna zap the ink with this laser.
- And then the white blood cells are gonna go
grab the broken up ink particles and
take it to the liver.
- That is correct. Through the lymphatic
channels of the skin, into the larger lymph
channels deeper down, and ultimately
through the liver for cleaning up and excretion.
- So how does an optical energy source
shatter a mechanical ink particle?
Think about this.
Let's say we have a heat lamp, and we
turn it on and we shine radiation energy
on one side of an ink particle.
What's gonna happen is it's gonna heat up
that side and then the heat transfer
coefficient is gonna cause the entire ink particle
to heat up from this side towards this side right?
There's gonna be a heat gradient.
What if we had a really really really hot heating lamp
and it was very very fast.
Assuming the laser and the ink are the right color,
this laser will shine on one side of the particle
and heat it up so fast that only that side grows
due to thermal expansion.
The other side however doesn't have time to catch up,
so it's still cool which causes huge internal
stresses which rip apart the particle.
That's why it's a time game.
The faster you can heat up one side relative
to the other, the more likely you can rip apart the ink.
The more exposure time, the more tissue you affect.
- But the smaller exposure time, the more
localized if you hit the right chromophore.
- I feel like I know the big words now. [laugh]
So once it's shattered, the white blood cells
are gonna come get those little broken
particles of ink, take it to the lymph nodes
then dump it off to the liver and then you're
eventually gonna poop out your tattoo.
That's how it works.
- The aiming beam is a helium neon laser,
very low energy but it allows me to see where the
actual pulse is gonna go.
Alright you ready?
- I am now ready.
- OK here we go.
I'm just gonna keep treating while you...
You can see what I mean about the
- I do.
- How it elevates the top layer of skin there.
- So there you go.
That white effect that you're seeing
is called frosting, and it only lasts for
just a few seconds. It's basically a shock
wave that's happening at the particle level.
Dr Lappert says that depending on the color
this could take just a few treatments
before the body can fully process the ink.
Alright so I hope the take away from this
episode was, if you're gonna get a tattoo,
know exactly what you're doing.
What are you getting tattooed into your body,
meaning chemically what are they putting
into you, and also what is the design.
Think it through because it's a lot harder
to get a tattoo off than it is to put it on.
Think about it.
Alright, so if you enjoyed all the sciences
in this episode, optics, thermodynamics,
chemistry. You will enjoy this audio book
I'm about to recommend.
Many of you know that Audible.com
sponsor Smarter Every Day, but you
just need to listen to this book, I don't
care how you do it. If you go to
audible.com/smarter you can get
this book for free. It's called
The Martian by Andy Weir.
This book is incredible.
You just need to listen to it.
I would love to be the guy that
introduced you to it, but you just
need to experience it on your own
because he's stranded on mars and he
has to MacGyver himself off.
Think about that.
We're talking like radio electronics,
orbital mechanics, rocket propulsion,
chemistry, biochemistry, thermo.
Anyway, The Martian by Andy Weir,
I really really really enjoyed it.
If you liked this episode you're
gonna like it too. So there you go.
Please experience that, and you can
thank me later. However don't do
what I did and start the book with your
two year old in the car because there's
a little bit of cussing. I apologize about that
but I think it's worth it.
I hope you enjoyed this episode and it
earned your subscription.
If not, thank you anyway for watching,
I really appreciate that.
I'm Destin, you're getting Smarter Every Day.
Have a good one.
If somebody's going to get a tattoo removed,
what are the questions they need to ask,
- How long will it take me to drive to Dr Lappert's office.
We will leave it with that. There's your doctor..
Dr Lappert, plastic surgeon. There you go.
You are something else man.