One of the most ancient and personal forms of art is the tattoo: getting a permanent piece of attached to your own body.
But as someone who has never had a tattoo before, I was fascinated to learn exactly how you can get something permanent into your skin that doesn’t fall off as you grow new skin. It’s a completely different way of producing art than spreading colour on a canvas.
And as a science geek, I was even more impressed to find out the high-tech ways that lasers can remove it, and what happens to it during the process.
Watch the video above to see in super-slow motion exactly how a tattoo needle creates the pattern, at 3,200 frames per second. It is oddly mesmerising. And it’s made by the great guy at Smarter Every Day which already showed us how our brains can become fixed in their way of thinking (with a backwards bicycle).
Then watch this video below to find out the physics and chemistry of how it works, and how the removal process using lasers works.
Essentially, tattooing works by breaking through the outer layers of skin ith a series of very small needles, which carry ink particles down into the deeper layers of skin.
The fact that they are particles is important.
You see, when your body notices a foreign object inside it (like a bacteria, grain of sand or ink particle), it sends in specialised white blood cells which attack the foreign object by “swallowing” it, and then moving it to the body’s filter systems (liver) to be removed (i.e., you poop it out).
But the white blood cells can only swallow objects that are smaller than they are. Some of the ink particles from the tattoo will be small enough to be swallowed and removed, leading to less ink in the tattoed area. This is why tattoos fade over time.
But the larger particles are too big for the immune system to get rid of, and so they stay there permanently.
Laser tattoo removal works by shining a very intense but extremely short (1 picosecond, or 0.000000000001 seconds) burst of laser light through the skin. This heats everything for s short period of time. Your skin isn’t affected too badly because the water in your body can distribute the heat, and the skin can heal. But the wavelength of the laser light is tuned to affect the larger ink particles. It causes the particles to heat up so quickly that they experience a process called “thermal shock”, which makes them shatter (the same thing happens if you put a hot piece of glass in cold water).
Now, the shattered large particle has broken up into several smaller particles, which may now be small enough for the white blood cells to carry away.
Makes sure to watch the second video at 7:00 minutes, when you can actually see the dark tattoo almost disappear.
And in the end, what happens to that tattoo you had removed?
You poop it out