Tattoos are forever. Until you zap them really quickly with a powerful, skin penetrating laser.

A few weeks ago, YouTube science channel Smarter Every Day broke down the violent but beautiful process of getting a tattoo. In short, a needle drives through the outer layer of your skin, making thousands of holes which pull ink down into your dermis.

A tattoo’s permanence comes from this ink. It contains particles of heavy metals which give it strong, bright colors. It also means that your body recognizes a tattoo as a foreign object and tries to get rid of it by sending white blood cells to attack the ink intruder and process it out of the body.

But this is easier said than done because the ink particles can be big. White blood cells can easily attack and carry smaller ink particles away through the lymphatic system to be cleaned out by the liver, but they can’t exactly get a good bite out of the big ink particles. Keep that in mind because here’s where the process of tattoo removal comes in to give those white blood cells a hand:

The process of removing a tattoo isn’t really removing it, it’s breaking down the ink’s metal particles so the white blood cells can “eat” them. In short, it’s thermodynamics.

When you shine a light on a metal particle, that particle will get hotter on the side facing the light but will eventually heat all the way through. But not if the blast of light is hot and fast. A hot and fast light pulse, like one from a laser, will heat the metal particle unevenly. Thermal expansion says this one side of the particle will expand while the other doesn’t; the short pulse means the heat from the light can’t get all the way through the particle. So the particle splits.

Splitting the metallic ink particles with a light makes them small — small enough that white blood cells can finally get a good grip on them and carry them to the liver. Here the ink particles are processed with all the rest of the waste. You will, essentially, “poop out your tattoo.”

—

Feature Image: Smarter Every Day/YouTube