How exactly do tattoos stay on your body?

Today’s Video of the Day comes from the American Chemical Society’s Reactions series and features an in-depth look at the science behind tattoos.

Human beings have been tattooing themselves for thousands of years. Many different ancient civilizations treated tattoos as an art form and used a number of naturally occurring ingredients to get the job done. Tree bark, copper, ash, graphite, and woad were used before ink technology evolved.

In order to place the tattoo on the body, a solid pigment color must be suspended in a liquid carrier such as water, witch hazel, propylene, glycerin. Alcohol can also work as a liquid carrier, including anything from ethanol to vodka to mouth wash.

But how do tattoos stay on your body permanently even as your skin cells die off?

Skin cells live for an average of 2 or 3 weeks. Tattoo needles containing the ink puncture the skin 50 to 3,000 times per minute. The trick is to get the ink through the top layer, known as the epidermis, and into the base layer, called the dermis. This process is aided by capillary action, where surface tension causes a liquid to fall deeper into an absorbent material.

Then, the body’s immune system kicks in to try and close the “wound” by releasing macrophage cells. These cells eat up the ink in an attempt to dispose of it, but then get stuck in place inside the dermis. The inked-up macrophage cells stay inside the dermis permanently, which is how the tattoo stays on the body.

Remember, it’s permanent. So make sure you really want that person’s name or that generic symbol attached to your body for the rest of your life.

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By Rory Arnold, Earth.com Staff Writer

Source: American Chemical Society