How a tattoo works

Nobody explains this to you before your first one, and it makes every other decision easier to understand. So, plainly. Where a claim here has a source, the source is in a note beside it, and where the honest answer is that nobody has measured it in people, the note says that too.

The needle does not inject anything

A tattoo needle is not a syringe. It is a cluster of solid points, soldered together, with no hole in them. Ink sits between the points and on the surface of the skin, and capillary action carries it into the hole the needle opens on the way in.

The machine drives that cluster somewhere between fifty and a hundred and fifty times a second,¹ a millimetre or two down, into the dermisThe second layer of skin, under the surface. It holds the collagen, the blood supply, the nerve endings and the hair follicles, and unlike the layer above it, it is not replaced.. Each pass leaves a column of pigment behind. A line is made of overlapping columns, not of a drawn stroke.

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science-01-skin-cross-section.png
Alt: A cross-section of skin, epidermis over dermis, with a needle cluster at depth and a column of pigment left behind it.
Drawn, labelled, to scale. Hatched, not shaded, per the formal law.

Why it stays

The top layer of skin, the epidermisThe outer layer, the part you can see and touch. It is constantly replacing itself from the bottom up, which is why nothing held in it stays., replaces itself from the bottom up over roughly a month.² Anything left there leaves with it. So the ink has to sit in the dermis underneath, which is not shed.

Getting it there is only half of it. The other half is that your immune system tries to remove it and cannot.

When the needle breaks the skin, the body treats it as a wound and sends macrophagesWhite blood cells whose job is to engulf and digest anything that does not belong. Bacteria, debris, dead cells, and tattoo pigment, which they cannot digest.. They engulf the pigment particles. Some carry it away to the lymph nodes, which is where the ink you lose in the first two weeks goes. Most of them stay put, full of pigment, held in place in the dermis.

Those cells do not live forever. When one dies it releases its pigment, and a new macrophage arrives and eats it again.³ That cycle, capture, release, recapture, is what a permanent tattoo appears to be: not ink sitting inert in your skin, but ink passed between cells that keep failing to remove it.

Why lines get thicker, and why we say no to tiny writing

Every time that pigment is handed from a dying cell to a new one it can land slightly off where it was. Over years the edges of a line soften and creep. Fine detail closes up. Letters with small enclosed spaces fill in and become blots. That last part is not a theory: it is what old tattoos look like, and you can go and look at them.

This is not a failure of skill, and no artist is exempt from it. It is why a tattooer who knows what they are doing will refuse a design that is technically possible today and unreadable in fifteen years, and why traditional tattooing looks the way it does: bold lines, open space, high contrast, readable at arm’s length. Those conventions are not nostalgia. They are what survives the process described above.

If somebody offers you a page of tiny script on a rib at three centimetres tall, they are selling you a photograph of a tattoo, not a tattoo.

Why the sun matters more than anything else

Ultraviolet light breaks pigment molecules apart. The fragments are small enough to be carried off, so a sunburnt tattoo is not just faded on the day, it is lighter afterwards and it stays that way.

Nothing else you do to a healed tattoo comes close. Once it has closed, sunscreen is the whole maintenance routine: SPF 30 or higher, every time. Aftercare has the rest of it.

Coil or rotary

Two kinds of machine, and clients ask which is better. Neither is.

A coil machine works like a doorbell: an electromagnet pulls an armature bar down, that breaks the circuit, a spring snaps it back, and the circuit closes again. It is loud, it is tuned by hand with a screwdriver, and it has a distinct hit that many liners prefer.

A rotary machine turns a motor and converts that rotation into a stroke. It is quieter, lighter, gentler on the hand over a long day, and it gives the same stroke every time regardless of how tired the artist is.

Machines do not make tattoos. The person holding one does.

What it feels like

It is uncomfortable, not agonising, and it changes with where you are. Places over bone with thin skin, ribs, sternum, ankle, elbow, hand, are sharper. Places with muscle and fat under them, outer arm, thigh, calf, are duller. Lining is a scratch. Shading is a hot scrape and is usually the easier part.

The first twenty minutes are the worst because your body has not decided how to feel about it. Adrenaline drops off after two or three hours, which is when long sessions get harder. Eat a real meal beforehand. Do not drink the night before, do not take aspirin,⁴ and tell us when you need to stop, because you can.

Before your first one

• Bring government-issued photo identification. Oregon requires it, every time, for everybody, and we have to keep proof that we saw it.⁵
• You have to be eighteen. A parent cannot consent on your behalf in Oregon; the only exception is a physician’s authorisation.⁶
• Eat, sleep, drink water. Alcohol and aspirin both make you bleed more, and a site that will not stop weeping does not hold ink well.
• Do not bring an entourage.
• Placement, size and composition are the artist’s call. The subject is yours. That is not a power move, it is the only way the thing works on a body that moves and ages.
• Ask questions. Every one of them has been asked before.

Footnotes

1. The usual working range for the machines in a street shop. A coil machine is tuned by hand and a rotary is set by its motor, so the number is a setting rather than a property of tattooing. ↩

2. Estimates for epidermal turnover generally land between about four and six weeks, and they move with the site on the body, with age and with the measurement method. The point that survives the spread is the one made here: the outer layer is replaced and the dermis is not. ↩

3. Demonstrated in mouse skin, not human, by Baranska et al., Journal of Experimental Medicine 215(4), 2018. They tattooed mouse tails, killed the pigment-carrying macrophages, and watched new ones arrive and take the pigment back up. It is the best mechanism anyone has for why tattoos persist, and it is a mouse study. ↩

4. Aspirin stops platelets clumping properly for several days after a dose, which is exactly the thing you want working on a few thousand small punctures. If you take it daily on a doctor’s instruction, keep taking it and tell us. ↩

5. Oregon requires the client record to hold proof that we saw government-issued photo identification, along with your signed acknowledgement of the aftercare instructions. OAR 331-915-0085. ↩

6. OAR 331-915-0065, which prohibits tattooing anyone under eighteen regardless of parental or guardian consent, and allows it only when a physician has authorised or prescribed it. ↩