Tattooing – how does it work?

A tattoo is ink trapped in the second layer of the skin. Everything else — the machine, the needle, the artist’s technique, the aftercare, the healing process — exists to get the ink to that layer and keep it there. The process is mechanical (a needle punctures the skin and deposits pigment), biological (the body reacts to the wound and to the foreign material), and — over the long term — a negotiation between the ink’s desire to stay put and the body’s slow, patient effort to remove it.

Understanding how tattooing works at the level of needles and tissue is useful for anyone who has a tattoo, is considering one, or makes them. It explains why certain techniques produce certain results, why tattoos age the way they do, why some placements hold better than others, and why aftercare matters.

Human skin has three layers. The tattoo lives in the middle one.

The target zone for tattoo ink is the upper to mid dermis, at a depth of roughly 1 to 2 millimetres below the surface of the skin. This is the zone where the ink is deep enough to survive the epidermal turnover cycle but shallow enough to remain visible through the translucent epidermis above it. Placing ink consistently at this depth, across different body parts with different skin thicknesses, is the fundamental technical skill of tattooing.

Tattoo needles come in standardised groupings, and the grouping determines what kind of mark the needle produces.

Round liners (RL). Needles arranged in a tight circular cluster, used for line work. A 1RL is a single needle — the finest possible line. A 3RL is three needles in a tight triangle. A 5RL, 7RL, and 9RL produce progressively thicker lines. The tighter the grouping, the crisper the line. Round liners are what draw the outlines that define most tattoo styles.

Round shaders (RS). The same circular arrangement, but with slightly more spacing between the needles, allowing the group to deposit ink in a broader, softer pattern. Round shaders are used for shading, colour packing in small areas, and smooth gradient work.

Magnum configurations (M1, M2). Needles arranged in one or two rows, used for filling large areas and for broad shading. A stacked magnum (M2) has two rows of needles stacked on top of each other. A flat magnum (M1) has the needles arranged in a single flat row. Magnums cover more skin per pass than round configurations and are essential for filling solid colour fields and laying smooth greywash gradients.

Curved magnums (RM or “soft edge”). Magnums with the needles arranged in a slight arc, which conforms better to the curvature of the skin and produces softer edges. Widely used for realistic shading and smooth colour blending.

The choice of needle configuration is a technical decision that the artist makes based on the style and the specific passage of the tattoo being worked on. A single tattoo may use several different configurations — a round liner for the outline, a round shader for detail shading, and a magnum for large fills.

In machine tattooing, the needle is driven into the skin mechanically — powered by a device that converts electrical energy into the rapid up-and-down motion of the needle.

Coil machines

Coil machines are an older technology, in use since the late nineteenth century. A coil machine uses a pair of electromagnetic coils to create a magnetic field that pulls a metal armature bar downward. The armature bar is connected to the needle bar, so when the armature moves down, the needle moves down into the skin. When the circuit breaks (because the armature bar’s movement disconnects a contact point), the magnetic field collapses, a spring pulls the armature back up, the contact reconnects, and the cycle repeats. This produces a rapid reciprocating motion — the characteristic buzzing of a coil machine. Depending on the setup, a coil machine typically drives the needle at a rate of roughly 50 to 150 cycles per second.

Coil machines are heavy, loud, and require careful tuning — the spring tension, the contact gap, the capacitor value, and the power supply voltage all affect the machine’s behaviour. A well-tuned coil machine in experienced hands is still a capable tool, and some artists prefer coils for specific applications (heavy line work, traditional colour packing). But in most contemporary shops, coils have been replaced by rotary machines.

Rotary machines

Rotary machines use a small electric motor to convert rotational motion into the linear up-and-down movement of the needle. The motor spins; a cam, a crank, or an eccentric mechanism converts the spin into reciprocation. Rotary machines have existed since the early twentieth century, but the form that dominates contemporary tattooing — the pen-style rotary — is a development of the 2010s.

Pen machines are rotary machines built in the form factor of a thick pen or marker. The motor, the drive mechanism, and the needle attachment are all housed in a single cylindrical body that the artist holds and manoeuvres like a writing instrument. This is a significant ergonomic change from coil machines, which are held more like a tool or a small power drill and produce substantial vibration in the hand.

Pen machines use cartridge needles — pre-assembled, pre-sterilised, disposable units that click or press into the machine’s grip. Each cartridge contains the needle grouping (liner, shader, magnum, or other configuration), a housing, and a built-in membrane that prevents ink from flowing back into the machine body. This membrane system is a meaningful hygiene improvement over the older tube-and-needle setup used with coil machines, where the needle bar, tube, and grip all had to be sterilised separately between clients.

The artist controls a pen machine through two main settings: voltage (which determines the motor speed and therefore the force of the needle’s stroke) and, on many models, stroke length (the distance the needle travels in each cycle). Lower voltage and shorter stroke produce a gentler, more precise action suited to fine-line work, shading, and delicate skin areas. Higher voltage and longer stroke produce a more forceful action suited to bold outlining and dense colour packing. Some machines offer adjustable stroke via a dial or interchangeable drive mechanisms; others have a fixed stroke and rely on voltage adjustment alone.

Recent pen machines have added wireless capability — a built-in rechargeable battery that eliminates the power cord entirely, giving the artist full freedom of movement. Wireless pens have become standard in many studios, particularly for artists who work at conventions or in positions where a cable is restrictive.

Pen machines are lighter, quieter, and produce less hand fatigue than coil machines. They are easier to set up (insert a cartridge and turn the machine on), easier to clean (dispose of the cartridge, wipe the body), and faster to switch between needle configurations during a session. These practical advantages, combined with the improved hygiene of the cartridge system, are why pen machines have replaced coils as the default equipment in most professional studios worldwide.

What the machine does that the hand cannot

The essential function of any tattoo machine — coil or pen — is speed and consistency. A machine drives the needle into the skin at a rate and with a regularity that no human hand could match unaided. This speed matters because tattooing is a race against the body’s inflammatory response — the longer the skin is worked, the more it swells, bleeds, and becomes difficult to tattoo cleanly. A machine allows the artist to deposit ink efficiently before the skin’s defences make further work counterproductive.

When the needle punctures the skin, several things happen simultaneously.

The wound

Each puncture creates a micro-wound — a tiny channel through the epidermis and into the dermis. The needle damages cells along its path, rupturing keratinocytes in the epidermis and disrupting collagen fibres in the dermis. Blood capillaries in the dermis are also ruptured, which is why tattooing produces bleeding.

Ink deposition

As the needle enters and exits, the ink clinging to its surface is deposited in the wound channel. Some of the ink settles in the dermis, lodging between collagen fibres and in the extracellular matrix — the structural scaffolding of the dermal tissue. Some of the ink is carried upward and remains on the skin’s surface (the excess ink that the artist wipes away during the session). Some of the ink is carried downward by gravity and by the motion of tissue fluid.

The inflammatory response

The body immediately detects the wound and the foreign material (ink). Within minutes, the area begins to swell and redden as blood vessels in the dermis dilate, increasing blood flow to the site. This is the beginning of the acute inflammatory response — the body’s first line of defence against tissue damage and foreign material.

Immune cell recruitment

The inflammatory signals attract immune cells to the wound site. The first responders are neutrophils — white blood cells that arrive within hours and begin clearing damaged tissue and bacteria. Within a day or two, macrophages arrive. Macrophages are the key players in the tattoo’s long-term fate.

Macrophages are large white blood cells whose primary function is to engulf and digest foreign particles, dead cells, and debris. When macrophages encounter tattoo ink in the dermis, they attempt to do what they are designed to do: eat it.

Some ink particles are small enough for macrophages to engulf. The macrophage surrounds the particle, internalises it, and attempts to break it down. Many tattoo pigments, however, are chemically inert — the macrophage can contain them but cannot digest them. The macrophage holds the ink particle inside itself indefinitely, sitting in the dermis with its cargo of undigested pigment. This is one of the mechanisms by which tattoo ink persists: the ink is not free-floating in the tissue but is held inside living cells that cannot destroy it.

Other ink particles are too large for any single macrophage to engulf. These particles lodge in the extracellular matrix of the dermis — trapped in the collagen network — and remain there passively.

When a macrophage eventually dies (as all cells do), it releases its contents, including the ink particles it was holding. Neighbouring macrophages then engulf the released ink and take over the job of containing it. This cycle — capture, hold, die, release, recapture — has been demonstrated in research on tattooed mice and is believed to explain why tattoos persist for decades despite the continuous turnover of the immune cells that hold the ink. The ink stays because the system that is trying to remove it keeps inadvertently preserving it.

This is also why tattoos change over time. Each cycle of macrophage death and recapture is imperfect. Some ink is lost — carried away by the lymphatic system to the nearest lymph nodes (which is why the lymph nodes nearest a tattooed area often contain traces of tattoo pigment). Some ink particles shift position slightly with each recapture. Over years and decades, the cumulative effect of these small shifts is the gradual softening and spreading of the tattoo — the loss of fine detail, the thickening of lines, and the overall diffusion that characterises an aged tattoo.

Full healing — the point at which the dermal tissue has stabilised and the tattoo is no longer actively changing — takes roughly six to eight weeks, though the remodelling phase can continue at a cellular level for several months. Most artists recommend waiting at least four to six weeks before evaluating the final appearance of a piece, and some recommend a touch-up session after this period to reinforce any areas where the ink did not hold fully.

Aftercare is not cosmetic fussing. It is wound management, and the choices made during the healing period directly affect how much ink survives in the dermis.

• Moisture. Keeping the healing tattoo appropriately moisturised helps prevent excessive scabbing. A thick scab pulls ink out of the dermis as it separates from the skin — this is one of the most common causes of patchy healing. A thin, well-moisturised healing layer minimises ink loss. Most aftercare protocols use a thin layer of unscented moisturiser or a specialised tattoo healing ointment applied several times a day during the first one to two weeks.
• Cleanliness. The tattooed skin is an open wound during the first days. Bacteria introduced to the wound can cause infection, which damages tissue and destroys ink. Gentle washing with mild, unscented soap and clean hands, followed by patting dry (not rubbing), is standard practice.
• Sun protection. Ultraviolet radiation breaks down tattoo pigments, particularly lighter colours (red, yellow, orange, and light blue are most vulnerable). Sun exposure during healing is especially damaging because the new epidermis is thinner and less protective than mature skin. Long-term sun protection — sunscreen over healed tattoos, particularly on exposed body parts — slows the fading process over the life of the tattoo.
• Avoiding mechanical damage. Picking at scabs or peeling skin pulls ink from the dermis. Tight clothing that rubs against the healing tattoo can do the same. Submerging the tattoo in water (swimming pools, baths, hot tubs) during the healing period introduces bacteria. It softens the healing scab, which increases the risk of ink loss and infection.

Understanding how tattoos work also explains how removal works. Laser tattoo removal uses targeted pulses of light energy to break large ink particles into smaller fragments. The laser’s wavelength is matched to the colour of the ink — different colours absorb different wavelengths. When a large ink particle absorbs the laser energy, it shatters into smaller pieces. These smaller fragments are now small enough for macrophages to engulf, digest, and transport away through the lymphatic system.

Removal requires multiple sessions because only a fraction of the ink is fragmented in each treatment. The body needs time between sessions to clear the fragmented particles before the next round. Complete removal can take 10 or more sessions spread over a year or longer, and some colours (particularly greens and light blues) are more resistant to laser treatment than others.

The macrophage cycle that keeps tattoos in place is the same cycle that removal disrupts. The ink stays because the particles are too big for the body to remove; the laser makes them small enough to go.