Stage 1: Pick your mark

What marks can your laser actually make?

"Mark aluminum" can mean five different things. A dark mark. A frosted white one. A bright reflective one. A color. A deep engrave you can feel. Each is a physically different process happening on the surface, and your laser can only do some of them.

This is the map. Find your material, find your laser, and see which marks are on the table and why. No borrowed settings, no guessing at what's possible.

The marks

Dark

A dark mark: smoky gray, charcoal, or black. The workhorse for logos, text, and serials.

Gray etch

A softer gray. Lighter contrast than a dark mark, often smoother and faster to run.

Frosted white

Matte, satin white. Looks the same from every angle. Think the back of a MacBook, or frosted glass.

Bright / polished

Mirror-bright. Flashes when it catches the light, fades from the wrong angle. Angle-dependent by nature.

Color

Oxide colors like gold, bronze, blue, purple, and rainbow. A thin transparent film bending light, tuned by heat.

Deep engrave

Real depth you can feel with a fingernail. Survives abrasion. Costs passes and time.

Cut through

Fully severs the material.

The full chart

Each cell shows the marks that material can take from that laser. An empty cell means the physics is against you. The light bounces off, passes through, or the material can't hold the mark. Material names in dotted underline have a full breakdown below.

Material	Diode 450 nm	CO₂ 10,600 nm	Fiber 1,064 nm	Fiber MOPA 1,064 nm	UV 355 nm
Bare metals
Bare aluminum	Not really	Not really	DarkGray etchFrosted whiteBright / polishedDeep engrave	DarkGray etchFrosted whiteBright / polishedDeep engrave	Frosted whiteGray etch
Stainless steel	Not really	Not really	DarkGray etchFrosted whiteDeep engrave	ColorDarkGray etchFrosted whiteDeep engrave	ColorFrosted whiteGray etch
Mild / carbon steel	Not really	Not really	DarkGray etchDeep engrave	DarkGray etchFrosted whiteDeep engrave	DarkFrosted white
Brass & copper	Not really	Not really	DarkGray etchDeep engrave	DarkGray etchFrosted whiteDeep engrave	Frosted whiteGray etch
Titanium	Not really	Not really	DarkGray etchDeep engrave	ColorDarkGray etchFrosted whiteDeep engrave	ColorDarkFrosted white
Coated metals
Anodized aluminum	Bright / polished	Bright / polished	Bright / polishedDark	Bright / polishedDarkColor	Bright / polishedColor
Powder-coated / painted metal	Bright / polished	Bright / polished	Bright / polishedDark	Bright / polishedDark	Bright / polished
Coated tumblers / drinkware	Bright / polished	Bright / polished	Bright / polishedDark	Bright / polishedDark	Bright / polished
Plastics & acrylic
Cast acrylic	Not really	Frosted whiteDeep engraveCut through	Not really	Not really	Frosted whiteGray etchCut through
Extruded acrylic	Not really	Gray etchDeep engraveCut through	Not really	Not really	Gray etch
ABS & most plastics	DarkFrosted white	DarkFrosted whiteCut through	DarkFrosted white	DarkFrosted white	DarkFrosted white
Wood & organics
Wood & plywood	Gray etchDarkDeep engraveCut through	Gray etchDarkDeep engraveCut through	Not really	Not really	Gray etchDarkCut through
Leather	DarkDeep engraveCut through	Gray etchDarkDeep engraveCut through	Not really	Not really	Gray etchDark
Paper & cardboard	Gray etchCut through	Gray etchDarkCut through	Not really	Not really	Gray etchCut through
Glass & stone
Glass	Frosted white	Frosted white	Not really	Not really	Frosted white
Slate & stone	Frosted white	Frosted white	Frosted white	Frosted white	Frosted white

What the five laser types are▾

Diode (450 nm)

Blue light. Common, affordable, gantry. Great on wood. Bounces off bare metal and passes straight through clear acrylic.

CO₂ (10,600 nm)

Infrared. The organics workhorse for wood, acrylic, leather, and glass. Reflects off bare metal, so it needs a marking spray there.

Fiber (1,064 nm)

Standard fiber. Built for bare metal marking and engraving. No pulse-width control, so no color.

Fiber MOPA (1,064 nm)

Fiber with a tunable pulse width. Everything standard fiber does, plus oxide colors on steel and finer control.

UV (355 nm)

Cold light. Marks almost anything with very little heat: glass, plastics, coated metals. Expensive, and usually low power.

Material breakdowns

The full story on each material: what each mark really is, what's physically happening, and the honest limits. The stuff no settings chart tells you.

Jump to:Bare aluminum Stainless steel Anodized aluminum Cast acrylic Wood & plywood

Bare aluminum

Reflects about 91% of fiber light, so every mark is a surface texture. That is why they all shift with viewing angle, and why it never goes truly black.

Bare aluminum is one of the trickiest metals to mark, and it is worth understanding why before you burn anything. Polished aluminum reflects about 91% of a fiber laser's light, so your beam mostly bounces off. Every mark below works by changing the surface so it stops bouncing light back the same way. That is the whole game. It also means every mark on bare aluminum is a texture, and textures look different depending on the angle you view them from. Keep that in mind. It explains almost everything that surprises people about this material.

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The dark mark

FiberFiber MOPA

What you see: A smoky gray to charcoal mark. The workhorse for logos, text, and serial numbers.
What's happening: The laser builds a microscopic forest of pits and ridges on the surface. Light falls in and cannot find its way back out. More passes grow the forest deeper and darker.
Honest limits: Bare aluminum never goes truly black. It tops out at a dark gray, and that is physics, not your machine. Steel and titanium go black by growing a colored oxide film, and aluminum's oxide does not play that game. Push the power too hard trying to force it and you make things worse: the surface melts and smooths itself back out, erasing the texture you just built. Darker on aluminum comes from stacking gentle hits, not from one big one.

The frosted white mark

FiberFiber MOPAUV

What you see: A soft, matte, silvery-white mark. Looks the same from every angle. Think the back of a MacBook.
What's happening: A much shallower version of the same texture trick. The laser lightly roughens the surface so light scatters softly in every direction instead of glinting.
Honest limits: It is not a bright white like paint. It is a satin frost. But it is the most dependable mark on this list: even, angle-stable, and fast to run.

The bright polished mark

FiberFiber MOPA

What you see: A mirror-bright mark that flashes when it catches the light. Gorgeous head-on, nearly invisible from the wrong angle.
What's happening: The opposite of the other two. The laser melts a thin layer and surface tension pulls it flat as it refreezes, like still water turning to ice. You have made a tiny mirror.
Honest limits: The angle-shifting is not a flaw you can tune out. A mirror is angle-dependent by definition. If you want a white mark that reads the same from everywhere, you want the frosted one. Pick this when the piece will be viewed head-on and you want it to pop.

The deep engrave

FiberFiber MOPA

What you see: A mark with real depth. You can feel it with a fingernail. Survives abrasion and paint fill.
What's happening: Straight material removal. The laser vaporizes metal, layer by layer, over many passes.
Honest limits: Depth costs time. Real depth takes ten or twenty passes, not two. And the bottom of a deep engrave has its own finish, usually a rough gray, so if you want deep AND dark, that is two recipes stacked.

What it can't do

True black, and steel-style rainbow colors. Both come from oxide-film chemistry that aluminum does not have. If someone shows you jet black on 'aluminum,' it is almost always anodized aluminum, which is a different material as far as the laser is concerned, where the coating does the darkening.

Choosing your laser

Bare aluminum mostly ignores diode and CO₂ lasers. The reflectivity that makes fiber marking tricky makes diode and CO₂ marking nearly impossible. You will get a faint smudge at best. If you have a diode or CO₂ and need to mark aluminum, use anodized stock or a marking spray.

Stainless steel

The richest metal for marks. Grows real oxide-interference colors, goes genuinely black by annealing, and takes a deep engrave, all with no coating.

If aluminum is the frustrating metal, stainless is the generous one. It does everything aluminum cannot. The reason is chemistry: stainless has chromium in it, and chromium loves oxygen. Heat the surface with a laser and it grows a thin, clear oxide film, and the thickness of that film is something you can dial with heat. Thin films bend light into colors. Thicker films go black. None of it removes metal, so the part stays smooth and rust-resistant. This is the exact trick TRUMPF says works on steel and titanium but not aluminum, which is why stainless can hit a full rainbow and true black while bare aluminum tops out at gray.

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The oxide rainbow

Fiber MOPA

What you see: Real color with no paint: gold, bronze, red, purple, blue, teal, green, all the way to a rainbow. The color shifts a little as you tilt it, because it is made of light, not pigment.
What's happening: Same physics as an oil slick or a soap bubble. The laser grows a paper-thin transparent oxide film, and light bouncing off the top and the bottom of that film interferes to make a color. Film thickness picks the color. Thickness is set by how much heat lands per spot, and the main knob for that is speed: slower means more heat means the color marches from gold toward blue toward green toward black.
Honest limits: This is a MOPA specialty. It needs the tunable pulse width that only MOPA has, and the exact numbers do not copy cleanly between machines because color really tracks pulses-per-area, a value each machine reaches differently. A realistic production palette is roughly eight to ten reliable colors, not an infinite spectrum. And the color is heat-made, so reheating the part above about 200°C can fade it.

The black anneal

FiberFiber MOPA

What you see: A flat, matte-to-satin black. No depth you can feel, and the part stays corrosion-resistant. This is the black used on medical and food-grade tools.
What's happening: The same oxide trick as the colors, pushed further. A thick enough oxide film stops reflecting any single color and just absorbs light across the board, so it reads black. No metal is removed.
Honest limits: Black is the slowest mark to lay down, because it needs the most heat per spot. Push past the sweet spot and you stop growing oxide and start melting the surface, which gives a rougher, blotchier black that is no longer smooth or corrosion-safe. Standard fiber can do a solid black anneal too, it just cannot do the controlled colors the way MOPA can.

The frosted white / etch

FiberFiber MOPA

What you see: A pale, matte, light-gray-to-white mark. Good for a softer look or a light background.
What's happening: A different mechanism from the colors. Instead of growing a smooth film, the laser lightly roughens the surface so it scatters all light evenly, like ground glass. That reads as pale and matte.
Honest limits: Lower contrast than a black anneal, and like every stainless mark it shifts a little with viewing angle. It is a surface texture, so it is less durable than a grown-oxide color or black.

The deep engrave

FiberFiber MOPA

What you see: A tactile recess you can read by touch. For serial numbers and parts that get handled hard.
What's happening: This one does remove metal. The laser vaporizes and ejects material over many passes to cut a real groove.
Honest limits: Depth costs passes and time (twenty-plus passes for real depth). And a groove gives up the clean, corrosion-safe surface a flat anneal keeps, so for food-contact or medical parts a black anneal is often specified instead of an engrave.

What it can't do

Perfectly repeatable color across different machines. Because color tracks pulses-per-area, a gold recipe from one MOPA will not land as gold on another without re-tuning. Colors are also heat-reversible above about 200°C, and they read best in daylight rather than under narrow-spectrum LED light.

Choosing your laser

CO₂ and blue diode do almost nothing to bare stainless. CO₂ light reflects off it, and a diode's spot is too spread out to reach the oxide-color heat, so both effectively need a marking spray like Cermark to leave a legible black. That is a coating on top, not the stainless-oxide magic above. UV can make colors and fine white marks by a different route, but at low power, so it is a precision tool, not a fast or deep one.

Anodized aluminum

A hard dyed oxide skin over aluminum. Marks beautifully where bare aluminum fights you. Most lasers strip it to bright metal, and MOPA can fracture underneath for a durable black.

Anodized aluminum is a completely different animal from bare aluminum, even though the metal underneath is the same. Anodizing grows a hard, slightly porous oxide skin on the surface, then dyes and seals it. That skin absorbs laser light well, which is exactly what bare aluminum refuses to do. So the thing that makes bare aluminum hard, its mirror-like reflectivity, is hidden under a coating that marks easily. Almost every mark here is really about that coating: taking it away, or changing it, rather than touching the metal.

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The coating-strip mark (bright silver)

DiodeCO₂FiberFiber MOPAUV

What you see: A bright, high-contrast reveal: shiny bare aluminum showing through the anodized color. This is the classic engraved-anodized look, like the text on a laptop or a dog tag.
What's happening: The laser burns or vaporizes the thin colored coating away, exposing the bright metal underneath. You are basically removing paint, not marking the aluminum.
Honest limits: It only goes as deep as the coating, so there is no depth to it. And it removes the anodizing's corrosion protection exactly where you marked. Thin, cheap anodizing gives weaker contrast than a thick hardcoat.

The MOPA black

Fiber MOPA

What you see: A deep, even matte black that stays black from most angles. The premium look for anodized parts.
What's happening: Instead of blasting the coating off, MOPA's short pulses land in a narrow energy window that fractures the aluminum just beneath the still-intact oxide. The clear oxide stays on top and keeps protecting the mark, which is why this black is more durable and less angle-shifty than a stripped mark.
Honest limits: This is a MOPA trick. Standard fiber cannot hit that narrow window, so its 'black' comes out more of a gray. Even on MOPA, hitting the ideal window takes tuning, and results depend on the anodize thickness and seal, which you often cannot see. Two visually identical parts can take the mark differently.

Color and tone shifts

Fiber MOPAUV

What you see: Subtle gold, copper, blue, or olive shifts, or fine gray gradations, rather than a plain black-or-silver.
What's happening: Two things at once: thin-film interference in the oxide (the same soap-bubble effect as on stainless), and partial coating removal that changes how light reflects. The result depends on power, speed, and frequency together, not one single knob.
Honest limits: This is fiddly and not a clean grayscale dial. The dye burns off at a much lower temperature than the oxide melts, so the usable range is narrow (roughly twenty tonal steps at best). For photos, dithering beats trying to ramp power.

What it can't do

Real depth engraving. The coating is only a few thousandths of a millimeter thick, and once you are through it you are back to fighting bare aluminum. Photographic grayscale is also weak here, because the coating responds in steps rather than a smooth ramp. Dithering, not power ramps, gives the best tone.

Choosing your laser

This is the happy exception where almost every laser works. Diode does great on dark anodize but struggles on pale colors, because it needs the dye itself to absorb the blue light (a black dye drinks it in, a gold dye reflects it). CO₂ does clean silver removal and nothing else. UV works on any color and gives the finest detail, just slowly. Only MOPA reaches the true durable black.

Cast acrylic

The engraver's favorite plastic. Frosts bright white when engraved, and flame-polishes to a clear glossy edge when cut with CO₂.

Acrylic and a CO₂ laser are a perfect match, and it comes down to one fact: the CO₂ beam is tuned to a wavelength that acrylic drinks in completely, no matter what color the sheet is. All the energy lands in the top layer and the plastic vaporizes cleanly back into gas rather than charring like wood. That clean vaporization is why acrylic cuts glassy and engraves bright white. One thing to know up front: there are two kinds of acrylic, cast and extruded, and they behave differently under the laser (more on that below). Cast is the one you want for engraving.

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The frosted white engrave

CO₂UV

What you see: A bright, matte-white mark against the clear or colored sheet. The classic frosted-glass look used for signs and awards. On a clear sheet it also glows when the edge is lit, which is how edge-lit signs work.
What's happening: The laser removes a shallow layer and leaves the surface microscopically rough and foamy. That rough surface scatters light in every direction instead of letting it pass through, and scattered light reads as white. Same reason crushed glass or snow looks white even though it is clear.
Honest limits: Cast acrylic frosts brighter and more evenly than extruded. Once it is frosted it is permanent, there is no laser pass that polishes it back to clear.

The flame-polished cut edge

CO₂

What you see: A cut edge on clear acrylic that comes out smooth and glossy, almost like it was fire-polished by hand. This is acrylic's party trick and the reason it dominates laser signage.
What's happening: As the beam cuts, a thin film of melted acrylic on the edge flows back over itself and refreezes clear before the beam moves on, leaving an optically smooth wall.
Honest limits: The air assist has to be dialed just right. Too much air ripples the melt into a frosted edge, too little lets smoke into the cut. Cast acrylic gives the cleaner edge, and thick sheet (past about 10 to 15 mm) starts to crack from thermal stress and needs multiple passes.

Deep engrave & relief

CO₂

What you see: A deep pocket or a multi-level 3D relief, well beyond a surface mark. Used for stamps, molds, and dimensional signage.
What's happening: The same clean vaporization, just more of it. Slower speed digs deeper, more power gets there faster, and multiple passes at higher speed give better depth control than one slow crawl.
Honest limits: Deep engraves on clear acrylic can look a little cloudy compared to a cast opaque sheet. Go too slow in one pass and the melt bulges instead of clearing, so several faster passes usually beat one slow one.

What it can't do

You cannot un-frost a mark, and you cannot laser acrylic in full color (a laser only removes material, it does not add pigment; color acrylic graphics come from UV printing, with the laser doing the cutting). And settings never transfer between cast and extruded acrylic, or reliably between brands and thicknesses, so always test on scrap.

Choosing your laser

Here is the big one: clear acrylic is nearly invisible to a blue diode. The blue light passes straight through like a flashlight through a window (only about 8% is absorbed), so a diode does nothing to clear stock no matter how much power you throw at it. A coat of paint or masking tape gives it something to grab, but that is a workaround, not a fix. Diodes do cut dark and black acrylic, though the edge comes out rough and bubbly rather than polished. Fiber and MOPA pass straight through clear acrylic too, and only mark dark pigmented sheets. UV cuts and frosts beautifully with no yellowing, just slowly and at low power.

Safety

Two plastics look almost exactly like acrylic and are dangerous to laser. Polycarbonate (often sold as Lexan) melts, yellows, and can catch fire instead of cutting clean. PVC or vinyl mislabeled as 'clear plastic' releases chlorine gas that corrodes your machine and is genuinely hazardous to breathe. If you are not certain a clear sheet is acrylic, do not run it. A quick scrap flame test tells you: real acrylic burns clean, these do not.

Wood & plywood

A tone ladder from light toast to deep char, which is exactly why photo-realistic engraving works on wood. Grain and moisture make every board a little different.

Wood is the friendliest material on this whole list, and it comes down to one thing: heat browns wood gradually. It is not an on-or-off switch. A little heat toasts it tan, more turns it brown, more still burns it black. Because that is a smooth ramp of real shades and not a single threshold, wood can hold a photograph, which bare aluminum simply cannot. The catch is the flip side of what makes wood great: it is a natural material. Grain, moisture, and species all change the result, so wood needs testing on scrap more than almost anything else here.

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The tone ladder: toast, brown, and photo engraving

CO₂DiodeUV

What you see: Anything from a pale tan surface tint through warm brown, with the grain showing through. This continuous range is what lets you engrave a photograph or a shaded logo, not just line art.
What's happening: The laser heat rearranges the wood's own chemistry into new brown compounds, a bit more brown for a bit more heat. Because it climbs smoothly instead of flipping on, you get true shades of tone.
Honest limits: CO₂ gives the smoothest, most controllable ramp. A diode tends to jump from barely-marked straight to charred with a narrow brown middle, so diode photos lean on dithering (lots of tiny dots) rather than true shading. And the grain fights you: the hard and soft bands in a board take the beam differently, so the same settings darken unevenly across the rings. Wetter wood also comes out lighter than dry wood at the same settings.

Dark char

CO₂Diode

What you see: A near-black, burnt, slightly textured mark. High contrast, the bottom of the tone ladder.
What's happening: Push the heat higher and the surface carbonizes to black. A diode is actually good at this, since its light is absorbed best once a little char has formed.
Honest limits: Easy to overdo into scorching, raised grain, and warping on thin stock. Dark woods like walnut reach a rich dark faster than pale woods like maple or basswood.

Deep engrave & relief

CO₂

What you see: Carved depth and multi-level relief, for stamps, signage, and dimensional work.
What's happening: The same burning, just more of it, pass after pass, to remove real material.
Honest limits: Costs passes and time, and CO₂ is far more efficient at it than a diode. Deep cuts char the walls, so a deep-and-clean look often means a cleanup pass.

Cut through

CO₂DiodeUV

What you see: A clean separating cut with a thin kerf and light-to-medium char on the edge.
What's happening: A full-depth burn straight through the board.
Honest limits: CO₂ cuts thick stock in one or a few passes. A diode needs many passes and chars the edge more. UV cuts the cleanest but slowly and only on thin stock. Wet wood cuts slower and smokier.

What it can't do

Color. Wood only does tan through black, because the mark is browned wood, not pigment. And it cannot give you a recipe that transfers cleanly from board to board. Grain, moisture, and species all shift the result, which is the whole reason wood rewards a quick test on your actual stock.

Choosing your laser

CO₂ is the reference tool for wood and works the same on every species and color. A diode is popular and genuinely good here, especially on dark woods and dithered photos, just slower and more prone to charring. Fiber and MOPA are the wrong tool: their light does not couple to wood, so you get uncontrolled scorching at best. UV is clean and precise but low-power and slow.

Safety

MDF and plywood are bonded with glues that release formaldehyde when burned, so run good filtered extraction. Never laser pressure-treated lumber (it can release arsenic and chromium) or unknown painted or laminate-faced boards. Oily exotics like cocobolo and pitch-heavy softwoods can flare up at resin pockets. And never leave a running wood job unattended, because wood catches fire.

This is Stage 1. Next comes finding your settings.

Picking your mark is where the Test Lab starts. Getting the exact settings for your machine, dialed in and saved for good, is what the next four stages do. They walk you through finding, tuning, and confirming the recipe for the mark you chose here.