The one split that decides everything
Before you touch a single setting, answer one question: is the metal bare or coated? That split decides your entire workflow, and it is where most beginners waste their first sheet of aluminum.
- Bare metal - raw stainless, brass, aluminum, titanium. The surface has nothing for a diode or CO2 beam to grab, so those lasers just reflect off it and leave nothing. To photo-engrave bare metal you need either a fiber laser (which the metal actually absorbs) or a marking spray that gives the beam something to bond to.
- Coated metal - anodized aluminum, painted, powder-coated, or spray-marked stock. Now the laser is working on the coating, not the steel underneath, and almost any machine can do it. This is where diode and CO2 owners get clean, detailed photos.
So the honest answer to "can my laser engrave a photo on metal?" is: on the right metal, yes. A 10 W diode will never mark a bare stainless flask, but it will burn a gallery-quality portrait onto a black-anodized aluminum tag all day.
Anodized aluminum - the easy win
If you own a diode or CO2 laser and want photos on metal, start here. Anodized aluminum is the single most forgiving metal in the hobby, and it needs no spray, no special gas and no second pass.
Anodizing puts a hard, dyed oxide layer on the aluminum. The laser doesn't cut or blacken it - it bleaches the dye away, exposing the pale silver oxide underneath. Because a light mark appears where the beam hits, anodized aluminum is a light-marking material, exactly like slate or glass.
Invert the image
This is the step people forget. Since the laser makes the light tones, you must invert the photo before engraving - burn the highlights, leave the shadows as the original dark anodized colour. Skip it and you get a photographic negative: dark hair goes white, bright cheeks go black. Black-anodized stock gives the strongest contrast and is the classic choice for portraits and pet memorials.
Why it holds detail so well
The oxide layer is thin and uniform, so the laser bleaches it cleanly at low power without melting or spreading. That means the dots stay crisp and you can push DPI higher than on wood - fine facial detail survives that would smear on a grainy pine plaque.
Marking spray on bare metal (Cermark & co.)
If you have a diode or CO2 laser but the part is bare metal - a stainless tumbler, a brass plate, a raw aluminum dog tag - a marking spray is how you get a permanent mark. The best-known is Cermark; Thermark is the same idea, and hobbyists often use dry-moly lube (molybdenum disulfide, sold as an engine assembly spray) as a cheap stand-in.
These products are a suspension of metal-oxide particles. You spray a thin, even coat on the bare metal, let it dry, then engrave. The laser's heat fuses the particles into the surface, leaving a hard black bonded mark. Everything the beam missed wipes off with water or isopropyl alcohol, leaving a permanent, dishwasher-safe black image.
The workflow
- Clean the metal. Any oil or fingerprint stops the coating bonding. Wipe with isopropyl alcohol first.
- Coat thin and even. A light, uniform grey haze marks better than a thick coat - too much spray absorbs the heat and gives a weak, patchy mark. Let it dry fully.
- Engrave slower, not hotter. Marking spray needs sustained heat to bond. On a diode you typically run low power, low speed so the beam dwells long enough to fuse the coating.
- Wash off the residue. Scrub away the unmarked spray under water. What is left is the bonded black image.
Because this is a dark-marking process - black mark on shiny metal - you do not invert the image. Burn the shadows as normal, like you would on wood.
Stainless steel: annealing vs spray
Stainless is the metal people most want to personalise - flasks, knives, tools, jewellery - and it has two completely different photo routes depending on your laser.
Fiber annealing (no spray)
A fiber laser can mark stainless directly by annealing: instead of removing material, it heats the steel just enough to grow a thin oxide layer that shows as a colour - typically deep black or brown - without breaking the surface. The result is smooth, corrosion-safe and permanent, which is why fiber-annealed stainless is the gold standard for photo tags and medical parts. Annealing runs at high power, low speed, slightly defocused, so heat spreads and the oxide builds evenly.
Marking spray (diode / CO2)
Without a fiber laser, you fall back to the Cermark route above: coat the stainless, engrave with a diode or CO2, wash off. This gives a genuinely permanent black mark and is how most hobbyists put photos on a stainless tumbler. It is dark-marking, so no invert.
| Laser | Method | Spray? | Mark colour |
|---|---|---|---|
| Fiber | Annealing | No | Black / brown oxide |
| Diode / CO2 | Marking spray | Yes (Cermark etc.) | Bonded black |
Both are dark-marking - burn the photo positive. Only anodized aluminum needs the invert.
Coated, painted and powder-coated metal
The forgotten third category. Any metal that already carries a coloured layer - powder-coated tumblers, painted signs, coated business-card stock - can be photo-engraved by ablating the coating to reveal the metal beneath. A diode or CO2 laser removes the paint or powder where it fires, and the bright metal shows through.
This is light-marking like anodized aluminum: the mark is the exposed bright metal, the background is the dark coating. Invert the image so the laser removes coating in the highlights and leaves it in the shadows.
- Powder-coated stainless tumblers are a huge seller - the laser lifts the powder to a bright silver photo. Run low power so you clear the coat without gouging the metal.
- Painted or coated aluminum signage behaves the same way; test on a corner because coat thickness varies wildly between suppliers.
Image prep: dither, DPI and contrast
The prep is the same for every metal path, and it is where a good file beats a good machine. Metal is smooth and reflective, which is a gift: it holds fine dots better than any wood, so you can chase real photographic detail.
Dither or grayscale?
Dither, in almost every case. Metal surfaces don't hold reliable graytones from a diode's power scaling, so on/off halftone dots give the most faithful result. Because metal is so smooth, use the finer algorithm:
| Surface | Dither | Why |
|---|---|---|
| Anodized aluminum | Floyd–Steinberg | Smooth, clean bleach holds a tight, fine grain |
| Marking spray on steel | Floyd–Steinberg / Jarvis | Fine if the coat is even; Jarvis if dots merge |
| Fiber annealed steel | Grayscale or fine dither | Fiber holds true grays, so power-scaled tone can work |
Flip between algorithms and preview the result in the free Dithering Lab, or read the full breakdown in best dithering settings for laser engraving.
DPI
Metal takes higher DPI than wood because the mark is crisp and doesn't bleed. A 10 W diode on anodized aluminum handles 300–381 DPI (0.067–0.085 mm interval); a fiber or CO2 can push higher. As always, higher is not automatically better - if the image goes muddy, drop the DPI before you touch power. The Laser Calculator converts DPI, interval, size and time for you.
Contrast and inversion
Boost contrast until the photo looks slightly too punchy on screen - the dither spreads tone back out. Then remember the invert rule: light-marking metals (anodized, coated) get inverted; dark-marking metals (spray, fiber anneal) stay positive. Cut a busy background first with the Background Remover so the subject keeps the full tonal range.
Prep your metal photo now - free, in your browser
Starting settings by material
These are starting points, not guarantees. Every machine, lens, batch of stock and can of spray is different, so treat these as the centre square of a test grid - burn the grid, pick the best square, use those numbers. Never run a full piece on numbers from a web page.
Anodized aluminum (light-marking, invert)
| Laser | Power | Speed | DPI |
|---|---|---|---|
| 5–10 W diode | 25–40% | 150–250 mm/s | 300–381 |
| 20 W diode | 15–30% | 250–350 mm/s | 318–381 |
| 40–60 W CO2 | 12–20% | 300–500 mm/s | 333–500 |
The mark is a bleach, so low power is the rule - too hot and you gouge through the oxide into raw aluminum and lose the tone.
Stainless with marking spray (dark-marking, no invert)
| Laser | Power | Speed | DPI |
|---|---|---|---|
| 5–10 W diode | 80–100% | 80–150 mm/s | 254–318 |
| 40–60 W CO2 | 15–30% | 150–300 mm/s | 300–381 |
Spray needs dwell time to bond, so run slow. If the mark wipes off with the residue, you were too fast or too cool - slow down before you add power.
Fiber annealing on stainless (dark-marking, no invert)
| Laser | Power | Speed | Notes |
|---|---|---|---|
| 20–30 W fiber | 60–80% | 200–500 mm/s | Slightly defocused, low frequency (~20–30 kHz) for a dark anneal |
Annealing lives on heat build-up, not ablation. Defocusing a millimetre or two and dropping the frequency grows a darker, smoother oxide - dial it in on scrap of the same alloy.
Ventilation and spray safety
Metal itself is inert to engrave, but two things here need real care.
- Marking sprays. Cermark, Thermark and especially dry-moly are aerosols with solvents and fine metal-oxide particles. Spray them in a ventilated area, wear a respirator or mask, and never spray near the laser's electronics. Let the coat dry fully before engraving - wet solvent plus a laser is a fire risk.
- Fumes while engraving. Ablating powder-coat, paint or bonded spray releases particulate you should not breathe. Run your fume extraction or exhaust the whole time, exactly as you would on any material.
- Reflection. Bare polished metal reflects laser light. Wear the correct laser safety glasses for your wavelength and never assume "it's only metal, it won't burn me."
Frequently asked questions
Can a diode laser engrave a photo on metal?
Not on bare metal - a diode reflects straight off raw steel or aluminum. But it engraves photos beautifully on anodized aluminum (bleaching the dye, no spray needed) and on bare metal coated with a marking spray like Cermark or dry-moly.
Do I need to invert the image for anodized aluminum?
Yes. Anodized aluminum is light-marking - the laser bleaches the dye to pale silver. Invert the photo so the laser burns the highlights and leaves the shadows as the original dark colour. Marking spray and fiber annealing are dark-marking, so those stay positive.
What is Cermark and do I need it for stainless steel?
Cermark (and equivalents like Thermark or dry-moly lube) is a spray that fuses to bare metal under laser heat, leaving a permanent bonded black mark. A diode or CO2 can't mark bare stainless alone, so you coat, engrave, then wash off the residue. A fiber laser anneals stainless directly with no spray.
Which metal is easiest for laser photo engraving?
Anodized aluminum, by a mile. No spray, single pass on almost any diode or CO2, and it holds fine detail. Black-anodized blanks give the strongest contrast for portraits and pet memorials.
Keep going
New to the whole workflow? Start with converting a photo into a laser-ready file, then dial in your dithering settings. Comparing materials? See wood, acrylic, leather and slate - or browse community numbers in the Settings DB.