Materials & SettingsModule 4.2~3 min read

Color Annealing on Stainless / Titanium

The MOPA killer feature. By controlling pulse width, frequency, power, and speed you grow oxide layers of varying thickness, and oxide thickness controls color via thin-film interference.

The color map

Color	Oxide thickness	Energy delivery
Bronze / brown	~30 nm	low energy, fast
Purple / violet	~50 nm	↑
Blue (light → dark)	~70-90 nm	↑
Yellow / gold	~100-130 nm	↑
Pink / magenta	~150 nm	↑
Green	~200 nm	highest

Nothing is being dyed. The laser heats the surface just enough to grow a transparent oxide film, and the thickness of that film picks the color, the same way oil on water does.

Starting settings (per color, on raw 304 stainless)

Color	Speed	Power	Freq	Pulse
Light gold	800 mm/s	35%	100 kHz	200 ns
Dark blue	300 mm/s	25%	60 kHz	200 ns
Violet / purple	500 mm/s	25%	60 kHz	200 ns
Green	200 mm/s	35%	100 kHz	200 ns
Pink	700 mm/s	20%	80 kHz	200 ns

These per-color numbers are one regime (200ns, mid-frequency). Color annealing also works in a short-pulse / high-frequency regime, the same family the black recipe below uses. There is no single correct set of numbers; the parameter space is large and machine-dependent. Run the test card to find your machine's map.

Push the anneal to black

Black is the far end of this same oxide-growth spectrum, not a separate trick. You can dial the anneal all the way to a dense, focused black that lives in the same visual family as your annealed colors, ideal when you want a multi-color piece with matching black accents. Community-reported recipe on a 60W JPT MOPA with a 210mm lens, beam in focus:

Speed	500 mm/s
Power	20%
Frequency	325 kHz
Q-pulse	20 ns
Line interval	0.002 mm
Hatch	Bi-directional, crosshatch

Note how this differs from the per-color settings: very high frequency, short pulse, slow speed, very tight interval. This is a focused, annealed black. It is a different route than the defocused short-pulse (1-4ns) black, both grow an oxide layer, but the focused-anneal recipe keeps the surface texture consistent with your annealed colors, while the defocused method is a standalone deep-black approach. Use the annealed-black recipe for color-plus-black pieces; use either for a standalone black mark.

Annealing is forgiving of large lenses

Unlike deep engraving (where you want the tightest lens for maximum power density), color and black annealing depend on controlled, modest heat input, not peak power. Large lenses anneal cleanly: the recipe above runs on a 210mm lens with no issue. Use whatever lens covers your part; you are not sacrificing color quality by going big.

The test card you should run today

10×10 grid: rows = speed (200-2000 in 200 increments), cols = power (10-50 in 5% increments).
Fix freq at 80 kHz, pulse at 200 ns first run.
Hatch interval 0.04 mm, single pass.
Run, photograph under daylight, label every cell. Reference card lives next to the laser.
Re-run grid varying frequency on a second card to fill in the color map.

Tip

Surface prep matters more here than anywhere else. Wipe with isopropyl alcohol, fingerprint oil ruins color. Brushed stainless gives a directional sheen under color; mirror-polished gives the deepest, most saturated colors but every scratch shows.

Titanium notes

Titanium colors more easily than stainless and runs across a wider color spectrum. Drop power and pulse width compared to stainless. Watch for chromatic shifts at edges, Ti is sensitive to even small focus error.