1 · Slate works in reverse

On wood, the laser darkens what it touches. On slate it does the opposite: the beam vaporizes the dark surface layer and leaves a pale gray mark. That means the brightest parts of your photo are the parts the laser must burn - so the image has to be inverted before engraving. Skip this step and you get a negative: dark faces, glowing backgrounds.

Rule of thumb: wood = burn the shadows, slate = burn the highlights. The same applies to glass and anodized aluminum.

2 · Contrast is everything

Slate has a narrow tonal range - roughly "dark stone" to "light gray". A photo with soft midtones turns to mud. Push contrast to about 1.4×, lift gamma slightly above 1.0 so midtones lean bright, and crop tight on the subject. Faces and pets work beautifully; busy backgrounds do not.

3 · Use Jarvis dithering at ~318 DPI

Floyd–Steinberg is the classic, but on slate its fine grain tends to close up. Jarvis spreads the error wider, producing slightly chunkier dots that stay open on stone. 318 DPI (0.08 mm interval) suits most 10 W diodes; drop to 254 DPI if your dots merge.

4 · Starting settings

For a 10 W diode (e.g. xTool D1 Pro): 150 mm/s @ 70%, one pass, image mode pass-through. For 60 W CO2: 400 mm/s @ 25%. Wipe the coaster with a damp cloth after burning - the mark turns brighter. A light coat of mineral oil afterwards deepens the background and doubles the contrast.

Every slate batch differs. Burn a small test grid on the back of one coaster first - it takes two minutes and saves the front. Generate a test grid →

5 · Let the tool do steps 1–3

The free Dithering Lab has a slate preset that inverts the image, sets gamma, contrast, Jarvis and 318 DPI in one click - then shows a burn preview on simulated stone before you commit. Your photo never leaves the browser.

Open Dithering Lab with slate preset

Gear used in this guide

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Slate coaster blanks → Food-grade mineral oil → xTool D1 Pro →