Material · stone

Laser engraving settings for slate

A laser does not cut slate — it changes the top of the stone and leaves a pale mark on the dark surface. Here are the maker-published starting points, the LaserGRBL numbers decoded, and how to get an even tone.

Safety first

Before you start Usually fine

  • Slate engraves; it is not a material a hobby laser cuts. Stone sits in the “engrave” column for diode and CO2 lasers in our diode vs CO2 vs fiber matrix, and sources disagree about fiber.
  • Natural slate is not on the university and maker do-not-cut lists we track (what not to laser cut). Painted, printed or sealed slate is a different material: if you cannot find out what the coating is, do not laser it.
  • Engraving stone releases dust and fine particles; Thunder Laser recommends exhaust and filtration. Keep your extraction running (exhaust fan calculator).
  • Open-frame machines are Class 4: wear goggles rated for your wavelength (safety glasses checker).
Moving cross-section

What the beam does

Switch the material or laser and watch the same beam give a different result.

Blue diode ≈ 450 nm
  • Slate (natural stone)
  • Pale engraved surface

The beam turns the dark top layer pale grey. Nothing is cut away deeply; the contrast comes from colour, not depth.

Cross-section, not to scale.

Laser types

Which laser can process it

These are this material’s rows from our diode vs CO2 vs fiber matrix. (full matrix)

Blue diodeEngraves only
CO2Engraves only
FiberSources disagree

Two sources say it engraves stone; xTool says its small infrared module is not suited.

Maker values

Maker settings on one scale

Every value is a starting point published by the maker, and the maker is the source; none of them were tested by us. Machines differ in optical power, so power % and speed are converted to the energy the beam puts into each millimetre of line (J/mm). Tap a point or a table row to see the original row, the math and a link that fills in the converter.

J/mm = optical W × power % × passes ÷ speed (mm/s) · J/mm² = J/mm ÷ line interval (mm)

This is the same formula as the converter. Between lasers of the same type, similar J/mm gives a similar burn. Cutting energy rises steeply with thickness, so compare rows of similar thickness.

AtomStack’s tables have no slate row. The closest is “Rock”, which does not say which stone, so treat these as the maker’s stone starting points rather than slate-tested values. Every row is engraving. LightBurn rows give power in %; LaserGRBL rows give an S-value (S700 = 70 % when S-max is 1000) and “Quality” in lines per mm (10 = 0.1 mm).

0.0010.010.11125102050100Optical power (W, log scale)J/mm (log scale)0.0010.010.11125102050100Optical power (W, log scale)J/mm (log scale)
▬ Half of Engrave rows: 0.0461–0.134 J/mmEngraveDiodeCO2IR 1,064 nmA40 Pro V2 is calculated at 48 W (the table does not say whether it is the 48 W or the 24 W setting).
22 rows
Machine (optical W)SoftwareMaker label · thicknessJobSpeed mm/minPowerIntervalPassesJ/mm
LightBurnRockEngrave5,00070%0.110.084Convert →
LaserGRBLRockEngrave5,000S7000.110.084Convert →
LightBurnRockEngrave10,00080%0.0810.096Convert →
LaserGRBLRockEngrave10,000S6000.083310.072Convert →
LightBurnRockEngrave25,00080%0.110.0461Convert →
LaserGRBLRockEngrave25,000S8000.110.0461Convert →
LightBurnRockEngrave25,00080%0.110.0461Convert →
LaserGRBLRockEngrave25,000S8000.110.0461Convert →
LightBurnRockEngrave10,00070%0.110.202Convert →
LaserGRBLRockEngrave10,00070%0.110.202Convert →
LightBurnRockEngrave10,00060%0.0810.252Convert →
LaserGRBLRockEngrave10,000S6000.083310.252Convert →
BitmapRockEngrave18,00030%0.0510.055Convert →
Vector LineRockEngrave3,50015%—10.141Convert →
BitmapRockEngrave10,00080%0.0110.0058Convert →
Vector LineRockEngrave50070%—10.101Convert →
BitmapRockEngrave6,00080%0.0810.04Convert →
Vector LineRockEngrave1,00030%—10.09Convert →
BitmapRockEngrave15,00080%0.110.064Convert →
Vector LineRockEngrave1,00020%—10.24Convert →
BitmapRockEngrave5,00080%0.0110.0115Convert →
Vector LineRockEngrave50080%—10.115Convert →

Why slate turns pale

The laser changes the surface of the stone and leaves a light mark against the darker slate (Thunder Laser). That is why the darkest, smoothest slate gives the most contrast, and why going “deeper” does not help: once the top is pale, more energy mostly makes dust and a rougher, patchier mark.

Slate is natural stone. Two coasters from the same pack can differ in colour, flatness and how cleanly the layers split, so a setting that is perfect on one can look blotchy on the next. Photos are the hardest job; text and line art forgive much more.

LaserGRBL settings for slate, decoded

LaserGRBL does not use percentages. Power is an S-value between S-MIN (used for white pixels) and S-MAX (black pixels), and the top of the scale is your controller’s maximum: LaserGRBL notes it is 1000 on some boards and 255 on others. Check $30 in the console. AtomStack’s values (S600–S800 for Rock) assume 1000.

“Quality” in the raster import is lines per millimetre (developer’s note), so 10 means a 0.1 mm line interval and 12 means about 0.083 mm. Speed is in mm/min. To turn a LightBurn row into LaserGRBL: S-MAX = power % × $30 ÷ 100, Quality = 1 ÷ interval. The line interval & DPI calculator does the DPI side.

Prep and finish

  • Clean and dry. Wipe the slate with a damp cloth and let it dry before engraving (Thunder Laser).
  • Check it is flat. Cleft slate is not machined flat. Focus on the face you are engraving, and on large pieces check the focus at more than one corner.
  • Oil — before or after. Owners disagree: some wipe on a little mineral oil first, others oil only the finished piece to even out a blotchy result (LightBurn forum). Oil darkens the untouched stone either way, so test on the back.
  • Seal outdoor pieces. Thunder Laser suggests a clear matte or satin sealant for outdoor or much-handled pieces, tested on a small area first.

How to run a slate test

  1. Use the back of the coaster or a spare piece from the same pack.
  2. In LightBurn, open Laser Tools → Material Test and vary power on one axis and speed on the other (LightBurn). It burns the riskiest box — fastest, lowest power — first.
  3. Start the grid around the maker row for a machine like yours, scaled with the power & speed converter.
  4. Pick the box with the most even pale tone, not the deepest one. For photos, run a second test on line interval.
  5. Wipe the dust off before you judge: dust looks lighter than the mark.

FAQ

What are good laser settings for slate?
There is no single answer, but makers publish starting points. AtomStack has no slate row; its “Rock” rows engrave at about 5,000–25,000 mm/min with 60–80 % power on the diode machines and a 0.08–0.1 mm interval, which works out to roughly 0.04–0.25 J/mm per line. Scale a row from a machine like yours with the power & speed converter, then run a test grid.
What LaserGRBL settings should I use for slate?
AtomStack’s LaserGRBL “Rock” rows use S600–S800 at 5,000–25,000 mm/min with Quality 10–12 lines/mm. S-values assume a maximum of 1000, so check $30 first; if your board uses 255, multiply the percentage by 2.55 instead. Quality 10 equals a 0.1 mm interval.
Can a diode laser cut slate?
No source we use lists slate or stone as cuttable on a hobby diode or CO2 laser; both are listed as engraving it. Buy slate already cut to shape and engrave the face.
Why does my slate engraving look patchy?
Usually the stone, the focus or too much energy. Natural slate varies from piece to piece, cleft slate is not flat, and over-burning makes a rough, uneven mark. Clean and dry the slate, check focus, lower the energy until the tone is even, and try oiling the finished piece.

Sources

Sources for the laser-type verdicts

Last checked 2026-11-01 · Maker values and calculations; we did not process this material ourselves.

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