Stone, Slate & Marble

CO2 marks stone via thermal stress, the heated layer fractures into a fine white powder that contrasts with the dark substrate. Different stones behave very differently under the beam.

Slate: the easiest stone

Slate is metamorphic shale. Naturally fractures into clean layers. Takes laser engraving better than any other stone, instant white-on-black mark with no special prep.

• Settings: 300 mm/s, 25-35% power, line interval 0.08 mm, single pass. Air assist minimum, just enough flow to keep dust off the lens. Never fully off.
• Image mode: Stucki for photos, Threshold for line art, Grayscale for tonal relief.
• Outdoor durability: excellent. Engraving doesn't fade in sun or rain.
• Sources: craft suppliers, kitchen-supply (cheese boards), tile suppliers.

Marble: fragile, beautiful

Marble is calcium carbonate. Softer than slate; cracks more easily. Engrave marks appear as lighter areas where the surface has been ablated, creating a "frosted" look on dark/colored marble or a darker tonal shift on light marble.

• Settings: 400 mm/s, 18-25% power, line interval 0.08 mm. Multi-pass at lower power. Never single-pass aggressive.
• Watch for: cracking. If marble cracks during engraving. Drop power 5%, slow speed, add another pass.
• Light marble (Carrara, white): contrast is subtle. Best for shaded gradient designs, not high-contrast text.
• Dark marble (Nero Marquina, dark green): better contrast; closer to slate behavior.
• Outdoor durability: good. Avoid acidic cleaners.

Granite: challenging

Igneous rock with quartz / feldspar / mica. Reflective minerals make laser engraving uneven. Best on dark, fine-grained granite (absolute black, dark green).

• Settings: 300 mm/s, 30-40% power, line interval 0.08 mm.
• Caveat: coarse-grained granite (with visible feldspar crystals) gives speckled, inconsistent engraving. Test the specific stone before quoting customer work.
• White on black (paint-fill option): engrave, then rub white acrylic paint into the recess, wipe high points. Maximum contrast.

Limestone: case-by-case

Sedimentary, similar to marble in engraving behavior. Often cheaper. Test a sample before committing to a project, limestone composition varies wildly by quarry.

Travertine: porous. Watch for inconsistency

Hole-pocked sedimentary stone. Engraving fills holes with debris and looks dirty. If you must engrave travertine, fill holes with epoxy first, sand smooth, then engrave.

Common stone applications

• Slate cheese boards: names, dates, monograms. $25-65 retail.
• Memorial stones / pet markers: high emotional value, low price sensitivity. $50-150.
• House-number signs: slate or granite, outdoor-rated. $35-90.
• Wedding venue signs: large slate slabs, custom monograms. $80-250.
• Coasters: slate cut into 4×4" squares; sets of 4-6. $25-70/set.
• Engraved marble plaques: premium award/memorial work. $80-200.

Pre-engrave prep

• Wipe with isopropyl to remove dust and oils.
• For dark stones: no masking required.
• For light stones (white marble, light granite): mask with painter's tape to catch smoke residue. Peel after.
• For optimal contrast on engraved areas: brush with a stiff nylon brush after engraving to clear loose powder.

Post-finishing

• Sealant: outdoor stones benefit from a sealer (Tenax, AquaMix). Apply after engraving, not before.
• Color enhancement: rub graphite, white acrylic paint, or ink into engraved recesses for deeper contrast. Wipe high points clean.
• Protective wax: Renaissance Wax for indoor display pieces.