Metamorphic Stone Laser Cleaning Materials
Technical parameters for laser cleaning of metamorphic stones including marble, slate, quartzite, schist, gneiss, and soapstone. Optimized for delicate surface preservation, pollution crust removal, and historic monument restoration.
Marble & Calcite Sensitivity
Marble (calcite-based, 3-4 Mohs) undergoes thermal decomposition at 600-800°C releasing CO₂. Laser cleaning requires fluence below 1-2 J/cm² and pulse durations under 20 ns to avoid calcination. Yellowing indicates overheating above the safe threshold.
Black Gypsum Crust Removal on Marble
Marble monuments develop black gypsum (calcium sulfate) crusts from SO₂ pollution. Laser cleaning removes these 100-500 micron crusts selectively, leaving the underlying calcite intact. Sandblasting removes 1-3 mm of material, erasing carved details.
Slate & Schist Exfoliation Risk
Foliated metamorphic stones (slate, schist, gneiss) have directional cleavage planes. Laser cleaning along the foliation direction causes 0.5-2 mm flaking if fluence exceeds 2-3 J/cm². Reduce fluence by 40-60% and scan parallel to foliation.
Quartzite High Durability
Quartzite (7-8 Mohs) is highly resistant to laser damage, tolerating 3-6 J/cm² fluence. The quartz matrix reflects 1064nm efficiently, requiring higher fluence for dark crust removal. Heat dissipation is excellent due to high thermal conductivity (6-8 W/m·K).