Watch for signs of damage. Lannon stone can show signs of wear and age within months, if not cared for properly. Watch for obvious discoloration, such as black streaks caused by grime. Green or yellowish lines or patches may be due to mold growth.
Excessive flaking or chipping means that the stone is absorbing too much moisture. Apply a coat of protectant. There are commercial sealing products that are made specifically for stone.
Purchase the protectant at a hardware store or by contacting a flooring professional. Some protectants require a spray on application whereas others can be brushed directly on to the stone. Follow the directions on the package carefully.
Test any cleaning products in an inconspicuous area. Before you apply any cleaner to a broad area, dab a small amount of it onto an area of the stone that is not readily visible. Let the cleaner sit for 10-15 minutes, then wipe it away with a clean rag and water.
See if any discoloration or damage is visible. Use caution when pressure washing. If you are cleaning lannon stone outside, it can be tempting to use a pressure washer to speed up the washing process.