If your slate tiles have developed a green coating or black spots from moss, fungi, or algae, here’s how you can remove them. Moss, algae, and fungi thrive in moist, shady conditions. While this doesn't damage the slate, many prefer to remove them for aesthetic reasons.
What you'll need:
Dampen the area with water. A good tip is to add a bit of dish soap to the water. This reduces surface tension, making the dampening more effective and the subsequent cleaning easier.
Let the solution sit for a few hours.
Scrub the area with a stiff brush.
Note: Do not use a steel brush, as steel residues can cause rust stains on the slate!
It’s usually not necessary, but you can wash the area with a disinfectant like chlorine after the moss or algae removal.
Rinse thoroughly afterward.
Check out this guide for tips on how to clean slate indoors and how to clean slate outdoors and remove all types of stains.
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