Caustic soda. Make up about a 5% solution with NaOH from Bunnings in a watering can, then soak the moss with it. wait about half an hour and then it may blast off with a hose. Failing that, a high-pressure cleaner. The caustic has the effect of loosening it
Caustic soda. Make up about a 5% solution with NaOH from Bunnings in a watering can, then soak the moss with it. wait about half an hour and then it may blast off with a hose. Failing that, a high-pressure cleaner. The caustic has the effect of loosening it