HG Headstone Cleaning Spray 500ml Under the influence of various weather conditions, mould, algae & moss growth occurs on natural stone, plasterwork, masonry, etc. HG headstone cleaning spray removes stubborn soiling with ease. Spray HG headstone spray from approx. 5 cm distance on the surface to be cleaned & leave to work for 25 minutes. Any remaining dirt can be removed using a cloth or brush. Then rinse the surface thoroughly. Repeat the treatment after approx. 30 minutes in the case of very stubborn soiling. Half a litre of spray is sufficient for approx. 3m surface area.