Is your patio is covered in blackspots? then you need professional help. This article will cover how to professional remove blackspots from your driveway, patio, path, or other hard surfaces. First by describe what black spots are, chemicals to remove them, what is sodium hypochlorite, how to remove them, then summary,

What are black spots?

The black spots are also known as lichen, an organic fungus, more. Lichens are made up of two or more organisms, fungus being one. The other referred to as photobionts, such as algae. Therefore, black spots are not all made the same as the composition of them can vary. Lichen arrives on patio on the leaves from trees and plants, start off as just dust-like spores. Therefore, the areas of patio closer to greenery is more susceptible to lichen.

They attach themselves to the substrate by way of hyphae, a root like structure.  Once attached they form a ‘crustose’ growth, which is a tight biological layer of the adhering organism. This tight bond provides the roots for them to grow, over time making them almost impossible to remove.

Chemicals to remove blackspots

To remove organics such as lichen, sodium hypochlorite is often used by exterior cleaning professionals. This is due to its oxidising properties, which ultimately turn organics into oxygen. Sodium hypochlorite therefore is only useful against organics, not so useful against carbon or other non-organic marks. There are other chemicals which make claims to aid in removing black spots, although, through experience they come with mixed results. Despite being a strong chemical, sodium hypochlorite is the industry standard in the U.K. for removing organics such as black spots.

Sodium Hypochlorite

What is sodium hypochlorite?

Sodium hypochlorite is essential high strength household bleach. It is chlorine gas mixed with sodium hydroxide, it is a strong disinfectant against organic material and liquid at room temperature. Household bleach is around 5% chlorine, whilst industrial grade is between 12%-15%. SH is a toxic chemical, so when using please wear suitable PPE including, overalls, boots, gloves, goggles and suitable gas mask.

How to remove black spots

To remove black spots first clear the patio, with a hard brush. Then thoroughly jet wash the area. Mix industrial grade sodium hypochlorite with a surfactant which is not ammonia based. If unsure please consult an expert, then add water. We recommend starting with 1 part surfactant to 10 parts SH; then mix 1 part SH-surfactant mixture to tap water.

Water any greenery close by. Then apply the SH-surfactant-water mixture to the problem area on the patio or driveway. Scrub in with a stiff brush, which allows the bleach to penetrate the lichen. Leave for 30 minutes to come to full effect. Finally, use a 15 degree fan jet nozzle on your jet washer and focus on the black spots to remove. Once fully clear, water the greenery again and finish cleaning the area.


Is your patio covered in blackspots? Call Surrey Jet Washing. This article summarises what you should do if you have black spots on your patio, driveway, path, or other hard surfaces. If you are a domestic homeowner, please call your local exterior cleaning expert, or Surrey Jet Washing for advice or guidance. If you are a professional please refer to the attached article for further guidance (Source).