Black spots appear when mould and algae have settled into the pores of the paving stones, but before you reach for one of the best patio cleaners on the market and get stuck into how to clean a patio, it's worth considering how to avoid the issue occurring in the first place, and it can help to have a good drainage ...
This is a common problem. It could either be mildew, or a reaction from tannin in the wood. Given that you have black residue on rocks, it may be mildew. If the rocks/stones are near the deck/pergola, it may just be stained water dripping on to them and then staining them.
Stontex Black Spot Remover is a professional grade outdoor cleaner which eliminates all traces of stubborn grey lichen and black spots from all masonry and stone surfaces. This one off treatment eradicates black spots and algae with ease.
The patio black spots that grow on your garden stonework are actually spots of black lichen. The spores from the black lichen start life as tiny dust-like spores growing on the underside of leaves on trees and plants. These spores are carried, by the wind and the rain, onto your stonework in their millions.
A dish soap, like Dawn, is a safe place to start. The surfactants in dish soaps are designed to remove oil and grease, they're gentle enough to be used without issue on your pavers. In a bowl or bucket, mix the soap with water and pour it onto the stain and agitate. Rinse and repeat if needed.
You can't cover your patio with copper sheets, but you can spray on a liquid solution of copper that will soak into the top surface of the concrete pavers. This copper will stop the growth of the pesky green and black organisms in their tracks.
If you have greenish-black stuff on your concrete patio, it's probably mold, mildew, or moss. Damp or moist conditions from rain or humidity can encourage mold and mildew to grow in those nooks and cracks of concrete pavers or bricks.
Black stains on stone are quite often caused by a cyanobacteria (Gloeocapsa sp. that not only stain the stone black, but also increase water absorption by penetrating veins in the stone (or marble, for example) leading to honeycomb weathering damage to the stonework.
Sanding and chiselling will leave unsightly marks on your paving, bleaching can work well but you have to be careful not to kill your plants and dilute your bleach to the correct level, some people recommend using this method only in the winter months to avoid damage to plants but you still need to be really careful ...
What's Causing It? Simply put, black stains on flagstones are caused by certain types of mold and mildew.
It's a lichen that looks like a spot or smudge, basically black marks in various sizes. It is a living organism which inhabits the surface of garden stonework, this can be on both floors and walls. Black spot on sandstone tends to be more difficult to remove than black spot on block pavers.
On granite, sandstone, slate, or quartzite, you can use a 1/2 teaspoon of hydrogen peroxide or a few drops of ammonia directly on the stain and remove it with a damp cloth. Use your normal cleaning solution on marble, limestone, onyx, or travertine.
Let us start by saying that bricks do not “turn black”. That is not supposed to happen. This black spot is developing probably due to one of these three things: excess moisture, dirt, or mold. Bricks are a completely natural material.
Alexandrites are rare and highly-prized gemstones, which were first discovered around 1830 in Russia, and named after the future Czar, Alexander II, and later found in other countries such as Brazil and Sri Lanka1.
Desert varnish is the thin red-to-black coating found on exposed rock surfaces in arid regions. Varnish is composed of clay minerals, oxides and hydroxides of manganese and/or iron, as well as other particles such as sand grains and trace elements. The most distinctive elements are manganese (Mn) and iron (Fe).
Black spots appear when mould and algae have settled into the pores of the paving stones, but before you reach for one of the best patio cleaners on the market and get stuck into how to clean a patio, it's worth considering how to avoid the issue occurring in the first place, and it can help to have a good drainage ...
If allowed to set seed properly, black mould will continue to spread and grow. It attaches itself to natural materials both inside and outside the home, including natural wood, stone, wicker and paper materials.
Vinegar Solution
Spraying a vinegar solution (1 cup of vinegar per gallon of water) onto the surface, saturating it fully, should kill most strains of mold. Vinegar spray can be followed by power washing or manual hand scrubbing to remove the dead mold.
For a natural solution for getting rid of black mold, combine one part baking soda with five parts distilled white vinegar and five parts water in a spray bottle.
Tips to Keep Black Mold Away Longer. Repair leaks that keep surfaces wet. Add a dehumidifier and use heating and air conditioners to help reduce moisture levels. Install moisture barriers in basements.
Scrub with Bleach and Water
Prepare a 50/50 solution of bleach and clean water to use with a soft nylon brush or pad. Allow the bleach and water solution to sit for about 15 minutes after the first scrubbing session, then finish the job by rinsing with clean water and using natural stone cleaner and sealant.
To clean paver slabs, you can use a detergent, such as Dawn, or a vinegar-water solution that is gentle enough to effectively clean without causing damage to your concrete pavers.
White vinegar is good for cleaning pavers, though it's also acidic enough to erode the stones' surface. Diluted vinegar can be used safely to clean paving stones, though it should be used sparingly and infrequently to protect your paving from damage.