Homeowners often use baking soda and a stiff brush to remove their driveway stains; pour a generous amount of baking soda over the stain and scrub it well with the brush. Let it sit for at least 30 minutes so that the baking soda has time to remove stain particles, then rise off with a hose.
'Due to moisture and shaded areas, black spots on patio slabs are often caused by mold, mildew, or lichen growth,' explains Amber Noyes, Horticulturist and Editor, Gardening Chores.
Stubborn stains may require extra action. Try mixing one cup of trisodium phosphate (TSP) in a gallon of hot water and pouring this over the stain. Let it soak for at least 30 minutes and scrub with a brush. Wash off with your hose and repeat as necessary.
If your concrete has ugly charcoal-gray or black streaks or splotches, black algae is probably the culprit. Black algae can grow on many outdoor surfaces such as concrete or roof shingles and will thrive as long as there is moisture and sunlight.
Black algae (Gloeocaspa Magma) appears on your driveway as dark grey or black streaks and smears. Black algae is a type of fungus that thrives in moist areas, in both the sun and shade. From a distance, it looks like ordinary garden dirt, but you can't wash it away with the hose.
Lichen are white, brown, yellow and black (i.e. "black spot") biological growths that live on slate and concrete tiled roofs, as well as on concrete paths, monoblock drives, brickwork, and occasionally on wall render. Lichen can be very tough to remove and pressure washing alone is ineffective.
Excess Water
As the water evaporates to the surface and soaks into the cement that is an ingredient of concrete, it leaves behind darker spots where the cement contains more moisture. These will fade over time as the water eventually soaks into or evaporates out of the slab.
Black mold growth on concrete takes on the appearance of black spots, larger circular formations, or complex solid growth over an entire wall. Black mold in small amounts could also be mistaken for common mildew around damp basement areas but is much more dangerous.
Use a detergent such as Dawn or Ajax dishwashing liquid mixed with water to brighten a concrete patio that hasn't been cleaned in a while. Just as you would regularly vacuum the floor and dust your furniture inside your house, you should keep your patio clean so it's ready at a moment's notice to entertain.
Whether your patio is sealed concrete or cement, or even sealed concrete pavers, a bleach and water solution makes it easy to clean away built up soil, stains from leaves and pollen, mold, mildew and algae.
It's one of the best ways to remove oil stains. But because bleach is a strong product, we recommend that you wear old clothes for this method. Spray it on the surface and allow it to dry for about 10 to 20 minutes, depending on the stain. Start scrubbing with a brush before rinsing with clean water.
The Wet & Forget Xtreme Reach™ Hose End product is the perfect solution to removing those pesky black stains. Easily reach the high areas of your roof without a ladder and with no scrubbing or pressure washing!
While researching how to remove patio black spots you may have come across “Sodium Hypochlorite” which is a very strong bleach and while it may remove black spots, it will also damage the surface of anything it comes into contact with.
Combine 1 teaspoon of hydrogen peroxide and 1 teaspoon of milk in a glass bowl. Dip cotton pad or Q-tip in the bowl and apply to dark spots. Leave on for 15 minutes. Rinse with lukewarm water and finish off with your favorite serum and moisturizer.
Vinegar and Baking Soda
Simply fill a spray bottle with equal parts water and vinegar (or water and baking soda), and add a little bit of liquid dish detergent. Spray the mixture on your concrete surface and let it sit for about 30 minutes. Then scrub and rinse your concrete.
Cleaning concrete with muriatic acid can be a highly effective solution if used correctly, providing ultra-bright white concrete and removal of many types of stains. In one application, you can remove rust stains, oil stains, algae, and paint splatter with a quick chemical application followed by pressure washing.
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.
While it is possible to use bleach to kill mold as well, experts agree that vinegar is a much better option. Unlike bleach, vinegar can effectively kill the mold at the root, which means it's less likely to return. Vinegar is also less toxic than bleach, making it a better choice for household use.
Black mold, a type of mold that can potentially pose health risks to humans. It produces mycotoxins, which are toxic substances that can be released into the air when the mold is disturbed or when it grows on damp or decaying materials.
Concrete discoloration can be attributed to inconsistent mixtures, too much or not enough water, and low-quality materials. Tracing back to the process can take the valuable time needed for construction.
Sweep off or vacuum up any loose dirt, dust, and debris from the concrete surface. Using a garden hose, wet the concrete. Then, apply a mixture of trisodium phosphate and water, scrubbing the solution onto the surface using a stiff-bristled broom. You can also use a pressure washer for this step.
While mold only feeds on organic materials, it can grow on any surface, especially concrete. While concrete may not supply an abundance of organic material, it provides just enough mold to spread to other areas of a building.
Baking soda (1 1/2 tablespoons) and horticultural oil (3 tablespoons) in water (1 gallon) has also been shown to be effective for black spot control. For most products, you will need to treat every seven to 14 days from bud break until wet weather subsides.
Because hydrogen peroxide has very strong bleaching properties, it can lighten dark skin areas such as dark spots caused by sun damage, aging, scars or hormonal changes. However, this process will irritate and destroy the user's skin a lot.