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Removing Black Spot: How to Remove Black Spots from Patios & Stone

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Patio before and after black spot removed


In the world of outdoor maintenance, few challenges are as persistent and frustrating as the dreaded black spot. These unsightly blemishes, often found marring the beauty of patios and stone surfaces, can turn what should be a source of pride into a point of concern.

Black spot infestation removed from patio
Black spot infestation removed from patio

In this guide, we'll delve into the various aspects of tackling this common issue. From selecting the right patio black spot remover and mastering the application techniques to tools & equipment, we'll cover everything you need to know. We'll also address important considerations like safeguarding surrounding vegetation, protecting aquatic life, and ensuring the safety of your stone surfaces during the cleaning process.

So, whether you're dealing with a few stubborn spots on your patio or a widespread issue across various stone surfaces, join us on this journey to reclaim the beauty of your outdoor spaces.

Understanding Black Spot

What is Black Spot?

Black spot, often mistaken for simple dirt or grime, is actually a form of black lichen that clings tenaciously to stone surfaces. This organism thrives in outdoor environments, particularly on porous natural stone, like an Indian Sandstone patio. Its presence is not just an aesthetic issue; over time, black spot can lead to the deterioration of your patio and stone surfaces, making their removal crucial for long-term maintenance. For a more detailed insight into black spot check out our 'What is Black Spot? An Essential Guide For Property Owners' article.

Patio before and after black spots and lichen removed

Preparation for Removing Black Spots

Initial Steps

Before you start the process of removing black spots, it's important to prepare the area. This includes clearing any loose debris and ensuring that nearby vegetation and aquatic life are protected from potential chemical exposure. Always test your chosen patio black spot remover on an inconspicuous area of the patio to gauge its effectiveness and potential for causing damage.

Safety Precautions

When dealing with chemicals, safety is paramount. Ensure you're wearing appropriate protective gear and take measures to prevent direct skin contact with the cleaning fluid. Be mindful of the surrounding environment to avoid unintended harm to your garden or local wildlife.

Choosing the Right Black Spot Remover

Types of Removers

The market offers a variety of patio black spot removers, ranging from acid-based cleaners to specially formulated non-acidic solutions. Acid-based cleaners can be effective but may pose a risk to certain stone types and the environment. Non-acidic removers, while gentler, may cost more and require more time to show results.

Selecting for Your Stone Type

The choice of black spot remover should be tailored to the type of patio or stone you're dealing with. For sensitive materials like natural stone, for example Indian sandstone, a specially formulated cleaner that won't cause discoloration or damage is ideal. For more resilient stone types, a stronger solution might be necessary to tackle stubborn black spots.

Application Techniques

Effective Application

The key to successfully removing black spots lies in the application of the cleaning fluid. For an even distribution, consider using a pump sprayer or a watering can. This ensures that the entire surface area is adequately covered.

Targeted vs. General Cleaning

For targeted removal of persistent black spots, apply the cleaner directly to the affected areas and allow it to sit for the recommended duration. For general cleaning of patios and stone surfaces, a broader application may be necessary.

The Role of Pressure Washing

Pressure washing can be an effective tool in the removal process, especially for larger patio areas or extensive stone surfaces. However, it's important to use this method correctly to avoid damaging the stone or patio surface.

Ensure you use the correct nozzle or adjust the lance to a fan setting. Set the pressure settings according to the resilience of your stone surface and always test on a small, inconspicuous area first.

Where natural stone surfaces are concerned, power washing is often a better alternative to pressure washing due to the incorporation of heat. Check out our what is the difference between power washing and pressure washing article to find out more.

Safety and Environmental Considerations

Handling Chemicals Safely

When using chemical cleaners, it's crucial to be aware of their potential to release toxic gases, especially when mixed with other substances. Always read and follow the instructions carefully, and ensure good ventilation in the area you're working in and wear personal protective equipment (PPE) such as goggles, eye protection and gloves.

Protecting the Environment

Consider the environmental impact of your cleaning process. Avoid washing cleaning fluids into your garden or areas where they can affect aquatic life. Choose an eco-friendly patio cleaner or stone cleaner when possible, and always dispose of any leftover chemicals responsibly.

Tools and Equipment Required to Remove Black Spot

To effectively remove black spot from your patio and stone surfaces, having the right tools and equipment is crucial. Below is a list of products, each linked to where you can purchase them.

Patio Black Spot Removal Products

Choose a remover suitable for your specific type of stone or patio surface. The following are popular choices.

Patio Black Spot Remover
Xtreme Black Spot Remover
Ultimate Black Spot Destroyer

Natural Stone

Natural Stone

Block Paving

Paving Slabs

Indian sandstone

Block paving

Pump Sprayer

A pump sprayer provides a controlled method for applying the remover.

Pressure Washer

Selecting the right pressure washer is crucial for cleaning large, heavily soiled areas effectively. Machines with lower pressure outputs can struggle with such tasks, making your job harder, if not impossible.

Top Tip: Pressure washers with a higher pressure output can tackle tougher cleaning jobs more effectively. But don't overlook the flow rate – a higher flow rate means you can rinse surfaces faster, significantly improving your overall cleaning efficiency.

The right balance of high pressure and flow rate can make a substantial difference in your cleaning results and routine. Investing in a pressure washer that excels in both these aspects is key to superior cleaning performance.

Kärcher K 4 Power Control

Kärcher K 7 Premium

Hyundai Pressure Washer

Power source: Electric

Pressure (Bar): 130

Pressure (PSI): 1885

Flow rate (LPM): 7

Hose Length: 8m

Power source: Electric

Pressure (Bar): 180

Pressure (PSI): 2610

Flow rate (LPM): 9

Hose Length: 10m

Power source: Fuel/Petrol

Pressure (Bar): 275

Pressure (PSI): 4000

Flow rate (LPM): 15

Hose Length: 15m

To gain a better understanding of pressure washers and pressure washing check out our Pro Pressure Washing Tips article.

Step-by-Step Application of Black Spot Remover

Preparing the Patio

  1. Identify Affected Areas: Begin by identifying the areas of your patio affected by black spots.

  2. Clear the Area: Remove furniture and other items to gain unobstructed access to the stone or patio surface.

  3. Sweep: Thoroughly sweep the area to ensure area is free from debris such as leaves.

  4. Protection: Protect any plants or ponds that require protecting.

Applying the Remover

  1. Choose the Right Remover: Select a black spot remover suitable for your patio's material and the severity of the infestation.

  2. Test: If you haven't already done so, apply the remover to a small inconspicuous area. If it doesn't cause an adverse reaction proceed with the next step.

  3. Apply Generously: Apply the remover generously, following the manufacturer's instructions. Ensure even coverage over the affected areas. Be mindful that depending on the remover you are using it may kill vegetation and stain fabrics.

  4. Agitate: Use a stiff brush to agitate the surface by moving the brush back and forth across the surface to encourage the chemical to react and speed up the process.

  5. Allow Dwell Time: Let the remover sit for the recommended time to penetrate and soften the black spots. This dwell time is crucial for the product's effectiveness.

Physical Removal and Washing

  1. Scrub the Area: After the dwell time, scrub the affected areas vigorously with a stiff-bristled brush to dislodge the softened black spots.

  2. Pressure Washing: Use a pressure washer to rinse away the remnants of the black spots and the remover. Be cautious with the pressure setting to avoid damaging the patio surface.

Post-Application Steps

  1. Repeat if Necessary: For persistent black spots, the patio area may require a second application of the remover and additional scrubbing may be required.

  2. Rinse Thoroughly: Rinse the treated area thoroughly with a pressure washer or a garden hose to remove any residue of the remover.

  3. Dry and Inspect: Allow the patio to dry completely and inspect the area. If necessary reapply and repeat the process.

Aftercare and Maintenance

Post-Cleaning Care

After successfully removing black spots, it's important to focus on the aftercare to keep your patio clean. This includes regular inspections and cleaning to maintain the aesthetic appeal and integrity of the stone. Sweep regularly and ensure areas are kept free from leaves, dirt and grime to prevent black spots and other organic matter from returning. For areas like patios and paths this step is crucial in prolonging their lifespan and appearance.

Preventative Measures

To prevent future black spot growth, you may want to consider applying a sealant to surface, especially if they are porous like natural stone or sandstone. This can create a barrier against moisture and organic growth, reducing the likelihood of black spots reappearing.

Routine Cleaning

Incorporate routine cleaning into your maintenance schedule. Use a mild patio cleaner that is suitable for your specific type of stone. Regular cleaning not only keeps black spots at bay but also helps in managing other forms of surface contamination like green algae, dirt, and grime.


Removing black spots doesn't have to be a daunting task. With the right approach, products, and techniques, you can effectively tackle this common issue and maintain the beauty of your outdoor spaces. Remember, regular maintenance and preventative measures are key to ensuring that black spots remain a problem of the past.

Whether you're dealing with a newly laid patio or an older stone surface, the satisfaction of restoring its beauty is unmatched. So, roll up your sleeves and get ready to give your patio the care it deserves.

Frequently Asked Questions

What is the best black spot remover?

The best black spot remover is one that is specifically formulated for the type of stone you are treating. For natural stone surfaces, a non-acidic remover is often recommended as it is less likely to cause damage. For more resilient stones, an acid-based cleaner might be more effective.

How can you remove black spots?

To remove black spot, start by choosing an appropriate black spot remover for your stone type. Apply the cleaner onto the affected area using a pump sprayer or similar tool. Allow it to sit for the specified time, then rinse thoroughly with clean water, using a pressure washer if necessary. For stubborn spots, a second application might be required. Remember to always test the product on an inconspicuous area prior to full application.

What removes black spot on patios?

Removing black spot on patios typically involves using a patio black spot remover such as a professional grade outdoor cleaner. These are specially formulated to tackle the tough lichen that causes black spots. Dilute the cleaner if necessary and apply the solution over the affected area, let it sit, and then rinse off. For patios with stubborn black spots, consider using a pressure washer for more effective removal. It's important to choose a remover that is suitable for the patio material, whether it's natural stone, Indian sandstone, or block paving.

What chemical kills black spot?

The chemicals that effectively kill black spot are usually found in patio black spot removers. These can include various active ingredients, with some being acid-based and others non-acidic. The key is to use a product that contains an active ingredient capable of penetrating the stone surface to target and kill the black lichen causing the black spots. However, it's crucial to be cautious of the potential release of toxic gases when using chemical-based cleaners and to ensure they are safe for your specific type of stone.

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