Categories: Algae Remover, All Products, All Products, Black Spot Remover, Brick, Concrete and Grout Cleaner, Cleaning Chemicals, Driveway Cleaner, Gk Products, Paths and Patio Cleaner, Render Cleaner

Tags: Professional Grade

GK Black Spot Remover 5Ltr

Name: GK Black Spot Remover 5Ltr
Brand: GKProductsUK
SKU: CHE / R04/A / 5LTR
Price: 19.99 GBP
Availability: InStock

SKU: CHE / R04/A / 5LTR Brand: GKProductsUK

£19.99 Ex VAT: £16.66

GK Black Spot Remover is a professional-grade patio black spot remover formulated to eliminate lichen-based black spot staining, and non organic staining such as pollution from natural stone, block paving, concrete, and render.

Unlike general-purpose algae removers, it targets the unique chemistry of black spot lichen, breaking down the bonds that anchor it to the surface, and can be left to dwell on the surface for up to 24 hours for maximum penetration and results.

Why Black Spot Needs Its Own Dedicated Treatment

Black spot is not the same as algae, and it cannot be removed with the same products. The black spots that appear on patio stone, driveway paving, and garden surfaces are black lichen, a combined organism of fungi and bacteria that begins life as airborne spores and, once settled on a porous surface, anchors itself deep into the material using root-like structures called rhizines.

These penetrate below the surface layer, which is why pressure washing shifts the visible staining temporarily but leaves the organism intact and the spots return within weeks.

Removing black spot properly requires a black spot remover formulated specifically for lichen chemistry. GK Black Spot Remover uses a unique alkaline formula enriched with wetting agents that targets both organic and non-organic staining, breaking down the molecular bonds between the lichen and the stone rather than simply bleaching or displacing the surface layer. The result is a genuine removal, not a temporary clean.

Surfaces: Where GK Black Spot Remover Performs

GK Black Spot Remover is suitable for use on virtually all treated and untreated natural stone and hard paving surfaces, including:

Patio slabs and paving: natural Indian sandstone, York stone, limestone, and slate, where black spot infestation is most commonly found and most severe
Concrete paving and driveways: block paving, imprinted concrete, and concrete slabs affected by lichen staining
Render and masonry: external render surfaces including through-colour monocouche render (see application notes for specific guidance)
Flagstones and pathways: any hard landscaping surface where black spot lichen has established
Garden stone features: stone walls, raised beds, stone ornaments, and garden structures

It is not suitable for use near ponds or watercourses, and care should be taken around plants and lawns during application (see FAQs below).

Standalone or Combined Treatment

GK Black Spot Remover can be used as a standalone patio black spot remover for surfaces with exclusively lichen-based staining, or in combination with GK Pro biocidal treatment or GK Multi-Surface Cleaner and Sanitiser, where both black spot and algae or mould growth are present.

The two-product approach is particularly effective on heavily contaminated surfaces: GK Black Spot Remover addresses the lichen chemistry, while GK Pro handles broader biological loading and provides residual activity to inhibit future regrowth.

For render and masonry with widespread metabolised fungal growth, the recommended sequence is GK Black Spot Remover as the primary treatment, followed by GK Pro as a top-dressing to address remaining algae discolouration.

Coverage and Value

One 5-litre bottle covers up to 30 square metres at full application rate. For heavily contaminated areas of thick lichen, long-established black spot and multi-year accumulation, a more generous application and longer dwell time are recommended, which will reduce coverage per bottle. For lighter or more recent staining, the product goes further.

For advice on the right approach for your surface type or scale of contamination, contact our team on 07557 111 297 or email sales@gkproductsuk.com. Free delivery on orders over £60.

The Semi-Gel Advantage

GK Black Spot Remover is formulated as a semi-gel, slightly viscous liquid. This is a deliberate design choice. A standard liquid solution runs off vertical and angled surfaces before it has time to work, and disperses quickly on flat paving under its own weight. The semi-gel consistency concentrates the active ingredient on the surface and holds it in contact with the contaminated area for far longer than a thin liquid would allow.

When agitated with a stiff brush or by working the product into the surface, the gel thins and flows, improving contact with the surface at a capillary level. This combination of surface contact and deep penetration is what makes extended dwell times practical and effective: the product stays where it's needed for as long as it takes to work.

Key Features

Purpose-formulated patio black spot remover: alkaline formula with wetting agents designed specifically for lichen-based black spot staining, not a repurposed general-purpose cleaner
Semi-gel consistency: holds the active ingredient on the surface for extended dwell periods; thins on agitation for deep capillary penetration
Up to 24-hour dwell time: longer contact time means more effective removal, particularly on established or severe infestations
Suitable for natural stone, concrete, block paving, render, and masonry: including Indian sandstone, York stone, limestone, and concrete paving
Standalone or combined treatment: use alone or alongside GK Pro biocidal treatment for broader biological contamination
Professional grade: high concentration of active ingredient, applied neat using appropriate PPE
Targets organic and non-organic staining: addresses the full range of discolouration associated with black spot, including metabolised fungal residue

Surface Preparation

Clear loose debris, moss, and dirt from the surface with a broom or stiff bristle brush before applying. For heavily soiled surfaces, a pressure wash prior to treatment removes excess detritus and allows the product to work more directly on the black spot staining.

Pre-wet the surface with clean water so the stone is damp and saturated but without standing puddles. This improves capillary action and helps the product penetrate the surface. Wet down any adjacent plants, lawn edges, or areas where run-off may reach, and do not allow the product to enter ponds or encounter aquatic life.

Application

Apply GK Black Spot Remover neat using a pump-up garden sprayer or watering can. Work in manageable sections rather than attempting to treat a large area in one pass, as this gives more control over dwell time and product volume per area. Apply evenly across the surface to be treated.

Periodically agitate with a stiff brush during the dwell period to thin the gel and improve surface contact. Keep the surface wet for as long as possible, adding more product if required, as this extends the dwell time and improves results. For maximum effectiveness, allow up to 24 hours' dwell time where practical.

Rinse thoroughly with clean water after the dwell period, ideally using a hose or pressure washer. For persistent or very heavy staining, the process can be repeated, or spot treatment applied to remaining patches without retreating the entire area.

Weather and Temperature

Do not apply in wet weather, frost, or when rain is forecast during the treatment period. Effectiveness reduces below 8°C, requiring extended dwell times to compensate. Ideal application temperature is between 10°C and 30°C.

PPE

Wear appropriate gloves and eye or face protection during application. GK Black Spot Remover is a professional-strength concentrated solution so handle with care and store securely away from children and animals.

Storage

24 months from date of manufacture in the original unopened container in a clean, dry area. Do not store below 5⁰C.

Download Spec Sheet PDF

See The Results

Before After

GK Black Spot Remover

Before After

GK Black Spot Remover 1

Frequently Asked Questions

Black spots on garden stone and paving are caused by black lichen, a combined organism of fungi and bacteria. They begin as airborne spores that settle on porous surfaces, then anchor deeply into the stone using root-like structures called rhizines. This is why black spot returns after pressure washing: the visible staining is removed, but the organism embedded in the stone is left intact and regrows from the surface.

Algae and black spot lichen are fundamentally different organisms requiring different chemistry to remove. Algae sits on the surface and responds to biocidal treatments. Black spot lichen penetrates the surface and requires an alkaline formula with extended dwell time to break down the bonds between the lichen and the stone. Using an algae remover on black spot will produce limited results.

Dwell time should be matched to the severity of staining. Light or recently formed black spot may show results within one to two hours. For moderate contamination, two to three hours typically produces visible improvement. For heavy, long-established lichen, 24-hour dwell time is recommended and will give the best results with the least product and effort. The longer the product dwells, provided the surface remains wet, the better the outcome.

As the product works, the black spot staining will begin to lighten and break down. Agitating the surface periodically with a stiff brush during the dwell period helps confirm the product is penetrating. After rinsing, even partially treated surfaces will show improvement. Repeat treatment or extended dwell time is the solution for any remaining spots, rather than abandoning the process.

Yes. GK Black Spot Remover is suitable for Indian sandstone, York stone, limestone, and other natural stone paving. Indian sandstone and York sandstone are, in fact, among the surfaces where black spot infestations are most commonly severe, and the product is formulated to treat these surfaces effectively. Always conduct a small test patch before full application.

Yes, and for heavily contaminated surfaces this combined approach is recommended. GK Black Spot Remover addresses the lichen staining, while GK Pro provides broader biocidal treatment and residual protection against regrowth. On render with widespread metabolised fungal growth, apply GK Black Spot Remover first, then GK Pro as a follow-up top-dressing to address remaining algae discolouration.

If black spot returns relatively quickly after treatment, it usually indicates either insufficient dwell time, inadequate product volume for the contamination level, or that the surface was not kept wet throughout the treatment. Following up with GK Pro after black spot treatment provides ongoing residual biocidal protection and inhibits regrowth.

The product contains sodium hypochlorite and should not be allowed to run into ponds or contact aquatic life. Pre-wet surrounding plants and lawn edges before application to dilute any overspray or run-off. The product may scorch foliage but should not kill established plants, and lawns recover quickly.

Why us

Why Choose GK?

We believe in constant innovation. Our team is dedicated to finding new and better solutions that the industry needs, providing the most effective, least harmful, and safest professional-quality products to our customers.

We use high-quality active ingredients that deliver superior, longer-lasting results. By avoiding harsh chemicals, we ensure a safer cleaning process for surfaces and substrates, as well as for the environment. Whether you're an industry professional or a DIY enthusiast, you can expect our products to provide a thorough, lasting clean that leaves your surfaces pristine.

So if you're tired of products on the market delivering a sub-par clean, want to experience professional-quality results, or even find comfort in knowing that your cleaning products are safer for your surfaces and the environment, then why not try our range of GK cleaning products for yourself?

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