GK Black Spot Remover 5Ltr
GK Black Spot Remover 5Ltr

GK Black Spot Remover 5Ltr

£20.00 EXC VAT
£24.00 INC VAT
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  • Estimated Delivery:Dec 04 - Dec 08

  • Free Mainland UK Delivery : On Orders Over £85 + VAT

Product description

GK Black Spot Remover is a high-performance cleaner designed to easily remove black discolouration and microbiological contaminants from porous surfaces such as stone, render, block paving and concrete.

GK Black Spot Remover is a thixotropic, slightly viscous, non-penetrating liquid. A unique alkali formula containing wetting agents for the removal of organic and non-organic staining.

It thins when agitated allowing good contact with surface contamination, it is non-invasive and allows extended dwell time for the active ingredient to do its work. Brush in and leave for up to 24 hours (depending on need) and rinse.

GK Black Spot Remover can be used before or after GK Pro biocidal treatment, or as a stand-alone treatment.



Black Spot Remover can be applied by brush, sponge, roller or extending pole, choose your preferred delivery method. Many contractors use products such as XLine trolley system & Ionic's Constant Flow system. Always rinse after treatment.

  • AVERAGE COVERAGE: 8m² per litre



  • Always test on a small area of the surface to check compatibility and performance before commencing with the whole area.
  • Remove loose dirt, moss, and other debris from the surface to be treated. A broom or firm bristle brush is ideal.
  • Do not use in wet weather, frost or if rain is forecast within the application period. If used when temperature is below 8⁰C the effectiveness may be reduced and longer cleaning time may be required.
  • Keep pets away until the surface is fully washed and dry.
  • Ideal application temperature between 10⁰C and 30⁰C.
  • The longer GK BSR is left to work (up to 24 hours) the brighter the surface will appear.
  • It may help the process to slightly wet the surface prior to application.
  • NOT recommended for use on wooden surfaces 
  • Whilst applying appropriate PPE should be worn, we recommend protective gloves and eye protection/face protection as a minimum requirement.

Application on render and masonry work:

Reduce biological loading by brushing with GK Pro followed by rinsing or steaming.

On through colour monocouche renders, if metabolised fungi is prominent over a large area, GK Black Spot Remover can be used as the primary treatment. If algae staining remains a top-dressing application of GK Pro will reduce discolouration.



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


Product Data Sheets

GK Black Spot Safety Data Sheet

Product FAQs

What are black spots?

The black spots that grow on your garden stonework are black lichen, a combination of fungi and bacteria. They start life as tiny dust spores growing on the underside of leaves on trees and plants before being carried by the wind and rain onto your stonework.

Encouraged by warm, damp conditions these unsightly spots take two years to germinate and latch onto surfaces, feeding off the mineral in the stonework, spreading slowly as they burrow down into stone, making them difficult to remove even with a pressure washer.

How does GK Black Spot Remover work.?

GK Blackspot Remover is a specially formulated blend of chemicals designed to remove black spots and break down the bonds between the lichen and the stone surface.

Its gel like formulation improves application, and concentrates the active ingredient on the required area, breaking down dirt, stains, and grime in a matter of hours.

Unlike the chemicals used to remove algae and moss (often biocides) black spot remover requires dwell time and agitation to achieve optimal results.

Is it safe on all stone surfaces?

GK Blackspot is suitable for use on almost all treated and untreated stone surfaces. It is safe for use on stone, concrete surfaces, including patios and drives, flagstones, pathways, paving slabs, and sandstone. Typically, the most severe infestations of black spot are found on concrete, York sandstone & Indian sandstone and these can be treated with GK Blackspot remover.

Dwell Time / Application

One of the key areas to applying GK Blackspot is the dwell time after applying the product.

Each patio will be different, some black spots may have only recently formed and are quite easily removed whist on other patios, the black spot may have taken many years to form. The dwell time required to remove these is obviously going to be different, and a thick or concentrated build-up of black spot is going to require both more effort, time, and product than light contamination.

It is recommended that you leave the product on the surface for 24 hours where possible to achieve optimum results with minimal effort, however this is not always practical and therefore you may want to undertake a test patch to see how long the product will take to work for you.

Light contamination may need less than an hour dwell time, with heavier staining taking more than one application, however persistence and repeating the process will usually remove event the toughest of blackspot stains (usually two to three hours will give noticeable results).

GK Black spot removers is a professional strength cleaning solution which has high levels of active ingredient that should be applied neat, using appropriate PPE and workwear.

Before applying make sure the area to be treated is clear and any surface dirt or debris has been removed. You may want to break your patio down into areas, only tackling a section at a time.

Pre-wet your patio so the surface is wet (damp), and the stone is saturated but with no surface water. This will improve capillary action and assist with application. If you think the overspray, or run-off, will affect adjacent plants and lawns use more clean water to wet these areas down. Do not allow the product to run into ponds or encounter fish or other aquatic life (Contains sodium hypochlorite).


Apply GK Black Spot Remover with a pump-up sprayer or watering can (make sure you rinse out the sprayer or watering can afterwards).

Apply the product across the surface area to be treated and leave to dwell, periodically agitating the surface with a stiff brush, ideally the surface should be kept wet for as long as possible which may require additional product to be applied.

Once you have left it for sufficient dwell time, rinse the surface down with clean water (ideally a hose pipe) and for best results pressure wash the patio. Some people like to pressure wash the surface before and after treatment.

It may be necessary, on an extremely heavy build-up to repeat the process. However, you can spot treat odd patches and you do not need to treat the whole area again.


There are some common themes with black spot removal not working as well as expected, however here are a couple of additional pointers to ensure you get the best results.

Ensure you have applied enough product, do not guess the area to be treated, do it accurately, by measuring the length and width and multiplying them together to get an accurate square measurement of the area. This will ensure you have the correct amount of GK Black Spot Remover to treat the area.

Do not try to tackle too big an area in one go, especially if contamination is heavy, working on smaller patches thoroughly can yield better results, and you may need to spot treat areas, repeating the cleaning process more than once.

Make sure the surface being treated has been saturated with water and the stone is wet, but there is no excessive surface water or puddles that will over dilute the product. Remember to agitate the with a stiff brush and extending dwell times can mean using a lot less product than repeating the process. You can also apply additional product to high contamination areas during each treatment cycle.

Power washing or cleaning the surface prior to application can assist by removing dirt and grime from the surface, allowing the product to work better on the black spots as additional detritus has been removed.

Do not confuse other contaminations for black spot, stone is a natural product and may contain other contamination, and reclaimed materials such as flagstones may also have other surface blemishes or stains that are not organic. A test patch will tell you whether you are dealing with an organic infestation or not.

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