How to remove lichen (including "black spot") from concrete, brick, render & tiles

June 21, 2017 4 Comments

Several customers asked us for our suggestions as to the best way to remove lichen (including "black spot" which is black lichen) by softwashing.

Lichen are white, brown, yellow and black (i.e. "black spot") growths that grow 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 rarely effective.

Start by watching this video to get a brief overview of, and basic insights into, the best way to remove lichen (including "black spot") by softwashing:

Lichen (including black lichen, or "black spot") attach themselves to, and actually grow into, the surfaces of roofs, paths and walls

The best way we've found to remove lichen is to first kill it by treating with Benz Tornado Cleanze, applied neat. 

Quick tip: Tornado Cleanze contains a particularly potent surfactant that can foam up when rinsing. To reduce foaming use low-pressure and minimise agitation when rinsing.

Or, treat with Benz Lightning Cleanze (dilute according to the severity of infestation and the results of your test patch).

Follow this treatment with a light pressure/jet wash, working the dead lichen spots with the jet to free them from the surface.

If some infestation remains, repeat the treatment.

Finally, treat with Benz Bio Cleanze. This will continue to deep clean over several months, killing any remaining spores, while also providing residual protection against recolonisation.

Important safety tip: If children or animals will walk on the treated surface, apply Bio Cleanze at only 50:1, keeping them well away from the working area and allow the surface to become completely dry before allowing them back.

Pressure (aka jet/power) washing and wall render

Important note re pressure washing: Using a pressure/power/jet washer on lichen without first killing it with Lightning Cleanze or Tornado Cleanze – which means the growths will still be well rooted into the surface –  may damage the surface because the pressure will rip the still living roots out. Whereas after treatment the roots will be dead and will to some extent have released their grip.

We've found that when first killed with Lightning Cleanze or Tornado Cleanze jet washing will lift the roots out much more easily.

Important note re wall render: When treating render we generally do not recommend high-pressure jet washing, as it can damage the delicate surface of modern renders such as KRend and Weber.

Use of a jet washer, set to low pressure and/or using a wide angle fan jet, is fine for rinsing however. The pressure of the water when it contacts the render should be approximately that of tap water pressure.

The combination of Lightning Cleanze or Tornado Cleanze followed by a light pressure wash will remove the majority of lichen.

Bio Cleanze will then work through time – from 6 weeks to 12 months – to remove any remaining lichen and kill any remaining spores deep into the surface.

The actual time it takes Bio Cleanze to work will depend on factors such as:

• The local environment
• Level of infestation
• How long the infestation has been allowed to grow into the surface
• Prevailing weather
• The exact type of biological growth ("black spot" can be caused by different biological species)

Time and the natural weathering of sun, wind and rain will usually lift the lichen from the surface once it is dead and it will disappear within a year

Enrol your customers onto your ongoing "Clean & Maintain" softwash programme

Patio slabs badly infested by black lichen ("black spot") before softwashing:

The same patio slabs after black lichen ("black spot") has been removed by soft washing:

A path badly infested with black lichen ("black spot") and black algae in which the black lichen had grown deeply into the concrete slabs:

The same path after the black lichen / black spot and black algae has been removed by softwashing: 

We've found the following sequence to be a highly effective way to remove black and white lichen:

1)  Brush and hose down, or lightly pressure wash, the surface to remove loose organic matter.

2)  Treat with neat Tornado Cleanze, or Lightning Cleanze at 4-5:1 dilution, brushing the chemical into the lichen to help penetration (multiple treatments can be beneficial for badly infested surfaces).

3) Rinse and observe the results.

4)  If necessary apply repeat treatments of Lightning Cleanze or Tornado Cleanze.

5)  Lightly pressure wash any remaining black lichen, which will now be dead and its roots will more easily lift from the surface. (even a domestic pressure washer will do the job after a softwash treatment, as we have proved).

6) Apply Bio Cleanze at 50:1. This will find its way deep into the surface, clean out any remaining lichen spores, and provide long-term residual biocide protection against re-colonisation.

7)  When the first signs of algae or lichen growth return, or as a regular 6-18 month regular re-treatment, it is usually sufficient to apply Bio Cleanze at 50:1 (40:1 in cold weather) alone as part of your ongoing maintenance plan.

Quick tip: Offering your customers a "Clean & Maintain" ongoing maintenance plan will give them a perpetually clean property and will give you a continual stream of lucrative repeat softwash business.

Lichen usually takes a long time, even years, to return but sometimes, in damp, shaded areas of paths and patios, algae will be noticed sometime during the 6-18 months following treatment with Benz Softwash biocides.

At this point a quick "spray & go" with Bio Cleanze is all that is required to keep the surfaces immaculately clean and your customer very happy.

Click here to learn about our free online softwash training

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Benz soft washing how-to videos cover every aspect of soft washing. We show you how to soft wash domestic and commercial roofs, paths and drives, tarmac, concrete, walls, wall render (including KRend, Monocouche, Weber), wet pour safety surfaces, tennis courts, car parks, wood decking, fences, sheds and more ...

 
Our sincere wishes for a good life and a profitable business,

Ben, Leo & Fiona

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