Causes and Treatments for Algae/mould Growth in Paint

For most of the people, paint is just the colour on walls, timber, metal, bricks or outside/inside surfaces of their house. Furthermore, from the layman’s point of view, paint is the colour of their house, car, boat or any other object/elements in routine life. Once you paint any surface, several defects are bound to occur on that particular surface. The defects arise as paint film is subjected to the chemical attack of atmosphere, sunlight, dust, and heat, all deteriorating it. Algae/mould growth is one of the several defects on a painted surface. There is a lot of research and many opinions are developed about the causes and treatments for, the growth of algae/mould and they are as follows.

Algae/mould growth, including fungi & lichens, are an increasing problem on both the inside and outside of the buildings, predominantly on painted surfaces. If it occurs on an interior wall then it is potentially harmful as well as aesthetically unappealing.

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Algae/mould can be visible as grey, black, or brown patches on the surface of the paint as fungal or algal growth. Algae/mould growth is unpleasant and can be destructive to paint film. Moisture is a crucial food for the growth of algae/moulds. Algae/moulds growths are presumably to occur in damp conditions or on the surfaces with high moisture content. Also, areas that tend to be receiving little or no direct sunlight can anticipate algae/mould growth at a fast pace. It also occurs at fast pace if painting is carried out over a surface or coating from which algae/fungus not been removed properly. Using lower quality paint (an insufficient amount of fungicide or algaecide) can exaggerate growth of algae/mould.

Treatment Recommendation:

• Algae or mould cannot survive without its food source. So if algae occur outdoor then remove plants or shrub from surrounding areas. And for indoor, remove plants (if any) from the affected wall and also make arrangement for sunlight to fall on the affected wall.
• Paint should have a quality which can make sure that the pores of the surface are not sealed and moisture vapour is not trapped underneath the final coating. If moisture vapour doesn’t disappear or evaporates then the moisture will get trapped underneath the paint film and it might aggravate the process of algae/mould growth.
• If there is any leakage from the concealed plumbing lines then find the source of it and get it repaired, as it increases moisture on the surface and algae/mould can occur.
• Alkalinity is a natural algae/mould inhibitor. Optimum growth condition for algae/mould is typically between pH 5-7. However, it can also easily grow between pH 3-9. Paint has pH of 8-8.8 (it varies for different types paint). The higher the pH of the surface the greater the resistance. So it is advisable to choose paint with higher pH value.
• To distinguish algae/mould whether it arises from dirt or dampness, apply a few drops of household bleach to the discoloured area. If it disappears, it is probably algae/mould due to dust. It can easily be rubbed off with brush and clean it with water and repaint with the desired appearance.
• Clean or remove algae/mould growth with the help of brush and water. Apply bio wash or fungicidal wash or diluted household bleach solution on affected area to stop future growth. Once it dries out, re-paint that affected area with the desired appearance.

It is important to understand and bear in mind that algae/mould are natural, living organisms and therefore able to survive and adapt to any condition. Consequently, it needs periodical observation and cleaning. If periodic cleaning of a surface is not carried out then the layer of contaminants, such as dirt or dust will make a microscopic layer on the surface and this kind of layer will provide an excellent place for algae/mould growth.

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