CareCleaning the sprayhood - how to remove mould stains and algae

Hauke Schmidt

 · 09.04.2026

Care: Cleaning the sprayhood - how to remove mould stains and algaePhoto: YACHT/A. Lindlahr
Visual inspection. Mould stains usually occur on the inside of the sprayhood
After a few years, ugly signs of use appear on the sprayhood: green seams and stains on the outside, black mould stains (spak) on the inside. The boat cover becomes permeable, dries slowly and provides ideal conditions for algae and mould. We show you how to clean the sprayhood and tarpaulin - yourself or with a professional - and make the fabric waterproof again.

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Unfortunately, green soap and scrubbing don't help when cleaning the sprayhood. The boom cover also suffers: The fabric soaks when it rains, dries slowly and no longer properly protects the sail underneath. This encourages further infestation by mould and algae. Thorough cleaning and new impregnation are necessary - either by yourself or by a specialist.

Professional cleaning: Expensive, but thorough

One option is to have the sprayhood professionally cleaned by a sail or tarpaulin maker. As a rule, they will give the canopy to a specialised large-scale cleaning company such as Zonklaar further. The prices depend on the weight of the tarpaulin.

Cost example:

  • Sprayhood for a ten-metre yacht (approx. 3.5 kilograms): approx. 270 euros
  • Tree tarpaulin: another 210 euros
  • Total: approx. 480 Euro
  • Duration: Up to four weeks (including return transport)

If you want to succeed faster and save costs, you can take the initiative.

Clean sprayhood and tarpaulin yourself

Cleaning takes place in three steps: pre-cleaning, mould stain removal and impregnation. The drying times between the work steps alone keep you busy for a good two days.

The grip area on the rear edge of the sprayhood is very dirty
Photo: YACHT/H. Schmidt
The first step is to remove superficial dirt. However, you should not expect miracles

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Combat mould stains

The intrepid tackle algae and spores with diluted sanitiser. The sodium hypochlorite it contains makes short work of organic soiling. This is not really a problem with synthetic fibre cloths, but the effect is difficult to control and cotton covered threads are often used for the seams. The natural fibre swells when wet and thus ensures rainproof seams. However, the aggressive chlorine compound damages the cotton and significantly shortens its service life. It is therefore better to use special tarpaulin cleaners, such as those available from the MTS mould service or Ultramar are available from Holland. When used correctly, the risk of excessive seam wear is significantly lower. Both suppliers have been on the market for decades and their products have been tried and tested thousands of times.

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The Power Cleaner contains chlorine and should be sprayed evenly onto the dry cloth
Photo: YACHT/H. Schmidt
After pre-cleaning, sparks and algae are tackled. The Power Cleaner may need to be used several times, but it also removes dirt that is deeply embedded in the fabric

Tarpaulin fabrics are generally dyed to be UV-resistant, so there is no need to worry too much about fading. You only need to be careful with light beige cotton blend fabrics.

According to Gerhard Macht from the mould protection service, ferrous deposits can form in the fabric during the production process. This is why they tend to discolour when using the mould stain remover Tentoclean. He therefore recommends pre-treatment with his fibre protection agent. According to him, other colours or pure synthetic fibre cloths are not critical.

Macht also cites reasons for the increasing algae and mould stain problems: "The stricter biocide guidelines prevent the effective finishing of the fabrics." If the storage conditions are not ideal, the material already starts to develop mould at the Persenningbauer Spak. Mould fungi feel at home from 60 percent moisture - a level that is quickly reached with tarpaulins and sprayhoods in spring and late summer. The strong temperature fluctuations then cause a lot of condensation.

Impregnation is important

The fact that the tarpaulin becomes waterproof thanks to good waterproofing is almost a side effect. It is at least as important to prevent the fabric from becoming damp so that it can dry quickly. The water protection also has a grease-repellent effect. This makes the fabric easier to clean, and algae and mould find fewer nutrients.

The impregnation can be sprayed, brushed or rolled on. It is best to start on the inside
Photo: YACHT/H. Schmidt
The impregnation makes the cloth waterproof again. It also dries faster, which protects against premature re-infestation by algae and spores.

High-quality impregnation can also withstand washing without any problems. However, the mechanical stress caused by folding the fabric, hail and heavy rain will wear it out, so the protection must be renewed every two to three years. The tarpaulin should lie flat and always be treated on both sides. It is also crucial for success that there are no cleaning agent residues in the fabric and that the specified drying times are observed.

Maintain the discs too

Sprayhood windscreens are sensitive. Water stains and dirt can be gently removed with <a href="http://www.vuplex.de" target="_blank" rel="noopener noreferrer nofollow">Vuplex</a>. Spray on and polish with a clean microfibre cloth to remove even light scratches | YACHT/H.  SchmidtSprayhood windscreens are sensitive. Water stains and dirt can be gently removed with Vuplex. Spray on and polish with a clean microfibre cloth to remove even light scratches | YACHT/H. Schmidt

Note the time required

Although the whole process takes less than four weeks, the time required should not be underestimated. The necessary drying times between pre-cleaning and algae control and before impregnation alone will keep you busy for a good two days. The cleaning agents required for the sprayhood and tarpaulin cost around 100 euros.


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Hauke Schmidt

Hauke Schmidt

Test & Technology editor

Hauke Schmidt was born in Hanau, Hesse, in 1974, but moved to the coast at the age of an Opti and grew up sailing dinghies and tall ships. School and semester breaks were used for extensive Baltic Sea cruises. During and after his oceanography studies in Kiel, he took part in various international research trips to tropical and polar regions. The focus was on ocean currents and their influence on climate change. Eventually he was drawn back to his home coast and to YACHT. He completed a traineeship there and has been working as an editor in the Test & Technology department since 2009. His core tasks include equipment and boat testing, as well as practical topics relating to electronics, seamanship and refits. As a passionate DIY enthusiast, he loves to spend his summers on the water with his family and winters working on his boat

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