Mould stains and algae are almost impossible to avoid on sprayhoods and tarpaulins on board. How to get your weather protection clean and waterproof again, and delay the next outbreak.
Green seams, black specks and stains on the inside – what at first glance looks like a cosmetic issue quickly turns into a serious threat to the sprayhood and cover. Our sprayhood, which is only four years old, is already showing clear signs of algae and mildew stains. The flybridge cover has been hit even harder: not only has the material turned green, but it has also become water-permeable. The fabric soaks up rainwater and dries only slowly – a vicious circle that accelerates mould growth and algae infestation.
The problem is of our own making, explains Gerhard Macht of MTS Schimmelschutzservice: “The stricter biocidal product regulations prevent fabrics from being effectively treated.” Modern tarpaulin materials arrive from the manufacturer with virtually no protection – sometimes already showing the first signs of mould. Added to this are the conditions on board: mould thrives at humidity levels of 60 per cent or higher, a figure that is regularly reached in spring and late summer. The sharp fluctuations in temperature lead to plenty of condensation on surfaces.
What you should bear in mind when cleaning the tarpaulin
Green soap and vigorous scrubbing are of little help. It’s tempting to reach for a diluted sanitiser – after all, the sodium hypochlorite it contains reliably removes organic dirt. However, this chlorine compound has an insidious side effect: it attacks the cotton covering on the seams. These natural fibres normally ensure the seams are watertight because they swell when wet. However, the aggressive chemical drastically shortens their lifespan, so it’s better to use a tent or tarpaulin cleaner. Professional cleaning is convenient and not expensive, but it’s not for those who leave things to the last minute.
Sail and cover makers work with specialist industrial cleaning firms that charge by weight. For our sprayhood, which weighs around 3.5 kilograms, the Dutch provider Zonklaar would charge around 270 euros; the boom cover would cost a further 210 euros. The time factor is even more significant: the weather protection can be away for up to four weeks – which isn’t ideal in the middle of the season.
The alternative is to do it yourself. There are various tarpaulin cleaners available on the market, for example from specialist firms such as Ultramar in the Netherlands or the German company MTS Schimmelschutzservice. There are also household cleaners and products from other suppliers. In our test, we tried out the Ultramar products as well as those from MTS on our tarpaulins. In addition, we tested a selection of other cleaners on a worn-out sun awning. The Ultramar cleaners delivered good results, but required a considerable amount of effort. Tentoclean from Schimmelschutzservice proved far more effective: the mould stains on our flybridge cover disappeared almost completely in no time at all. The catch: as the product contains chlorine, it gives off a strong odour and should only be used outdoors.
Pre-cleaning
Impregnation
Once the fabric has been cleaned, it is time for waterproofing. Many people see this merely as a means of making the fabric waterproof. In fact, the key factor is how quickly the fabric dries: a well-waterproofed fabric does not absorb water and can dry quickly after rain.
Waterproofing doesn’t last forever. Mechanical stress caused by creases, hail and heavy rain wears down the protection. A fresh coat needs to be applied every two to three years. For our already well-worn tarpaulin, we chose Easy-Top from Schimmelschutzservice. This ensured that water still rolled off it even at the end of the season.
Strict adherence to the manufacturer’s instructions is crucial to success – both when removing mildew stains and when applying a water-repellent treatment. A particularly critical consideration is whether the surface should be dry or damp for the respective step. If used incorrectly, the cleaner loses much of its effectiveness. With waterproofing, the consequences can be even more serious: water-based products work even on damp surfaces, whereas others form unsightly stains that are almost impossible to remove.
Effectively renewing weather protection
The waterproofing treatment makes the cloth waterproof again – it dries more quickly, which helps prevent the growth of algae.
Tackling mould stains
To remove dirt that has penetrated deep into the fabric, it may be necessary to apply the cleaner several times.
Summary of the tarpaulin cleaning process
Although the whole process doesn’t take four weeks, as it does with a professional clean, the time involved should not be underestimated. The drying times required between pre-cleaning, algae treatment and waterproofing alone will keep you busy for a good two days. The cleaning products needed for the sprayhood and tarpaulins cost around 100 euros, which is about a fifth of the cost of a professional clean. If you take great care, the tarpaulins will look as good as new after washing. Here you can find the tarpaulin cleaners featured in the BOOTE test.
Hauke Schmidt
Test & Technology editor
