We test 10 of the best canvas cleaners, plus two budget options, to find the best product to get your sprayhood and sail covers back to their best
As boats emerge from winter with algae-green sail covers and sprayhoods, the Yachting Monthly team go in search of the best canvas cleaners.
The start of the season is here. If your boat has lain neglected through the damp, cold winter, it may have taken on a tinge of green.
Nowhere more so than on her sprayhood and sail cover is the blight of mildew and algae to be seen, growing profusely on the damp and dirty surfaces. It’s time for a spring clean.
When we came to clean the neglected-looking canvas of a Sadler 32, we discovered a bewildering array of canvas cleaners on offer.
There are well over half a dozen canvas cleaners on the chandler’s shelves, as well as a few everyday household products that are rumoured to do the trick.
In testing the canvas cleaners, we were looking for cleaning power, ease of use, and ability to protect against future growth.
As we were playing around with chemicals, safety of use and their environmental impact was important.
Worryingly, some were marked as ‘extremely hazardous to skin, eyes, and marine life.’
A few canvas cleaners were clear winners, doing what they claimed within a short space of time.
Others are harder to judge, and the end of the new season will perhaps reveal more of their true performance.
For now, we based our test on the results obtained on the day.
How we tested to find the best canvas cleaners
The 10ft-long sail cover was removed from the boom for ease.
The algae had grown heavily on the external underside of the sail cover, and less so on the drier upper sides.
We marked out 13 equal stripes across the width of the sail cover and labelled them, assigning one product to each strip.
Given the hazardous nature of some of these chemicals, we wore waterproofs, wellies and gloves, and spread a plastic sheet under the sail cover to stop leakage into the sea.
We then followed the instructions on the packaging as closely as possible, taking care to avoid contaminating adjacent sections.
Where scrubbing was prescribed, this was done for two minutes.
We then hung up the cover to dry and compared before-and-after photos to establish which had produced the best results.
Of the 13 spaces, three were control sections using common household products: non-biological washing powder, washing-up liquid and plain water.
Care for canvas
Before setting about cleaning, I sought the advice of some experts.
Gosport-based Tecsew specialise in canvas for boats, from cushions to cockpit tents.
Director John Bland shared his advice for caring for canvas:
- Clean your canvas in situ. It’ll be an easier job so is more likely to happen. Even just a quick brush with some water will keep organic matter off and prevent growth.
- Avoid bleach-based products where possible as bleach weakens fibres, particularly stitching, shortening the life of your covers. Bleach is effective, however, as it kills the spores that cause mildew.
- Keep your canvas as dry as possible because mould and algae thrive on damp cloth. Turning your boat occasionally will help dry out both sides: the north side will have worse growth.
- On the hard, keep your boat away from trees: the shade, moisture and organic matter from plants and animals makes growth much worse.
- Canvas is permeable to prevent condensation and is not meant to be fully waterproof. Reproof it with acrylic canvas proofer once you’ve cleaned it to help water bead up and run off, and to stop dirt sticking.
- Don’t get these products on the vinyl windows as they will mark and damage them. If you do, wash off quickly.
Best canvas cleaners available right now
Euromeci Yachtline Muffa Net
The instructions for Muffa Net, having been translated, were vague.
Despite warnings of ‘extreme danger to eyes, skin and marine life’, the solution was to be sprayed straight from the bottle to saturate the fabric before leaving it to soak and then rinsing.
We disliked the idea of the bleach-based solution becoming airborne and getting into lungs and eyes, so proceeded with caution.
It removed a fair amount of dirt, though some scrubbing was required to lift the dirt off the canvas.
This was the strongest bleach solution we tested.
Active Ingredients: Sodium hypochlorite, active CI. <5%
Use: Spray on
Price as reviewed: £9.95
Renovo Boat Canvas Cleaner
After a quick brush off, the fabric was dampened with water before the neat Renovo Boat Canvas Cleaner was ‘painted’ on to the fabric using a brush.
We left the solution for 45 minutes before giving it a scrub and rinse.
It was a slightly more involved process than some of the other cleaners, requiring a few more stages.
Results were reasonable but seemed more reliant on the scrubbing we’d done, as dirt was still visible where the grooves in the pontoon had prevented the fabric from being properly scrubbed.
Active Ingredients: Non-ionic surfactant
Use: Brush on
Price as reviewed: £13.25
Starbrite Fabric Cleaner & Protectant with PTEF
Runner-up in our test
A simple cleaner to use, we sprayed this on, gave it a scrub and rinsed it off.
It is advertising as safe on marine fabrics and did not come with any major environmental warnings.
It is not bleach based and appeared to have much less impact on the colour of the canvas than other products.
It produced impressive results, even where the fabric was less well scrubbed.
Also laced with PTEF, or Teflon, it is designed to reduce UV damage and to repel dirt, although we weren’t able to test this claim.
Size: 1 litre
Active Ingredients: Non-ionic surfactants, EDTA, d-Limonene, PTEF
Use: Spray on
Price as reviewed: £20.95
Fabsil Universal Cleaner
Best on test
Designed to be used on any outdoor fabrics, including tents and garden furniture, this product was quick and easy to use.
It is also claimed to maintain water-repellancy but we were not able to test this accurately.
The canvas was first dampened, and then lightly scrubbed with the solution before being rinsed.
It was quickly apparent that the green mould was largely dealt with and the canvas was back to its original blue colour.
This was hands down the easiest to use and most effective of all the products.
Active Ingredients: <5% non-ionic surfactants, benzisothiazol
Use: Dilute 100ml in 5L of water
Price as reviewed: £8.95
Starbrite Sail & Canvas Cleaner
The cloth must be dampened before the solution is applied and given a light scrub and then a rinse.
It worked well, assisted by a bit of elbow grease.
On all but the most stained parts of the cover, it left the fabric a nice bright blue colour, so it was certainly doing something.
The addition of a natural cleaning agent such as Limonene seemed to be effective without being too harsh, although I can’t vouch for how kind it is to the fabric.
Active Ingredients: <5% non-ionic and cationic surfactants, EDTA, d-limonene
Use: Dilute 1:4 with water
Price as reviewed: £14.95
Iosso Mold & Mildew Stain Remover
Iosso is a non-chlorine based cleaner that claims to tackle stains as well as mold and mildew.
The instructions specified applying with a sponge, leaving to soak for 15 minutes before giving the canvas a light brush and rinsing.
Most of the green colouring was removed, but the darker stains were not removed.
It is possible that this cleaner is kinder to the fabric than other products, and may well be better at removing mildew if left to soak.
Active Ingredients: Pentasodium tipolyphosphate
Use: Dissolve 1 scoop per litre of water
Price as reviewed: £24.95
Wessex Sail Cleaner
Wessex Sail Cleaner is sprayed on and wiped clean and does not need rinsing.
It is a non-bleach-based product so is entirely safe on your stitching and is also biodegradable.
Having given a generous spray, this scented cleaner smells like school corridors the world over.
Having left it to soak for a few minutes, we gave it a wipe and a good amount of grime came away, but it needed a bit of a scrub for tougher stains and did not leave the fabric looking particularly clean.
This might be more effective on more waterproof sail cloth; it tackled the worst of the dirt, but did not wipe totally clean.
Active Ingredients: Tetrasodium ethylene diamine tetraacetate, alcohol ethoxylate
Use: Spray on
Price as reviewed: £11.95
Everbuild Sugar Soap
Best Budget Buy
A cleaning product readily available from DIY stores, sugar soap has been around for a long time as way of removing almost any kind of dirt from around the house.
It is inexpensive, and worked moderately well, as long as it was scrubbed well.
It was easy to apply using the spray bottle, or it could be dissolved in water and applied by sponge.
It rinsed out easily, although it does contain biocides, so potentially less good for the environment, should it get into the water.
Active Ingredients: Methyl isothiazolin, benzisothiazol, <5% non-ionic and anionic sufactants
Use: Spray on
Price as reviewed: £3.95
Yachticon Sail and Canvas Cleaner
A long-acting product, this is designed to be sponged on to the canvas as soaked for up to 12 hours or as long as possible, although it shouldn’t be allow to dry out.
It should then be brushed before being rinsed.
We were able to test this over a few hours, though not the full 12, and found that the canvas dried more quickly than expected.
It was a more involved process than other cleaners, and produced moderately good results.
Perhaps if it had been kept soaked for 12 hours, better results would have been achieved, but we questioned whether this was a practical expectation.
Active Ingredients: 5-15% soap, <5% non-ionic sufactants
Use: Dilute 50ml in 3.5 litres of water
Price as reviewed: £11.95
Brinton Patio Magic!
This is the product that the forums can’t recommend highly enough.
Not a marine-specific product, it is reputed to keep mould and growth away on all surfaces.
Once concern is the very clear warning that this product is extremely hazardous to marine life, skin and eyes.
If it is going to be applied, it should therefore be done on the hard.
It doesn’t contain bleach, however, so is safe on that count.
It is brushed or sprayed on to dry canvas and then left to dry for a latest five hours.
In our test, the algae turned from green to white and was clearly killed.
The canvas did not come clean, but in time it may have done.
Size: 2.5 litres
Active Ingredients: 5-15% benzalkonium chloride
Use: Dilute 1:4 with water
Price as reviewed: £7
Other household products
Washing-up liquid did not have as good a result as we had hoped.
When scrubbing the amount of lather produced was a nuisance and it took a huge amount of rinsing.
If you get grease on your canvaswork, this is probably a good bet but it was not successful against tougher mould stains.
Active Ingredients: 15-30% anionic surfactants, 5-15% non-ionic surfactants
Use: Mix with water
Price as reviewed: £1.31
Persil Non-Biological Washing Powder
Non-bio washing powder is meant to be used at higher temperatures, but on a pontoon we were limited to cold water.
Biological powder might work better.
It lathered up and removed the first layer of grime quickly.
Despite some extensive scrubbing, it didn’t do a great job with the underlying dirt.
Active Ingredients: 15-30% anionic surfactants, < 5% non-ionic surfactants, oxygen-based bleaching agents, soap
Use: Dissolve one scoop in 5 litres of water
Price as reviewed: £3.50
Perhaps unsurprisingly, water is a key element for most of the cleaning methods we tried.
A good old-fashioned spray-down, scrub and rinse coupled with a stiff brush did a good job of tackling the surface mould and algae.
Good enough for government work, although it didn’t do much to tackle the deeper stains.
It shows that a regular wash-down and brush helps keep things in good condition.
Which were the best canvas cleaners on test?
There is a wide range of canvas cleaners on the market.
In general, targeted products that are designed for the job perform better than generic cleaning products, although we were surprised by how well sugar soap performed.
At under £4 per bottle, Everbuild Sugar Soap was our best budget buy.
A number of the products contained bleach, which kills the mildew and algae spores but risks weakening stitching, so we would prefer not to use bleach-based cleaners on canvas.
Most products contained some form of surfactants and also biocides.
Clearly these need to be kept out of the water and off the skin where possible, particularly the more aggressive products such as Patio Magic, though this is effective over a long period of time.
Fabsil Universal Cleaner worked quickly, easily and effectively with a minimum amount of fuss, without visibly fading or harming the canvas at all. It was also fairly inexpensive and as a result of this, it became our favourite product.
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With a spray bottle it was easy to use, left the canvas clean without having to scrub too hard, and had the added benefit of protecting the fabric in one product.
Whatever product you use, it is definitely worth reproofing the fabric.
It won’t make it totally waterproof, but it’ll help keep your canvas in the best possible condition throughout the entire season.