How To Clean Mildew In Canvas, Non-Skid and Other Areas On Your Boat

dirty sailboatThis week’s question is about mildew. Boat owners email me every year around this time asking how to clean mildew out of their canvas, non-skid and teak decks and how to keep it from coming back so soon.

As I’ve always said, dirt and mildew is the one constant in boating. It doesn’t matter if you have a six million dollar yacht, an old wooden boat or a new sailboat, mildew doesn’t judge! It will find your boat, attach itself to your canvas, teak decks, window sills and non-skid, and will quietly grow and multiply while you sleep. However, you can try to outsmart it and keep it from taking over with these simple tips on cleaning and removing mildew and then preventing it from coming back.

Keep in mind that there are two types of mildew or mold. Green mildew is what you’ll find growing in fabrics, such as canvas, vinyl edges and seams and on deck carpets. You’ll also see it on teak decks. Black mold is what you’ll find growing on vinyl cushions and in non-skid. If your non-skid has small black specks in it that don’t come out with just soap and water, that’s black mold. This article is discussing how to remove mold and mildew from exterior surfaces and materials. If you find any black mold growing inside the cabin of your boat, you can use many of these same tips and products, but the most important thing is to wear a respiratory mask when cleaning black mold from an enclosed space. It is known for causing respiratory problems and is not something you want to breath in for any length of time.

Mildew In Canvas

Canvas is one of those materials that mildew grows quickly in and if not removed in a timely manner, can become quite difficult to kill and remove down the road. It will grow rapidly around the edges and on the underside of the canvas enclosure of your cockpit or fly bridge. If not caught in time, it can also grow in the seams around the plastic windows and zippers. But you don’t need me to tell you all of the places where it can grow. You need to know how to get rid of it!

The first step is to gather the products you’ll need before you head down to your boat so you can kill the mildew and treat your canvas in one trip instead of having to come back several times and turning it into a larger project than it should be. Here is a list of the products you should have on hand:

  • Small scrub brush – sort of like a really large toothbrush, sold in the cleaning aisle at any grocery or variety store
  • Rubber gloves
  • Mildew cleaning/killing spray such as West Marine’s Pure Oceans mildew spray (biodegradable and less toxic) or Lysol or Tilex mildew cleaner
  • Boat washing gear (soft deck brush, boat soap, bucket, hose, nozzle)

When treating mildew in canvas, you need to be able to see exactly where the mildew is, so don’t wet down the canvas or wash it first, otherwise the canvas will darken from the water (unless it’s white) and you may not be able to see exactly where the mildew is. Take your mildew killing spray and spray it directly on all areas where you see mildew. If it’s on the underside of your canvas enclosure, spray the mildew killer on a deck brush or hand brush and then wipe the brush over that area. You may need to go over it a few times to remove all the mildew, but you don’t need to wipe it down afterwards, as it’s fine to leave some of the product in the canvas to help keep mildew at bay for a while.

If there is mildew around the edges of your canvas, spray those areas liberally with the mildew spray and let it sit in for a few minutes. Then take the small scrub brush and scrub those areas well, trying to get in the seams as best you can. You’ll know it’s working when you see green streaks running down the side of your boat from all of the mildew that you’re scrubbing out of the canvas. Hose the canvas off so you can see your progress and hit that area once more with the mildew spray and scrub brush. When done, wash your boat and rinse well so there are no green streaks still running down from the canvas.

Once you’ve removed the mildew from your canvas, you can use a product such as Mold Off to spray on your canvas in the areas where mildew grows. Spray it on and walk away and let the product do the work. It won’t harm your canvas to leave it on and will help keep mildew away for months at a time.

Mildew In Non-Skid

Black mold in non-skid will look like small black specks that aren’t coming out with soap and water. It’s actually quite simple to treat black mold in non-skid. Spray your mildew killing spray over the non-skid and then let it sit in for a couple of minutes. Then take your medium-grade bristle deck brush and run it over the non-skid, working the spray in. You don’t need to hose the decks at this time because you want to spread the mildew spray around, having it treat the black mold in its full strength before diluting it with water. It will suds up a little while you’re scrubbing the decks.

When finished, you’ll see the black specks disappear. If you want to be environmentally friendly, take some old towels and sop up the mildew spray on your decks before hosing them down. (If you choose this route, you may not need to hose them down at all.) Otherwise, hose them down well as to dilute the product running off your boat. Left to dry on your gel coat, the mildew spray can remove wax in that area and make it look streaky, so spend plenty of time rinsing the product off your boat.

Mildew On Vinyl Seats and Deck Carpets

You may find black mold on your white vinyl seats or green mildew growing around the edges or undersides of your vinyl cushions or on your deck carpets. The best way to remove the mildew on vinyl cushions is to spray it with the mildew spray and let it sit in for a few minutes. Then take the small scrub brush and scrub the edges or undersides clean. When done, wipe the area well with a rag, but don’t hose them down or they’ll be wet and susceptible to mildew all over again.

If there is black mildew on top of the vinyl seat cushion, spray with the mildew spray and let the bleach in the product do the work. Over the course of a few minutes, the black mildew will lighten up and eventually disappear. Wipe the cushion with a rag to remove the mildew product.

Treating green mildew in deck carpets is very easy. Simply spray the mildew spray over the area that’s green and walk away. Or you can sit there and watch the green mildew disappear, but it will take about 10 to 20 minutes. You don’t need to rinse or wipe it down because it’s alright to let the product stay on the deck carpets to prevent mildew from growing in that same area in the future. It may come back eventually, but you only need to repeat this process to remove it again. This is another area you can follow up with the Mold Off product to help keep mildew from growing back.

Mildew In Teak Decks

If there is green mildew growing on areas of your teak decks and you’re not planning on cleaning and brightening them with the two-part teak product, but instead just want to remove the mildew in the few places its growing (probably along the edges of the teak), you can do so with a soft scrub brush and some mildew spray. You don’t want to use a scrub brush that is too stiff, so if you rub it on your face or the back of your hand and it feels too scratchy, then don’t use it on your teak.

Spray the areas where there is green mildew with the mildew spray. Let it soak in for a few minutes and then take the soft scrub brush and scrub it over the teak going against the grain. Because the brush is soft (it has to be for the good of the teak) and the mildew has grown into the grain of the wood, this process is going to take some time. You may need to scrub a section for several minutes to start seeing any difference or you may need to come back and treat this area a few more times over the course of a few weeks. When done scrubbing the mildew out of the teak, hose it down well to remove the bleach from the grain of the wood and rinse the green mildew streaks off your boat.

Cleaning and removing mildew from your boat can become an overwhelming project if you don’t stay on top of it, but if you treat it a little at a time and use the right products, you can keep it at bay long enough so it doesn’t get the chance to grow quickly and multiply to the point where you have to mow your canvas. Good luck and happy boating!

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