Treat your canvas right and it should last for years.
Keeping a boat shipshape might seem like a mostly aesthetic endeavor, but there is something to be said for the old expression "a clean boat is a happy boat." Conversely, an unclean boat can also be a "spiteful" boat. Most marine fasteners, fittings, and gadgets are designed to withstand the elements, but if left unchecked, an accumulation of dust, dirt, and standing water can end up compromising a lot more than a vessel's curb appeal. Many boaters turn to canvas covers and tops to protect their pride and joy from rain, dirt, and the occasional bird bombing.
While a canvas can spare you the misery of taking a rag to the avian poop deck, it demands its own share of TLC. Plus, if not cared for properly, canvas can lose its ability to repel water, meaning that instead of protecting your boat, you'll be subjecting it to a consistent trickle of guano-steeped rainwater. Luckily, keeping canvas surfaces clean and in good shape is easier than you may think.
Cleaning canvas is easy, but it isn't foolproof. Going at it with a pressure washer or some household cleaning detergent might yield promising results, but doing so can actually damage the material. Your best bet is to start by gently removing loose dirt and bird droppings with a bench brush or a dry rag. It's a good idea to remove bird droppings or bug splatters as soon as you notice them as they can leave formidable stains if left to sit. In some cases, a slightly damp rag will be needed. But don't apply too much brute force or it can work dirt into the material.
To get rid of deeper stains, you'll have to employ some mild soap like Woolite or Dawn. Keep in mind that many detergents can break down the canvas's water- and UV-resistant coatings, so it's always a good idea to check the manufacturer's recommended cleaning solution. You can also find purpose-built canvas cleaners from companies like Starbrite.
Directions vary slightly between products, but in general, start by spraying down the canvas with fresh water. Pressure washer jets are powerful enough to damage canvas fibers, so using a regular garden hose is the best move. The goal here is to fully soak the material rather than try to remove dirt with water pressure. Make sure to thoroughly dampen seams where the canvas is doubled up. Then gently apply the soap with a soft bristle brush. After working it into the fabric, allow it to sit for several minutes to help break down the grime. Once it's had time to soak in, go at it again (gently) with the brush, then rinse the canvas thoroughly. You might have to repeat the process a few times to get ideal results.
Proper cleaning will help prolong the life of your canvas, but eventually, its protective coatings will deteriorate and it will need to be "reproofed." Canvas reproofers, like 303 Marine Fabric Guard, are solutions that restore water- and stain-resistant coatings, preventing mold growth and further staining or deterioration. Their application process is a little more demanding, but still pretty straightforward. Reproofers have to be applied after the canvas has been cleaned and allowed to dry, and many can't be exposed to direct sunlight during their curing process. That being said, all you'll need is a spray bottle of the stuff and a brush or roller for touching up hard-to-spray areas to get your canvas back in shape. Tip: Applying multiple light coats of reproofer tends to work better than applying one thick coat.
Good As New
With proper care and maintenance, there's no reason that your canvas won't last a very long time. And even though canvas care might take a little elbow grease, it certainly beats buying a new cover or scraping gull guano off your multifunction display. The one downside? If you invest enough time into it, you might end up wanting a cover to protect your boat cover!