Waterproofing canvas with wood conditioner

Waterproof canvas with wood conditioner

By Dave Osmolski

Nearly every boat has some canvas to provide shade, act as a windbreak, and protect us from spray and rain. New canvas has a waterproof coating. Although the coating doesn’t actually seal the pores in the fabric, it does make the fabric hydrophobic, so water beads up and runs off.

Like nearly everything having to do with boats, the waterproof coating deteriorates with exposure to salt, sun and wind. Pretty soon, the canvas top is leaking onto your latest smartphone or all over your charts.

Most marine stores sell waterproofing compounds intended to restore the fabric’s ability to repel water. Like anything labelled “marine,” most of these products usually cost quite a bit more than we’d like to pay.

Some years ago, we used a clear wood conditioner to protect the boards on the walkway and dock at our place in Florida. We applied the water-based product with a roller and brush and cleaned the tools with soap and water.

After the conditioner dried, I noticed how the deck repelled rain. The water beaded and rolled off. I had at least a quart of this conditioner left, so I filled a spray bottle with the leftovers and used it to waterproof my canvas Bimini top.

First I washed the canvas with soap and water, rinsed it well and let it dry in the sun for a day. Then I sprayed the top until the canvas was thoroughly wet and let it dry in the sun. With the next rainstorm, the water beaded up and rolled off same as when the top was new. It held up as well as the original waterproofing.

Before starting this project, you should test the waterproofing solution on a small, obscure area of your canvas, as the coating could change the color of your canvas. If overspray gets on gel coat, metal, wood or clear vinyl windows, the product will dry and be nearly impossible to remove. If you are waterproofing canvas adjacent to clear vinyl or any other surface you don’t want to be sprayed, mask those surfaces with sturdy, non-absorbent paper held on with waterproof masking tape.

Now you won’t have a partially full container of deck conditioner in your garage, and your canvas will repel rain and spray as well as it did when new.


D/Lt/C David H. Osmolski, SN, of Charlotte Power Squadron, has been repairing boats since high school when his first boat, a canvas-covered canoe with cedar ribs, leaked in gallons per minute and required constant repair.

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