Canvas: Material and Maintenance
Just like traditional wooden boats, traditional cotton canvas is waterproof. Cotton fibers swell when they get wet and so this seals the weave. But by now the cotton canvas has been substituted with either a vinyl-coated polyester or a woven acrylic, due to its high sensitivity to mildew and bird droppings.
The advantage of vinyl-coated fabric is the waterproof feature, but since it doesn't breathe, unless it is well ventilated, condensation wets the underside of the fabric and might lead to mildew. Neither are vinyl-coated fabrics to be recommended for enclosures such as sail covers or boat covers.
On the other hand, acrylic canvas is tight-woven, so it is waterproof and able to breathe at the same time; plus, it stands up to ultraviolet radiation, is not susceptible to mildew, resists staining. But unfortunately, besides a high cost, it gets its water repellence from chemical treatments and therefore might lose some of its efficiency. The result is a leaking fabric after a period of approximately 3 years, but other reasons expedite the failure of the coating too, such as scrubbing and detergents. But reproofing canvas is easy.
Treatment and canvas maintenance
For acrylic canvas a fluoropolymer-based product is the best treatment, since waterproofing treatments that contain silicone can damage the fabric, because it is likely to compromise the stain-resistance and will result in a patchy coverage. The fluoropolymer-based product is therefore compatible with the original finish and has the best results.
Petroleum-based products are likely to have the best impact on acrylic canvas, more than water-based ones. When cleaning the canvas you should follow a few important instructions:
1. Do not use hot water!
2. Do not use a harsh detergent!
3. Do not machine wash the canvas!
4. Never ever put it in a dryer!
5. Before using the canvas let it air dry completely!
6. A spirit-based treatment will damage plastic windows and zippers, so use it carefully! (e.g. protect the zippers with foil, etc.)
7. Before reinstalling the canvas let the treatment dry completely!
Generally speaking, the treatment should be repeated once a year, depending on the kind of use the fabric gets.