Water, sun, and other elements can ruin any outdoor fabric.
Mildew, in particular, is a threat to all outdoor cloth and is usually impossible to remove. Mildew normally occurs when items are allowed to get wet and dry slowly, again, and again. Since canvas is a fabric often found in outdoor usages such as tarps and tents, it’s a good idea to waterproof it to prevent mildew and dry-rot from occurring.
A small piece of canvas can be spread out onto a table and treated, but for a large piece, you might need to use the kitchen floor or your outside deck. There are several different ways to waterproof the canvas pieces. After smoothing them out, you can use wax for waterproofing. Blocks of wax can be rubbed onto the canvas, giving a thick coating of waterproofing, the natural way. One problem with wax is that it is difficult to get it into areas like corners and up against welt.
Shave a piece of wax to a point and use this to go under and over the welt and to push into corners. Another problem with wax is the way it feels. On furniture, wax can make it difficult to slide in and out of the chair. In addition, wax can sometimes change the appearance of the canvas fabric. Overall, the wax method is not the best choice for a reliable waterproofing treatment.
A better way to treat canvas is by using a spray that is available at camping stores or department stores. You might have to use several cans of the spray to treat the entire canvas piece, and each can is about $3 – $5. Each can will do approximately 200 to 250 square feet. These sprays coat the canvas with silicone to prevent the water from sticking or soaking in. Check the label to make sure that the formula is safe for fire retardant fabrics.
To apply, use gloves and spray in a well-ventilated, but not windy, area, and spray in rows to make it easier to see spots you might have missed. Make sure to do the edges well and even flip the edges up to cover the under the edge. After allowing plenty of drying time, re-treat the canvas for extra protection against rain damage. If you have lawn furniture, remove the cushions and after they are well cleaned and dry, treat them with the waterproofing spray. Be sure to do the underneath of the cushions as well as the top and the band.
For outdoor umbrellas, spray the upside of the umbrella and the underside as well. Repeat after drying. Although many people use water seal, meant for sealing wood products, to treat their canvas, this is not recommended by the manufacturers or by some who’ve tried it. The common complaint is that it does not allow the fabric to breathe and instead, causes the pores of the fabric to become clogged.
To make your own waterproofing formula, mix 8 fl oz of soya bean oil and 4 fl oz of turpentine. In a medium container, mix the two liquids well. This formula can be poured into a squirt bottle for easy application, or a sponge or cloth can be used to spread the liquid onto the canvas. You can also use a paintbrush or paint roller to apply the solution. The recipe for this waterproofing is for one application, but it is recommended that you let the first application dry and then re-apply. Use for awnings, patio furniture, boat covers, tarps, and tents. Store leftovers in a cool place and clearly label the container. Keep away from children and pets.
Yet another homemade waterproofing treatment requires you to dissolve a pound of laundry soap in two gallons of hot water, then stir until well dissolved. Soak the canvas in the mixture until well saturated. Squeeze out some excess liquid, then hang up or lay in the sun to dry. After drying completely, prepare the second dip for the canvas by dissolving a half-pound of alum in two gallons of hot water.
Soak the tent again and saturate it completely, leaving in the solution for at least a couple of hours. Squeeze out some excess and again set out to dry. When the canvas is fully treated, it is ready for outdoor use, but you might need to reapply after tremendous rains or after several weeks of usage.Soak the tent again