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Awnings do require regular cleaning, but mildew demands a different kind of cleaning solution and more elbow grease. Mildew is a type of fungus that's similar to mold. On an awning, it will likely appear as gray or white spots, and will look like a powder. You can simply use a regular cleaner if your awning doesn't have mildew. To get the best results from your cleaning efforts, start by hosing down the awing so it's completely wet. This will make the cleaning solution easier to spread, and the mildew easier to remove. To remove mildew from a canvas awning, you'll need a cleaning solution made with 1 cup (237 ml) bleach, cup (59 ml) of mild liquid soap, and 1 gallon (3.8 L) of cool water. If you need more cleaning solution, simply double or triple all the quantities. Mild liquid soaps include laundry soaps that are designed for sensitive skin, babies, or delicate fabrics. Do not use chlorine bleach on canvas, as this can damage the fabric. For colored awnings, use a color safe bleach. It's also a good idea to test a patch of the cleaning solution on an inconspicuous area to test for color fastness. Place some cleaning solution on a small patch of the top side of the awning and let it sit for 20 minutes before rinsing and checking for discoloration. Dip the clean cloth into the cleaning solution and spread the cleaner all over the awning. Re-dip the cloth as necessary so that cleaning solution reaches every inch of the fabric, otherwise you might miss some of the mildew. Once the entire surface of the awning has been soaked with cleaner, let it sit for about 15 minutes. This will give the cleaner time to soak into the fabric and kill the mildew. When the cleaning solution has had time to soak in, take the soft-bristled brush and scrub the top side of the fabric. Use a vigorous circular motion to generate suds. Go over every inch of the awning to scrub away all the mildew. If the cleaning solution starts to dry anywhere, re-soak the area before you scrub. After scrubbing mildew from the whole awning, rinse it well with clean water from the hose. Continue rinsing until all the soap and dirt have been washed off. You don't want to leave any bleach residue on the fabric, or it could cause early deterioration. If there's any mildew left on the awning, repeat the soaking and scrubbing steps until it's gone. Most awnings are designed to dry quickly after the rain, so it won't take your awning long to air dry. If you cleaned your awning in place, simply let it dry on the frame. If you removed your awning, hang it to dry on a line before reinstalling it. Never dry canvas awnings in a dryer, as they may shrink. When you bought your awning, it would have been treated with a water- and stain-resistant coating to protect it from water and discoloration. But scrubbing it with bleach will have removed this coating, so you'll need to reapply it. Look for a commercial-grade fabric guard that can be sprayed on. Once the awning is dry, spray the fabric guard onto the top side of the awning. Read and follow the manufacturer's instructions for specific instructions. Some awning warranties will be voided if you use silicone sprays, so make sure you check the conditions of your warranty. For smaller awnings that you removed to clean, return the awning to its frame once it's dry and after the water-resistant treatment has had time to dry.
Identify mildew on an awning. Hose down the awning. Mix your cleaning solution. Soak the awing in cleaning solution. Scrub the canvas. Rinse the awning. Allow the awning to air dry. Re-treat the awning. Return the awning to its frame.