A mild bleach solution removes stubborn mildew from outdoor furniture fabrics. Mix 1 tablespoon of bleach into a pint of warm water in a bucket. Dip a sponge into the solution and soak the mildewed areas, leaving the furniture to sit in the sun on a nonhumid day for 15 minutes.asic Borax Cleaner. A borax solution removes mildew from affected fabrics and works best when the fabric is allowed to dry outdoors on a sunny, nonhumid day. Brushing the mildew spots off first with a broom or nylon brush outdoors removes some of the residue.