Outdoor Cushion Mildew Remover
A powerful oxygen bleach soak that lifts mildew stains from outdoor cushion fabric
Ingredients
- 2 gallons Warm water
- 1/4 cup Sodium percarbonate (sold as oxygen bleach or OxiClean Free)
- 1 tbsp Liquid castile soap
- 1/2 cup White vinegar (for a separate pre-treatment spray)
- 2 tbsp Baking soda (for scrubbing paste on stubborn spots)
- 1/4 cup Hydrogen peroxide (3%) (for spot treatment of dark mildew stains)
Steps
- Remove cushion covers if possible. Brush off loose dirt, leaves, and debris from both sides.
- For dark mildew spots, spray undiluted white vinegar directly onto the stains and let it sit for 10 minutes as a pre-treatment.
- Mix the sodium percarbonate into 2 gallons of warm water in a large tub or plastic bin, stirring until dissolved.
- Add the castile soap and stir gently to combine.
- Submerge the cushions or cushion covers in the solution, pressing down to ensure they are fully saturated. Soak for 30 minutes.
- For stubborn spots, make a paste with baking soda and a splash of hydrogen peroxide. Apply to the stain, let sit for 10 minutes, then scrub with a soft brush.
- Remove the cushions from the soak and scrub both sides with a soft-bristle brush, working in circular motions.
- Rinse thoroughly with a garden hose until the water runs clear and no soap remains.
Why It Works
Mildew thrives in the damp, shaded conditions where outdoor cushions are stored, forming dark surface colonies that root into fabric fibers. Sodium percarbonate releases hydrogen peroxide and sodium carbonate when dissolved, creating an alkaline oxidizing solution. The hydrogen peroxide penetrates fabric fibers and breaks the chemical bonds in melanin-like pigments that give mildew stains their dark color. The sodium carbonate raises the pH, which emulsifies the oils and organic matter that mildew feeds on. The vinegar pre-treatment works by creating an acidic environment that kills surface mildew spores before the main soak, while the baking soda paste provides localized mechanical abrasion for deeply embedded stains.
Tips
- Prevent mildew by storing cushions upright so air circulates around all sides, or bring them inside during extended rain.
- Clean outdoor cushions at the start and end of each outdoor season for best results.
- Sunlight is a natural mildew killer. After cleaning, dry cushions in direct sun for several hours.
- For Sunbrella and other solution-dyed fabrics, you can safely increase the sodium percarbonate to 1/3 cup.
- Never put foam cushion inserts in a washing machine. The agitation can tear the foam.