Mildew is a type of fungus that grows in damp conditions. Mildew can appear on sails after a period of storage: However, the presence of mildew does not seem to affect the structural stability or performance of sails. Mildew gets its nourishment from tiny compounds found in the water, air and other organic matter. Roller headsails appear to be a breeding ground for mildew because they are stored rolled up, which can be a trap for rainwater. Cleaning mildew from sails is a relatively straight forward procedure.
Put on your rubber gloves and safety goggles. Wear your decorating mask before handling the sails to prevent you from breathing in any mildew spores.
Fill the large tub with water until it's 3/4 full. Add 1/2 a cup of chlorine bleach per gallon of water added to the tub.
Fully immerse sails in the tub bit-by-bit, using your body weight to force out any air pockets as you go. Do not try to immerse the sails tightly folded or rolled. Light folding is fine if they are too big for the tub, but try to open them up as much as you can.
Place heavy bricks on top of the sails in the tub to prevent the sails from floating up and sticking out of the water. Ensure that all corners are covered and all of the fabric is submerged.
Soak the sails for a few days. Three days should be sufficient to kill and remove all of the mildew from the sails.
Wear your gloves, goggles and mask again. Remove the chlorine solution from the tub and add fresh water to the tub. Fill the tub and use your hands to push and pull the sails in the water allowing it to soak the sails and rinse off the chlorine. Repeat this process two or three times.
Take the sails out of the tub. Hang them up outside and hose them down with fresh water from your garden hose. Thoroughly soak them and keep spraying until the smell of the chlorine has completely gone. Allow the sails to hang dry.
Store your sails only when they are completely dry. Do not put sails into storage that are still wet or damp as this will attract mildew. Consider using an anti-mildew treatment on your sails.
It is thought that laminated sails are an ideal breeding ground for mildew. Store them in a dry area and do not fold or roll them.