Sail Maintenance
I always refer to Jeremy Howard-Williams' "The care and repair of sails" published by SAIL BOOKS, INC. in 1976 ISBN:0-914814-06-0. The book is out of print but there are still copies floating around. To remove rust stains (but NOT on spinnakers), Jeremy recommends either immersing in a solution of 1 ounce of 5% oxalic acid (poisonous) per pint of hot water or a warm solution of 2 parts concentrated Hydrochloric Acid to 100 parts water. Do NOT get either of these solutions on galvanized luff wires, bronze grommets/hanks, iron or copper! Rinse the sail thoroughly with fresh water after treatment. Before this extreme procedure on rust, I would try the more benign baking soda and/or tooth paste or Magica. Dishwashing liquid is good for general washing. It's neither acid nor alkali so it won't sensitize the sail cloth to UV rays. Laundry detergent and plain Clorox (1 cup per half gallon of water) are good for removing heavier dirt and mildew (but Clorox is not recommended for nylon and Kelvar). Be sure to rinse thoroughly with fresh water after. If you know the specific sail material and stain composition I may be able to find more information. Here's an article on SailNet that may be helpful too...
