Did some.kite maintenance today on a kite that I just repaired the trailing.edge, the canopy had a large dark rust stain on it. Looked on the net and found that lemon juice and salt mixed together removes oxidsed iron (rust).
Cut a lemon in half and smeared it on the stains and then sprinkled salt on and rubbed it in a little and left it in the sun for a while. Came back 30 min later and.it looked substantially lighter, reapplied another 2 times and it.is virtually gone.