we irrigate our lawn with well water with a high iron content. when it's windy sometime it sprays on the siding. this has resulted in very bad stain marks on the vinyl. after doing some research online, i found a product called Rustaid Outdoors from the makers of damp rid. they claim you only have to spray this on with a garden sprayer and it just dissolves before your eyes. i thought "ya right!". boy was i wrong. this stuff is GREAT and it does dissolve as they claim. had to spray it twice and in just a couple of areas had to lightly scrub with a soft brush then rinse with water, but it only took minutes for a job i thought might take hours. i bought a gallon for 10 bucks and only used half of it. the only problem was finding it. according to their website, many stores carry it, but after a dozen calls, i found no one who stocked it. i ended up having my local ace store order it in. i rarely take the time to write a review for any product, but this worked so well i wanted to let others here know about it. gardenweb is such a wonderful forum and i've learn alot from all the contributors over the years, so i'm putting in my two cents worth.