Funny you should ask.. I just wrote something....
on this very subject that is going to be posted here and on the IG site. MY boat has grey streaks too!. They are NOT the same as black streaks and do not respond the same to cleaners. The grey streaks can be from chalk form gelcoat running down, salts (particularly in salt water environment) or from dusty air pollution. How about this I have these grey streaks only one one side of my boat (they show up on the dark green stripe) and this is the side nearest the dock (which is part of a main road). This does NOT come off with stuff that removes black streaks but does come off using microfiber cloth soaked in a little soapy water or (better) our Silkenseal that also shines the surface. You could also try other water-based products cleaner/polishes. By contrast, black streaks are due to exhaust soot in the air (oily) that gets into the wax (try dipping a candle in old engine oil!). As the previous poster said, black straks are (easily removed from conventional waxed surfaces by "black streak remover" (actually= wax remover, sometimes with a little added silicone and or wax for restoring the surface shine.) IG Superwaxed surfaces also get these streaks that are easily removed by some IG cleaner or more Swax of H SUperglaze (the glaze is all resin and is resistant to future stainining). If they are neglected and penetrate they get really deep (Swax is a THICK coating). Then you use undiluted S glow or equivalent or (accoriding to some) some polishing compound. Once removed, just reseal with fresh coating. There are also METALLIC streaks often seen under aluminum and stainless fittings, they are are different yet again and are treated differently too. Anyone interested further can get an e-mail from me with this subject. Thanks Jim W
