Decks, Patios, Porches and Docks - Black Vertical Lines on Cedar Railings

I have frequent, black, vertical lines on my cedar railings. I'm trying to understand what I need to do to remove these lines. The deck is only a year and a half old and the railing were treated immediately upon installation with an applicaiton of Cabot Problem Solver Wood Cleaner and one coat of Cabot Clear Solution, with a Cedar finish. I don't want to do any further damage to the wood, so I'm curious if I'd be better off sanding off these black lines, or treat it? Thanks.

What type fasteners were used to attach the railings? If not stainless steel or powder coated fasteners, you have rust and will have rust, so sanding may not "fix" it until you change out the fasteners. It would help us, too if you could post a couple of pix on a site such as photobucket.com and copy/paste the HTML code to your reply post. That way we can see what you see.

I have attached a link that shows the black, streaky lines. I believe the lines may be a form of mildew, as I took a little bleach to one section and the lines went away. I was planning on treating this shortly with some Cabot problem solver.

Pictures by cgarrettharc - Photobucket (http://s615.photobucket.com/albums/tt232/cgarrettharc/)

Bleach/water solution is good for removing/killing mildew. it should never be stronger than 50% and must be rinsed well. Bleach can destroy wood fibers if used inccorectly!

You might consider adding extra mildewcide to the coating you use.