Cleaning copper roofs

A. I have some experience with copper roofs. I assume someone has attempted to paint or (horrors!) tarred over your copper? Anything you use in a chemical line will require careful control of the runoff, and may leave the copper rather streaked or spotted unevenly. Good luck.

A. If a roof has not been painted I would suggest a stiff brush and a mildly acidic solution, there are a great number of things available that will work just fine provided you are willing to put in the elbow grease (ketchup is an unusual example, but it does work!) If you are looking for something that will not ruin the lawn or plants around the roof I suggest Kool-Aid or some other powdered drink mix, mix it with a bit of water, rub it on and scrub with a will, it's mildly acidic and non-toxic to the plants that you may have below the roof, the first rain will remove the sugary coating that is left when it dries (or just rinse with water). If you are intent on the copper staying bright I suggest looking for a clear spray on lacquer ⇨
(test it somewhere it won't be seen first).

Q. How well does the Kool-Aid work on the copper roof? I do not want bugs coming into the house.
Thank you.

Joan Detrick
- Phoenixvile, Pennsylvania U.S.A.
June 23, 2010
publicly reply to Joan Detrick

Hi Joan. I'm confident that Kool-Aid on your roof and in runoff into your garden won't attract bugs into your house.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
publicly reply to Ted Mooney

A. Bob,

I'm willing to bet that those rust streaks are caused by the nails holding your roof in place. Copper and alloys with a high quantity of copper in their mix usually oxidize into either a brown or green color.
I would suggest looking at the nails that were used on your roof, if they were steel I would suggest you leave it be. If they are something else (like copper), pressure wash the roof with a mild citric acid ⇦ on eBay or Amazon [affil links] (5%) solution.

A. If you've tried multiple products and found that they still weren't effective enough, you probably should change tack..

But if you are willing to try a two-step or three-step process instead of a one-step one, you could try lacquer thinner to remove any lacquer, followed by vinegar ⇦in bulk on eBay or Amazon [affil links] /salt/flour and that worked a little bit - say a few speckles of copper showing through after several hours of brushing/rinsing and repeat. Graduated to Comet and a Scotch Brite sponge and not much better. Got really brave and got out the 00 steel wool ⇦ on eBay or Amazon [affil links] and rubber gloves and gave it some elbow grease. A few more specks, but nowhere near shiny copper.

Next reached for the palm sander and fine sandpaper - wholly smokes did that do the trick. Sanded for a few hours and got into the corners with a wire brush wheel on my drill. Cleaned it all off with mineral spirits ⇦ on eBay or Amazon [affil links] and just gave it a coat of Minwax lacquer - looks like a brand new roof! I know the palm sander left a few circular sanding marks, but the roof is 7 foot from the ground, so unless I invite Shaq over for a BBQ, I don't have any worries.