Try bleach. Just wipe on with a cotton cloth. It takes the shine off and dulls it.

Don't know how well this works for straight copper, but I made a penny gazing globe by siliconing pennies onto a bowling ball. I made up a strong solution of Peter's Plant food in water and sprayed it on the ball and the pennies developed that great copper verdigris color in no time. I initially thought the color would wash off when it rained, but that bowling ball was outside all last year in all the rain we had and the color is still there. For copper pipe, you might have a problem with getting the fertilizer solution to stay on the pipe long enough to get the color to develop, but if you could lay the pieces of copper in a tub and let it soak in the solution for a while, that might help. It would probably also help to wipe down the pipe with some cleaner to remove any old oxidized finish so that the fertilizer solution would have a bare "virgin" copper surface to work on.

Much of untreated copper is very easy to stain.
But if it has been lacquered, you will need to remove it with Lacquer Thinner which is very toxic.

This might be a messy and expensive way, but have you ever seen pennies that have been sitting in a spilled puddle of Coca Cola? L.

I have heard that plain yogurt spread on the copper and left in place for awhile will create the proper conditions. ???

Salt Water. Works great on ships bells... and they are brass!

Vinegar. Cheap, works good, and you don't have to collect it from the potty.

Hey Dixie, say you has some 3/4" copper pipes, 4' long .. how would you treat them ? Wet them with vineagar and wrap em in plastic for a day or so ?

Easy way to get a great patina on copper:
Rub all the finish off with steel wool, mix vinegar and salt in a squiter bottle. Squirt all the copper. Be careful where you lean your project to patina it, as this mix will kill all green plants it comes in contact with.
Cool patina overnight!!!

Here is a chart that shows the progress over the years if you don't do anything, and if you don't live in an arid climate. Some of my copper tuteurs are about five years old and they are getting close to the color given for four years. I have a dry summer climate, but I do irrigate, so I guess that makes up for a lot.

I once tried an earlier suggestion of spraying Miracid (now called Miracle Grow for Acid Plants, I think). It did not seem to do anything. I'd love to hurry the process along, but my copper structures have plants growing on or through them, so unless the treatment is pretty benign, I'll just let nature take its course.

Paula

Here is a link that might be useful: Natural patina on copper

two words...

dog pee

Works like nothing else, of course you may not want to touch it any more!

Tracy! how do you collect it?

I do have 2 dawgs ..
[:o)
(:o)

After reading all the above copper patina recipes, I made up my own concoction using sawdust from my stallion's bedding that was well saturated in strong urine. I scooped the soaked sawdust bedding into a large plastic coffee can and added a good measure of salt and mixed well. I buried a test piece of copper into the mixture and covered it with the coffee can lid. (I suggest wearing latex surgical gloves as this stuff is really strong and after all it IS horse urine!)
In one hour the piece was a beautiful speckled turquoise. After three hours the entire piece was vivid turquoise. I removed the copper, it let dry in the sun, rinsed it in water, let it dry again and spayed it with matte Krylon clear craft sealer. This worked well for my embossed copper project.
(rinsing the copper before letting it sit in the sun caused some of the patina to chip away, drying first allowed the patina to adhere to the piece)