Suitability for Use
Assuming there is no oil, lacquer, grease or wax over the green patina, the Jax Instant Brass and Copper Cleaner will do the job.
We would wash the art with Dawn dishwashing liquid to remove surface dirt, outdoor grime and fingerprints, and rinse it well with water. While it is still wet, apply Jax Green Patina with a stiff bristle brush. Allow to dry over-night. You can re-apply the next day if necessary.
Unfortunately we do not have photos to show at this time. A gallery of pictures will soon be available. Until then, we can tell you the Jax Brown-Black is a very versatile product and will allow you to replicate a wide range of browns (to black). Also, since you are working on a roof, from the vantage point of the ground the difference between the brown and the brown-black will be negligible.
The Jax Green Patina can be used on copper intended for exterior applications with no problems at all. If you are using virgin copper we would either: install the sign outdoors and let it sit for a while or darken the copper a bit with Jax Brown-Black and then apply the Jax Green Patina over the Brown-Black for a more authentic look. Regardless, do not apply the Jax Green Patina on hot copper (it will evaporate and do nothing) or on a day when it will rain on the sign (too much patina will just wash off on that first day).
All Jax blackeners, darkeners and patinas can be removed with steel wool or Scotch-Brite. You can apply the Green on top of the black you have now for a more authentic finish (the copper should be cleaned of grime (nature), and have no wax, oil, lacquer or grease on it. Or you can remove the black and apply the Green directly to the bare copper (more work, try it with the black first to see if you like it). We would use Dawn to clean everything first. We would not seal it (we think it causes more headaches later on.)
The desired effect should be achieved in less than 30 seconds. Remove the items from the solution as soon as the desired color has been achieved. Wash thoroughly with water and dry. If you are using the products on iron or steel, remember that the Jax Blackeners are NOT rust preventatives and the items must be washed and dried (and possibly waxed or lacquered) in order to avoid rust.