"What chemical can I use to turn a copper pipe verdigris?"

A. Hi, Randy. If you are a homeowner wanting to do this for the first time for a window in your home, and wishing only to spend limited time on it, please search the site and you will see some suggestions of chemicals you can try like vinegar and salt or Muriatic Acid [affil link], but I wouldn't expect professional looking results without a significant effort. An alternative would be to do a vertigris finish with something like Jax Patina [affil link].

If you are interested in beautiful verdigris finishes and patinas of other colors, directed more towards the artist than a home handyman, please try to get access to a copy of the book listed near the top of this page. Good luck with the project!