Easy DIY
* Warm Water
* Table Salt
* Vinegar (Any kind should do)
After copper is cleaned wash off with water to remove vinegar.
Also to give copper a patina. Brush new/ clean copper with steel wool then use a cheap hand pump sprayer to cover the copper.

































I recently removed parkerizing from an old shotgun (steel) using Distilled Vinegar. I just left the main parts soak overnight, dumped the smelly vinegar, gave them a soak in water to remove the vinegar, and then promptly moved the pieces into a pre-heated oven (250 degrees) to dry before rust had time to settle.