How to preserve patina vibrant colors & stop oxidationon copper wall ?

Seal with several coats of polyurethane. Marine grade varnish. Bullseye Sealcoat shellac. Automotive clearcoat lacquer

Geo: maybe a product like this would help

https://www.everbritecoatings.com/copper.htm

William has the answer. Seal it at the point you like the color. If inside use polyeureathane if out side Marine Varnish. Enjoy, I love copper.

Hello Geo,

You must lacquer the copper to prevent oxidation............

Apply a clear sealer to the copper so the copper doesn't oxidize by being in the elements.

Hi Geo, A day or two after the patina process, when the patina is finished and dry, seal it using a clear spray lacquer. Apply at least three light coats of lacquer on every patina surface of the metal, drying each coat thoroughly before applying the next coat. Hope this helps you

Hi! A clear sealer will keep it looking the way you want. You may have to repeat the sealer at a later date. Good luck and stay safe!

Here's a post that might help you - https://www.hunker.com/13416142/how-to-inhibit-or-stop-the-copper-patina-process

I'd use a sealant!

Try spraying a varnish or a scotch gard over it

Add a clear sealant. Probably a spray on version would be best.