No finish necessary . Chemical layers interfere with the refraction (colours) . I have some sealed plexiglass frames to completely isolate the copper from oxygen , but haven't found them necessary after 6 years of careless storage , still vibrant as ever !.
Qualities of preservation :
No finish necessary . Chemical layers interfere with the refraction (colours) . I have some sealed plexiglass frames to completely isolate the copper from oxygen , but haven't found them necessary after 6 years of careless storage , still vibrant as ever !.