Evolution. Rust, Patina and corrosion
The finishes are instant and permanent. When applied to your metal fabrication they can be guaranteed for an external environment for 25-years and internally for even longer.
There is no need to wait for the patination to evolve and risk it not being what you want.
No need to use expensive base metals such as copper, zinc, Corten, brass or bronze. Evolution finishes can be applied to lightweight aluminium or plain steel to achieve an expensive look.
All finishes are easy to maintain - just wash with water. There is not toxic run-off and staining of adjacent mateials, ground, brickwork etc.