A metal surface is temporary.

Copper oxidises.  

Silver darkens.  

Bronze develops patina.  

Iron scales.  

Polished brass records every hand that touches it.

Contemporary fabrication often works against this behaviour: sealing, plating and coating surfaces until they become stable and repeatable.

Sometimes that precision is necessary.

At other times, allowing a material to react may tell us more.

Heat colouring, chemical patination, burnishing, oxidation and abrasion are not only finishes. They reveal different stages of the metal itself.

The surface can remain active after the designer has stopped working.