The case for copper, which we don't seal.
Why we ship a bare-metal cap, and what a year of Sydney air does to one.
Most copper bicycle parts are lacquered. The factory sprays a clear coat over the polish so the part stays bright in a showroom. The first chip happens during install. By month four the lacquer is failing in patches, and the copper underneath is darkening unevenly through the cracks.
We don't ship it sealed. The Top Cap you take home is bare C110, polished and degreased. That's it. By summer the rim darkens. By winter the centre takes on a slow brown. A year in, the patina is real, even, and yours.
The chemistry is straightforward. Copper hydroxycarbonate (Cu(OH)₂CO₃) forms whenever copper meets damp air and a trace of CO₂. It's stable, structural, and protects the metal underneath.
Some buyers don't want that. We have a Ti-Ox cap for them, and we'll happily wax the copper one before it ships. But the default is a part that earns its own colour.