Patinated copper: surfaces that hold their own in a building.

Copper reacts with oxygen in the air to form copper oxide. This first layer darkens the metal from bright red gold through brown to almost black. Only over many years, under the influence of moisture and carbon dioxide, do basic copper carbonates form: the green patina known from copper roofs. Patination reproduces this process under controlled conditions in the workshop, so that the desired colour is there from day one.

Yes. Because the colour comes from a chemical reaction of the material and the process is guided by hand, every surface turns out slightly differently. The colour character is reproducible, the exact marking is not. For large continuous areas this should be considered early in the design.

A very long time. Depending on location and weather, roughly ten to thirty years pass before the green carbonate layer has formed across the whole surface. Near the coast and in cities it happens faster, in dry air more slowly.

Along the way the surface passes through every intermediate stage: red gold, brown, dark brown, anthracite. Anyone who wants the final state from the start cannot avoid having the surface patinated in the workshop. That is exactly what the process is for.

Not with all of them, and this is a genuine design question. Copper is more noble than aluminium, zinc and galvanised steel. If these metals come into direct contact in the presence of moisture, the less noble metal is attacked and erodes. Engineers call this galvanic corrosion.

The same applies to run-off water: copper does not belong above zinc or aluminium components, because the water carries dissolved copper compounds with it.

It can be solved with separating, non-conductive layers or a substructure in stainless steel. What matters is that it is considered early.

It protects it. The carbonate layer bonds firmly to the metal and slows further attack by air and moisture. Unlike rust on steel, which flakes off and carries the damage ever deeper, patina acts as a barrier.

This is why copper roofs last for centuries without the substance beneath them being lost.

Yes, and this belongs in the detailed design early on. Rainwater running over an unsealed copper surface carries dissolved copper compounds with it. Where it meets pale materials such as natural stone, fair-faced concrete or render, greenish veils can appear over time.

It is avoided through standard detailing: controlled water routing, drip edges and gutters, so that the water does not run freely across sensitive surfaces. Considered in the design, the matter is settled.

The two are constantly confused, but they are different substances.

Patina consists of basic copper carbonates. It forms through air, moisture and carbon dioxide, adheres firmly and is harmless. This is the green known from roofs.

Verdigris is copper acetate and forms through acetic acid. It is toxic, practically does not occur on buildings and has nothing to do with the patina on a façade.

That depends on the finish chosen. Left natural, the surface keeps reacting with its surroundings. Waxed, the process is slowed. Lacquered, the reaction is stopped completely.

The three finishes compared