Herzog & de Meuron, as seen in their approach to brick at Tate Modern, build every project starting from a question about the material, not from a predefined form the material must simply adapt to. At the de Young Museum in San Francisco (2005), rebuilt after the previous building had been irreparably damaged by the 1989 Loma Prieta earthquake, this question finds one of the most elaborate answers in their entire body of work: an envelope entirely in copper, conceived from the outset not as a static cladding but as a material destined to transform visibly over the decades following construction.
A pattern derived from the park's light
The museum stands in Golden Gate Park, surrounded by tall trees whose canopy casts a constantly shifting play of light and shadow on the ground. Herzog & de Meuron translated this natural effect into a precise architectural pattern: photographs of backlit tree canopy were digitised, pixelated and enlarged, and the resulting pattern was translated into a combination of perforated holes (in six different diameters) and concave and convex embossed reliefs in the sheet metal (in eleven different depths), spread across nearly 7,000 copper panels, each individually designed so that no two are identical. The result, developed technically together with the specialist metal fabricator Zahner, is a facade that filters daylight into the museum's interior with a dynamic, shifting effect similar to sunlight filtering through leaves — an ornamental detail born from a specific environmental datum of the site, not from an abstract decorative repertoire.
Copper designed to disappear into the landscape
The choice of copper as a material was no accident: Herzog & de Meuron selected it explicitly in anticipation of its chromatic evolution over time. The bright orange copper of installation, over the building's first years of life, progressively darkened and eventually began to develop its characteristic green patina — a process that, for a building of this scale, is measured in decades, not years. The practice's stated intent was for the museum to chromatically merge, over time, with the vegetation of the Golden Gate Park that surrounds it: a building conceived to become part of the landscape precisely through the ageing of its own material, not in spite of it. It's the same principle, applied to metal instead of brick, that guides the practice's entire material research: the material isn't chosen for its appearance on opening day, but for its entire trajectory over time.
A lexicon that goes beyond Herzog & de Meuron
The de Young Museum paved the way, over the following twenty years, for a broader vocabulary of metal envelope as an ornamental, changeable surface in contemporary architecture — perforated or punched metal panels with patterns derived from environmental, cultural or geometric data specific to the site, rather than from a generic decorative repertoire applicable to any building. The underlying logic, common to many later projects by other practices working with metal cladding (aluminium discs, expanded metal mesh, perforated panels), remains the one Herzog & de Meuron demonstrated first: metal cladding is no longer necessarily a neutral, uniform surface, but can be a carrier for specific information — a pattern, an image, a datum — that ties that building, irreplaceably, to its own site and its own history.