The Diamond Chair: Bertoia's Steel Lattice

The Diamond Chair: Bertoia's Steel Lattice

The Diamond chair is recognisable at a glance, and it sits deliberately between furniture and sculpture. Designed in 1952 by Harry Bertoia for Knoll, it belongs to the steel-wire collection the sculptor conceived in one go and which made his name. Its name comes from the diamond shape of its shell, a lattice of welded steel rods that seems barely to press on its base.

A shell made of air

The principle of the Diamond rests on a single idea: a shell bent from a lattice of welded steel rods, wide and open, set on a wire base. Bertoia, a sculptor, thought not of a solid object but of an empty volume bounded by lines. "These chairs are mainly made of air", he said; "space passes right through them." Light passes through the mesh, the shadow draws a pattern on the floor, and the chair, despite its wide seat, looks very light. That transparency is why it fits in easily: it occupies space without blocking it.

Chrome or outdoor finish

The Diamond exists in several surface finishes, which are a first identification marker. The chromed version, in bright polished steel, is the most common for indoor use; its chrome should be thick, even and stable. Knoll also offers an outdoor finish, a Rilsan coating, a technical plastic applied to the steel, available in several colours and designed to resist water and UV. This outdoor version is recognised by its matte, coloured aspect, as opposed to the gloss of chrome. The finish guides the use of the chair and counts in its assessment: an original finish in good condition is worth more than a late re-chroming.

With or without cover

The shell may be bare, leaving the entire lattice visible, or fitted with a fabric or leather cover following its form. The bare version highlights the transparency and the quality of the welds; the covered version adds comfort and a coloured presence while keeping the diamond silhouette. On the vintage market, both versions have their following. An original cover in good condition is an asset; a cover remade outside the workshop should be disclosed, as it alters the authenticity of the piece. The bare shell shows the build quality directly, and it is often the version enthusiasts prefer.

Authenticating a Diamond

A few factual reference points to tell a Knoll Diamond from a copy. The authentic piece is produced by Knoll, which has made the Bertoia collection without interruption since 1952 and applies a marking attesting to the origin. The lattice welds should be clean and even, the mesh homogeneous, with no coarse weld points or gaps. The chrome, on the indoor version, is thick and does not pit; the Rilsan finish, on the outdoor version, is uniform and well adhered. The wire base and its connection to the shell follow a precise geometry. A chair without a Knoll marking, with rough welds, thin chrome that rusts, or a slightly distorted shell, is a copy.

What we check

When a Diamond comes through LAPIERRE MARKET, we look for the Knoll marking and estimate the production period, identify the finish and check its condition under raking light (thickness, evenness, corrosion), then the welds, the lattice, the base and the cover if there is one. Any restoration stays light and reversible. The listing states the model, the finish, the estimated period and the condition. See our Knoll selection.