Bertoia Wire Chair for Knoll: original, reissue, counterfeit
Harry Bertoia (1915-1978), the Italian-American sculptor trained at Cranbrook Academy, designed for Knoll in 1952 a family of welded steel wire seats that became one of the mainstays of the company's catalogue: the Diamond Chair, the Side Chair, and the matching stool and armless chair. "The chairs are mainly made of air, like sculpture," Bertoia said, and the phrase sums up why authentication is difficult. A Bertoia is above all a drawing in space, easy to copy in appearance and hard to copy accurately. Here are the points to check.
The Bertoia models for Knoll
Diamond Chair (1952)
An enveloping armchair in welded steel wire on a four-branch base, in a standard and a wide version (Large Diamond). The seat cushion is sold separately. Finishes: chrome, bonderised (the historic white epoxy coating), then black lacquer, and gold plating in a limited edition.
Wire Side Chair (1952)
A stacking chair with a steel wire shell on a steel rod base. It comes in two versions: Side (without arms) and Arm (with arms).
Stool and armless chair
Variants within the same range, produced alongside it.
Dating and authenticating
The Knoll markings
Older Bertoia pieces carry a Knoll marking that changed over time:
- 1952 to the 1960s: a paper label or "Knoll Associates" stamp, sometimes removed or damaged.
- 1970s-1980s: a metal or adhesive "Knoll International" label, with a New York address.
- After 2000: laser marking or a coded label with product references.
A missing marking is common on older pieces, but it then calls for an even closer technical examination.
The welds
This is the most revealing technical point. On an authentic Knoll Bertoia:
- The weld points between the wires are regular, well aligned and polished.
- The number of points per intersection is the same throughout a given model.
- The wires have exactly the same diameter from end to end.
Counterfeits usually fall short on one or more of these points: messy welds, extra or missing points, slight variations in wire diameter from one batch to the next.
The finishes
- Knoll chrome: bright, hard and even, with no bluish haze and no spiral micro-scratches, which are the sign of cheap polishing.
- White bonderised lacquer (Knoll's historic finish): thicker and more matt than today's industrial lacquers. On an older piece it often shows small surface chips, which reflect its age.
- Fixings: on an authentic Knoll, the fixing points between shell and base are clean.
The base
On a period Diamond, the base is made of four branches of solid chromed steel wire, welded together with a central fixing plate. Copies often use a hollow tubular base, which you feel immediately when you lift the chair.
Counterfeits: what they get wrong
Bertoia counterfeits are very common, especially of the Diamond. They usually fall down on:
- The chrome (haze, a yellower tone, spiral scratches).
- The welds (irregular, messy, or hidden under epoxy powder coating).
- The weight (lighter, hollow base).
- The comfort (the curve of the shell is slightly wrong, and the seat "breaks" towards the back).
A new standard Knoll Diamond Chair costs around 2,000 to 2,500 euros depending on the finish. A new Diamond under 1,000 euros is bound to be a copy.
Reissue or original: the question of value
Knoll has produced Bertoia's seats without interruption since 1952. Every piece from official Knoll production is authentic, whatever its decade. For a collector, it is the period that makes the difference:
- 1952 to the 1960s: historic pieces, sought after by collectors, especially in their well-preserved original white bonderised finish.
- 1970s-1980s: volume production, bought for use, at stable prices.
- After 2000: recent pieces, which resell as second-hand new pieces.
A 1950s Diamond in original condition can sell for clearly more than a new Diamond. A 2015 Knoll Diamond is worth roughly its purchase price, less a discount for use.
In practice
Behind its apparent simplicity, the Bertoia is hard to copy accurately, and the gap between an original and a copy lies in fine details. For a buyer, the safest approach is to cross-check marking, welds and weight; when the marking is missing, the other two must be faultless.
FAQ
Can a Diamond without a label be authentic? Yes, it is common on older pieces. Authentication then rests on the quality of the welds and the chrome.
Does Knoll certify its older pieces? Knoll keeps archives for recent production. For pieces from 1952 to 1980, you need to go to specialists in twentieth-century American design.
Are gold finishes authentic? Knoll produced limited gold-plated editions. Outside those documented editions, a gold finish should raise suspicion.
Does the Diamond cushion matter for the price? An original cushion in its period colour adds value to the piece. A remade cushion improves comfort without changing the price much.
Which periods are the most sought after? Production from 1952 to 1965 in the original white bonderised finish, with a Knoll Associates label.
Further reading
By
LAPIERRE MARKET
