Kai Kristiansen Rosewood Dining Chairs, Model 42, Set of Six, 1960s.

A radical, simple piece of furniture, Kai Kristiansen's (b. 1929) Chair #42 perfectly exemplifies Danish modern design’s meld of form, space and functionality.

Produced in 1956 for Danish manufacturer Schou Andersen, the functional and modest properties of Kristiansen’s minimalist dining chair are emphasized when viewed from the front. Admiring Chair #42 from the side tells a different story, however, as the focus shifts from its sharply inclined rear legs and joined armrests to a tilting, floating backrest.

The chair’s profile is dramatic and radical, and examining the frame from this perspective helps clarify why Chair #42 earned the nickname “Z Chair” over the years. Kristiansen’s elegant piece is both simple and technically difficult, its soft lines belying the expert craftsmanship therein while referencing earlier artisan furniture that influenced the Danish modern movement as well as Kristiansen himself.

Trained as a cabinetmaker, Kristiansen studied at the Royal Danish Academy of Fine Arts in Copenhagen under Kaare Klint, who is widely recognized as one of the founders of modern Danish design. The young Kristiansen established his practice soon after, focusing mostly on seating and storage for prominent Danish manufacturers such as Andersen, Fritz Hansen and Magnus Olesen. While he’s largely known for the quality of his designs, Kristiansen was equally comfortable designing chairs, desks, sideboards and wall units.

Kristiansen designed the Model 31 chair shortly after Chair #42 — a similar model, with inlaid arms — as well as the popular Paper Knife series of sofas and chairs. As a designer, he favored teak and rosewood, and garnered major renown for his dark-wood FM modular wall unit in 1957 for Feldballes Møbelfabrik. The customizable shelving system was popular throughout Europe and in the United States, and remains one of the best-known examples of modular shelving, predating Dieter Rams’s 606 Universal Shelving System for Vitsoe by several years. Many of Kristiansen’s designs fell out of production due to their manufacturing challenges, although some collections have recently been reissued by Japan’s Miyazaki Chair Factory.

The stripped-down, spare Chair #42 is one of the earliest modern ergonomic chairs, specifically designed to support the sitter. Suitable for a dining room or as a reading chair, it is Kristiansen’s best-known chair. The piece has effectively remained in production since the 1950s and is currently available from Miyazaki.

With a passion for math and engineering, Kai Kristiansen has created high-quality wood furniture for decades. Beginning in the 1950s, his chairs, modular shelving and other furnishings were made in the style that would become internationally renowned as Danish modern and boasted clean lines, perfected functionality and exacting craftsmanship.

Born in Denmark, Kristiansen trained in cabinetmaking before studying with Kaare Klint, often cited as the “father of modern Danish design,” at the Royal Danish Academy of Fine Arts in Copenhagen. At just 26 years old, Kristiansen opened his own studio.

Kristiansen had his mid-century breakthrough in 1956 with the Chair #42, which he made with Schou Andersen. Unlike most other chairs at the time, Chair #42’s armrests, with their wealth of radical angles, were connected to the back rather than the front legs. This unconventional flourish makes the backrest appear as though it is floating in midair above the seat.

Kristiansen’s next innovation was a modular wall system in 1957 — three years ahead of Dieter Rams’s more famous 606 Universal Shelving System. Called the Reolsystem Wall Unit, produced by SB Feldballes Møbelfabrik, it’s also known as the FM Wall Unit as FM/Fornem Møbelkunst began producing it in the 1960s.

Kristiansen would go on to work with other leading Danish furniture manufacturers such as Magnus Olesen, Fritz Hansen and Vildbjerg Møbelfabrik, designing everything from chairs and desks to sideboards and cabinets, frequently in rosewood and teak. (The latter was a sought-after wood by Scandinavian modern designers.)

While many of Kristiansen’s timeless designs remain in production, such as his Paper Knife sofa, which was reintroduced by Miyazaki Chair Factory in 2008, and his 1950s Entré collection, which was relaunched with Great Dane Furniture in 2016, others are prized as vintage mid-century pieces.

Today, Kristiansen is still at work on new furniture with an expert eye to thoughtfully functional designs that are made to last.

Find a collection of vintage Kai Kristiansen furniture on 1stDibs.