Here, a juxtaposition of chairs on display at Designmuseum Danmark shows how a designer can return to a shape or, in this example, rework a design in different materials that have different qualities and dictate very different manufacturing techniques.
Shown together are a bentwood chair from the early 20th century - an arm chair from the Austrian company Thonet from 1904 - alongside two chairs from the third quarter of the century by the Danish designer Poul Kjærholm.
Kjærholm's version of a bentwood chair PK15 is in beech and dates from 1978/1979, just before the designers death, and the steel and leather chair PK 12 was actually designed by him in 1964.
Both the classic Thonet chair and the version by Kjærholm use screws and bolts to fix the separate parts together and both use a bentwood hoop below the circular seat to give the legs strength and the chair some rigidity … in bentwood it’s not possible to use stretchers between the legs that are fixed in place with mortice and tenon joints as in a traditional chair frame.
The Austrian chair revels in the sharp curves that could be made with steamed and bent beech but Kjærholm refines and simplifies the curves to produce a design that is much more restrained although both chairs have long, high curved side arms - on the earlier Austrian chair swept back under and fixed to the side of the seat but on the Danish chair integral with the front legs.
Both chairs have woven seats.
Again to strengthen the frame, the earlier chair takes the sweep of the back and the hoop of the back legs together. Kjærholm separates the two curves but has a small and simple spacer at the centre.
Initially, the steel chair appears to have the same shapes and curves as the later chair in beech but of course the metal dictates very different details in the construction. The strength of the metal tubing means that the hoop below the seat can be omitted completely as can the spacer at the back and the two curved sections of the inner loop of back legs and outer arch, with the front legs and the arms in a single piece, are attached to the rim of the seat by short stubs of metal with the parts welded together. The seat is not circular but rather like a distorted ellipse and the seat is a leather pad dropped into the seat rim rather than being woven.
A version of the PK 12 that was made by E Kold Christensen has the upper sweep of the back bound in leather, the strips plaited around the steel, and matching the leather of the seat.