Finnish Bent Birch Furniture: Aalto, Korhonen and Identification

Bent birch became central to Finnish modern furniture through collaboration among designers and manufacturers. Alvar and Aino Aalto's work with Otto Korhonen is especially important, but not every curved birch chair is an Aalto design.

Why birch

Birch was widely available in Finland and suitable for veneer, plywood and laminated bending. Its pale colour supported modern interiors, while industrial processing allowed repeatable curved components.

The Paimio Sanatorium conservation plan records Otto Korhonen's knowledge of Finnish birch and manufacturing. It describes the Aaltos' bent-wood furniture as the most original and influential furniture developed for the sanatorium.

Laminated bending

Thin solid-wood strips can be glued and bent in a mould to make curved legs and arms. Plywood uses crossed veneer layers and can be moulded into seats and backs.

Alvar Aalto Foundation records for Armchair 42 describe a combined arm-and-leg “spring” made from thin solid timber pieces glued and bent in a mould. Early examples used beech, changing to birch by 1934.

Paimio chair

The Paimio chair, product number 41, was designed in 1932. Its frame was formed from bent laminated strips, while the seat was birch plywood. Early frames used beech before the move to birch.

Design date and manufacture date must be stated separately because licensed production continued.

Identification

Record:

• exact model number;
• frame profile and laminate count;
• seat shell shape;
• screw pattern;
• labels and stamps;
• manufacturer;
• finish and upholstery;
• repairs and replacement parts.

Curves that look similar can have different radii, layer construction and fixings.

Copies and licensed editions

Artek and authorised manufacturers have produced Aalto designs over long periods. A later licensed chair is authentic production but not an early example.

Generic bent-plywood furniture should not be attributed from material alone. Compare dimensions with foundation and manufacturer records.

Restoration

Delamination reflects both adhesive failure and stored stress. Do not force a curve flat or inject random glue. Preserve labels and original screws.

Avoid sanding plywood edges, which can change profile and expose inner layers.

Sources

• Alvar Aalto Foundation, Armchair 42: https://www.alvaraalto.fi/en/work/armchair-42/
• Alvar Aalto Foundation, Paimio chair: https://www.alvaraalto.fi/tyo/paimio-tuoli/
• Alvar Aalto Foundation, Paimio Sanatorium Conservation Management Plan: https://www.alvaraalto.fi/wp-content/uploads/2023/04/PaimioSanatoriumConservationManagementPlan.pdf
• Museum of Finnish Architecture, Alvar Aalto: https://www.mfa.fi/en/architects/alvar-aalto-2/