Urushi Shell
Architecture Toyo Ito / Toyo Ito&Associates, Architects Structure Kanada Mitsuhiro / Tokyo University of the Arts Urushi Toki Genji / Miyagi University + Sato Kazuya / Shizen Kobo Landscape Design Lee Sanghoon + Shin Dayoung / VNH + ANPARK Coordination Rishiyagi Urushi Shell Location 38-7 Dongmyung-dong, Dong-gu, Gwangju Photograph Captions Pai Hyungmin
Lacquer, known as urushi in Japan, is a highly durable natural paint and adhesive derived from tree sap. With a long history in East Asia, it has been utilized in crafting bowls, plates, weaponry and tools for agriculture and fishing. Urushi does not generate carbon dioxide during its production and its use can contribute to environmental upcycling though proper forestry. Urushi Shell is a pioneering project, the first of its kind in the world, that utilizes urushi as a structural architectural material.
In pre-modern times, repair and re-use extended the usefulness of things over long periods of time. The Urushi Shell may experience deterioration within a few years but with dedicated care and attention, it has the potential to endure for several decades. To ensure its legacy for future generations, it calls for a strong sense of communal attachment.
In Japan, statues made with dry lacquer are called kanshitsu statues. Urushi Shell is an architectural interpretation of this technique of stacking layers of hemp or cotton on clay, applying lacquer several times, and then removing the clay to create a hollow structure. Resembling a carbon fiber structure, the Urushi Shell is a fusion of ancient craftsmanship and modern prefabrication.
Toyo Ito&Associates, Architects
Taking urushi sap from Urushi Tree and cotton mesh treated with urushi. The Toyo Ito team is collaborating with Professor Genji Toki of Miyagi University, who has developed a modern system of kanshitsu ( geonchil in Korean), and Professor Kanada Matsuhiro, who is working on a structural urushi system. Traditional kanshitsu includes painstaking sanding and intricate brushwork. Toki has developed a technique that may use rollers and room temperature drying. With the multiple layering of lacquer, rice glue, earth, and thin cotton sheets, urushi panels take on structural properties.
Urushi sheets can be produced in large sizes and then laser cut to the required shape. Urushi Shell is being made with this type of work which locates itself somewhere between craft and industry. Urushi Shell is composed of panels made of six-layer urushi sheets plus three-layers of UV resistant urushi and fiber sheets constructed in a honeycomb pattern.
Urushi crafts people working in Toki’s Miyagi University studio. During the past 10 years, Toki Genji and Kanada Mitsuhiro, through their academic and company work, have designed and produced products including traditional items such as bowls and plates. As they have expanded into furniture, urushi has been used as a structure similar to the way carbon fiber is used in modern vehicles. The Miyagi University urushi studio has a range of facilities from a traditional drying closet to state-of-the-art digital fabrication machines. To expand lacquer in modern life, Toki and Kanada have integrated thousands of years old craft techniques, digital fabrication and robotics.
Geocrete shell mock-up test in Tokyo University of Art, geocrete sample tests, and various design based on geocrete, conducted during spring and summer of 2023. As a project to provide an environmentally friendly resting shelter in a public outdoor parking lot, Ito Toyo initially worked on a geocrete shell up to the stage of a mock-up. With doubts about the overall quality of the shell intended to be built without formwork, a decisive change in material direction toward urushi was made.
Immediately after the shift from geocrete to urushi, the Ito team started to devise a structural and fabrication system for an urushi shell. The shell consisted of 3 dimensional honeycomb panels pulled together by wires as a series of arches. During the late summer and fall of 2023, while Toki’s Miyagi University produced the sample panels, Kanada’s Tokyo University of Arts team built the shell mock up.
The urushi panels of the mock-up ceiling were 3 dimensional curves. Flat double layer urushi sheets were bent without any machinery and glued onto the honeycomb frame with Cemedine. Based on this successful mock-up, the design of the actual shell was developed. Structural analysis of the shell required that the urushi sheets, which take on most of the structural burden, required 6 sheet layers. The thicker sheets did not bend as with the mock-up, which led to several experiments in making a 3-dimensional PVC mold. The final design finds a middle ground with the panels bending in one direction.
Paper honeycomb frame of the mock-up panel. A key issue in material design was to find a material for the honeycomb frame that would be fully integrated with the outer urushi sheets of the actual shell. Paper and wood were considered but a natural fiber product of a Japanese company was identified, one with appropriate rigidity and cutting properties.
Structural load testing on samples made in Korea conducted at Kanada’s laboratory at Tokyo University of the Arts. Korean samples demonstrated 70% of the strength of the sample panels made in Japan. The Korean lacquer team had made panels according to the manual provided by the Ito team. The Korean team went through 3 sample cycles but their structural performance, laser cutting accuracy, and finish did not fully match the Japanese samples leading to the decision to produce the urushi sheets in Japan and the honeycombs in Korea.
The actual Urushi Shell, consistent with the principles of the mock-up, took the form of an open egg shell. An early version of the final design had two arch openings. However, production issues with irregular panels, wire connections, edge detail of the arches proved too complicated, and hence a single arch design with a clearer building logic was finalized. Professor Kanada has called the structural logic of the Urushi shell as one similar to an igloo.