Milan 2015: French designers Ronan and Erwan Bouroullec have created two chairs and two tables for Swiss furniture brand Vitra, which will debut at Milan design week next month (+ movie).

The Belleville collection includes two variations of a chair with a frame made from black polyamide plastic. This supports a shell that comes in four different versions – polypropylene, ultra-thin 4.5 millimetre plywood, or upholstered in fabric or leather.

According to the duo, the idea behind the Belleville chair was to create a flexible product that can be used indoors or outdoors.

"From one side, the polyamide version allows heavy-duty outdoor locations," the designers said. "While on the other hand, the upholstery and plywood shell versions belong to a softer landscape."

The single-piece frame is made with an automated injection-moulding process that uses gas to quickly place pressure on the molten material and form it into shape.

"Injection moulding with gas is a technique that asks for massive engineering before production because there are no room for possible errors with this kind of tool," said the Bouroullecs. "Production is about 3-4 minutes only, and then everything is finished."

The frame for the armchair appears to travel in a continuous line, curving forwards from the angled back legs up into the arms, and then looping around to form a narrow backrest that widens into the seat. The second version is more linear, with the back rising up from the legs and across the top.

"The 'one line' frame structure links the feet to the shells and continues into the armrests and into the backrest," said the designers.

"Like a typographer does with the design of a letter, step-by-step we valued the proportions of this line in order to make it well balanced, but also to answer the demands of the production technology."

The Bouroullec brothers recently debuted bent-steel tables and shelving for Vitra-owned Finnish brand Artek, while at Milan last year the two announced their first fabric collection for Kvadrat.

Also in the Belleville range are two tables – one round and one rectangular – with black powder-coated cast aluminium legs, with tops in laminate wood or stone.

Ronan and Erwan Bouroullec will display the collection at the Vitra stand, Hall 20 at Salone del Mobile.

Photography by Studio Bouroullec.