And even from assuming that a chair is simply a machine for sitting on

And even from assuming that a chair is simply a machine for sitting on.Langlands & Bell, to 27 May, Serpentine Gallery, Kensington Gardens, London W2 (0171-402 0343)Ben Langlands and Nikki Bell will give a lecture on their work on 21 May, RIBA Architecture Centre (address below); credit card bookings, 0171- 631 0460 between 1pm and 5pm, Monday to Friday or buy tickets from RIBA bookshop.Products of Desire, to 25 May, RIBA Architecture Centre, 66 Portland Place, London W1 (0171-580 5533)100 Masterpieces, to 6 October, Design Museum, Shad Thames, London SE1 (0171-403 6933).. In between Langlands & Bell and the hospital furniture of ABK is a pantechnicon of designs and design ideas that, ranging from the practical to the polemical, keep us free from thinking in constricting straight lines and from assuming that the plan of our banal modern offices is neutral. No one goes to John Lewis to buy an ironic statement when what they want is an iron. Or to buy an iron with a smoothing surface studded with spikes. The latter belongs to the art gallery.Back at the Serpentine, Langlands & Bell re-introduce us to the idea that architecture and furniture are perfectly valid media through which the artist can explore lines of enquiry and personal obsessions. Charles Holden’s design for a London bus was far less imaginative and forward looking than London Transport’s own engineers; the architect was treating the double-decker as a mobile building rather than a vehicle.Product designers, in contrast to architects and artists, rarely indulge in rhetoric and philosophising in the things they shape.

Architects and artists do not always make good product designers. Buildings tend to be much less sophisticated objects than, say, cars. When Le Corbusier attempted to design a city car (there is a full-scale wooden model of this in the Design Museum) or Mies van der Rohe a limousine, the results were all but risible. Le Corbusier’s city car, a fascinating shape, would have been a nightmare to drive, while Mies’s limo was, judged by the work of the great car designers and engineers, as old-fashioned and awkward as a carriage clock. Here, you can come to grips with door handles by Norman Foster, Richard Rogers and Nicholas Grimshaw, and encounter a Neo-Constructivist coffee set by Zaha Hadid, wilful furniture by Piers Gough and Procter-Rihl, cool light fittings by Rick Mather, a rowing boat by Nic Bailey and, on a more clinical note, hospital furniture by ABK (Ahrends, Burton and Koralek).While some of the pieces on display are decidely functional and with widespread, if not universal, application, others are prototypes or test- beds for new ideas.

It is unlikely that anyone would sit for very long on a hand-painted Mendini armchair.The same criticism – can’t sit on it, it’s impractical – has been levelled at some of the designs on show at the RIBA Architecture Centre. The Post-Modern excesses of Italian architects, including Alessandro Mendini (Poltrona di Proust, 1978, a deliberate trivialisation of Baroque architecture and Impressionist painting) and Ettorre Sottsass (Carlton, 1981, a perverse shelving system veneered in wilfully banal laminates) were precursors of the most extreme (what the Italians liked to call “ironic”) statements of Post-Modernist architecture. For many architects over the past century it has been a method of exploring new avenues in design long before it was possible to erect a building in the same or similar idiom. Bauhaus architects, including Marcel Breuer and Ludwig Mies van der Rohe, fashioned famous chairs (still in production) in the 1920s before they were able to translate the ideas embodied in these designs into radical buildings.Equally, the blow-up plastic chairs of the mid-Sixties, although fun to sit on, were intended to be more an exploration and celebration of the possibilities of new materials and manufacturing processes than the Sheratons of the day. That caustic Victorian Goth, Augustus Welby Northmore Pugin, commented in the 1830s that is was difficult for the visitor to a Regency Gothick home not to be impaled by the fashionable and spikey furniture.But furniture is propaganda and criticism as well as a functional and decorative tool.

It isn’t, but it was never really anything more or less than a commentary in furniture of the investigations of the painter Piet Mondrian. In other words, it was a Langlands & Bell of its day.Yet, the intolerance for this sort of design – design as a critical commentary or artistic statement – continues to be frowned upon. One thinks of Frank Gehry’s Wiggle side chair (1972), a Pop sculpture conjured from corrugated cardboard. One thinks, too, Gerrit Rietveld’s Zig-Zag chair (1932) or famous Roodblauwe stoel (1918), which is still sold today in flat-packs for easy assembly. Everyone who owns one tries hard to convince visitors that it is comfortable to sit on. Drawn from the incomparable collection of modern chairs assembled by Ralf Fehlbaum, chairman of the furniture manufacturer Vitra, the other 99 “Masterpieces” include designs that were as much commentaries on contemporary art and design theory as they were practical pieces to sit on. Two exhibitions running concurrently with the Langlands & Bell show – “100 Masterpieces” at the Design Museum, London and “Products of Desire” at the RIBA Architecture Centre, London – take up the theme of designing abstract furniture, or furniture designed as art or propaganda rather than for merely sitting on or eating at.The Design Museum show begins practically enough, with garden chairs designed by the great Prussian classicist Karl Friedrich Schinkel in the early 1820s.

Their decor choice was collaborative, “but the final decision was Sergio’s,” says Keaveney.The project is immense, but it is subtlety, not scale, that makes it work. The delicacy of touch hits home in the way existing features, such as intricate carved-wood door-frames by Carlo Cambi of Siena, previously overshadowed, have been enhanced by new backgrounds to become handsome adornments against muted mushroom and pistachio shades.A special multi-media viewing room with a rapid retrieval system will allow scholars and others easy access for the first time to items in storage from a total collection of 13,000 works.The job began, however, with the basic fabric of the building: heating, lighting, ventilation have all been upgraded, with London Tube-sized lifts carrying 60, and wheelchair-friendly ramps aiding movement.Another Irpounds 14m (pounds 14.6m) will complete the final stage, to be finished in the year 2000, when the gallery will have another 50,000 square feet on recently acquired adjacent land – 40 per cent more than at present.A key feature there will be a gallery-within-a-gallery, the Jack B Yeats Museum, featuring works by the artist brother of the poet WB Yeats, including a major family bequest of sketchbooks, studio contents, a library and family memorabilia. Aside from the fact that the chairs are very beautiful, they turn upside down the perfectly sensible commonplace notion that chairs sit inside buildings: in Langlands & Bell’s world, buildings sit inside the chairs.Can you sit on them? Art galleries will be keen to discourage the idea, but, yes, you can, although that is not the point of the pieces and anyway, since the time of the ancient Egyptians, chairs have not always been designed for sitting on.That is certainly the case of many of the chairs architects have designed over the past 70 or 80 years. They have developed this theme of architecture-into-furniture over a number of years. Both Hirst and Langlands & Bell chose to encase their subject matter and celebrate the cases as much as the shark or scalped buildings caught inside them.Langlands & Bell have explored this theme further in a sequence of seven white and elemental chairs they call “Maisons de Force” (1991), on show at the Serpentine. Each seat has the model of a famous prison built into the seat under glass.