Lightness and Delicacy

Chris Wilkinson

Lightness is not a technical term and cannot be measured in a finite way. It can be neither quantified nor specified but is a qualitative ingredient of modern architecture which is gaining momentum – and it is a quality we at WilkinsonEyre strive for.

The concept of 'lightness' concerns the physical weight and property of materials, but it relates as much to the visual appearance of structures, components and even spaces. It is a quality that comes from the form, composition and economical use of materials. It also relates closely to light and the way light is treated. Light in itself is a fundamental aspect of architecture, which probably reflects our innate instincts for survival, since we cannot exist without it. It follows therefore that buildings and structures which control light are pleasing to us. Poets muse on the way light plays on water and there is something romantic about the reflections and the dancing movements that come from ripples on the surface. Water can have a powerful impact on architecture by transmitting light and reflecting it onto adjacent surfaces. The magical experience of Venice with its beautiful palazzi reflected in the canals on a sunny day has inspired architects of past and current generations to incorporate water into their designs. Reflecting pools can add lightness and interest. This led us to design the purple pool in front of the entrance to the Dyson Headquarters at Malmesbury and the long rectangular pool at Explore at-Bristol, which reflects the arcade and the planetarium. Both succeed in enhancing the architecture with ever-changing light reflections.

Similar qualities come from the play of light on the surfaces of different materials and form is enhanced by the contrast of light and shade. Curved surfaces deal with light in an appealing way and a curved form will generally appear lighter than a corresponding square or rectangular form of the same volume. Projections and articulations pick up shadows and it is for this reason that traditional mouldings and decorative cornice details serve to enhance the appearance of heavy masonry buildings of the past. Transparent and translucent materials also play with light in an interesting way. Glass is an abundant material in our lives but it still holds almost magical qualities for us. Its crystalline nature catches the light so that it sparkles like jewels. Glass buildings, however, can appear either light and transparent or solid and monumental depending on the lighting conditions at the time of day. Transparency by definition allows space and light through, and seems to offer the kind of freedom that people want. We like to be able to experience the comforts of the inside whilst still enjoying the delights of the outside. We need light from the sun and we like to see it moving round throughout the day, for it helps us to orientate ourselves and to define time. So it follows that buildings which offer this 'light freedom' can be described as possessing lightness. Equally, materials, structures and building forms, which deal with light in a pleasing way, can be said to have 'lightness'.

Mies van der Rohe's Barcelona Pavilion, constructed for the World Fair in 1929, was one of the early examples of the use of storey-height transparent walls to allow the free flow of space and light through from inside to out. This proposed a fundamentally different concept from traditional buildings, where the enclosing walls are solid with punctured openings. Here the walls and roof act as planes which define space without obstructing it, made possible by the steel-frame structure that allows the walls to be lightweight and non-loadbearing.

The combination of steel and glass in modern buildings has significantly lightened their apparent weight and the same qualities can be achieved as effectively in multi-storey towers as with single-storey examples. Even lighter-weight structures can now be achieved with the more recently developed composite fibres and membranes. The really lightweight, high-strength materials such as carbon fibre are still expensive to use in large quantities but membrane fabrics, such as teflon-coated fibreglass, make economic sense for tented structures.

Membrane structures perhaps offer the ultimate lightweight enclosure, the translucency of the fabric, the economy of materials and double curvature forms all adding to a sense of lightness. Recent developments with computer software have made form-finding much easier, so exciting new shapes are now possible and this is an area which we are interested in exploring further.

For inspiration we look at nature, where all the most beautiful plants and flowers possess a quality of delicacy and lightness. There is something inherently appealing about the form of a flower's petals or certain plant and tree forms. It may have something to do with their organic shapes, or it may relate to economy of material or clarity of function. Whatever it is, we feel comfortable with it. Nature is seldom clumsy and I can't think of any examples of heavy monumentalism, with the possible exception of rock formations. It is a pity, therefore, that many of our manmade structures are so heavy and monumental. They seem to draw inspiration from cave-like structures and at best they may be grand or defensive but usually they appear pretentious and self-conscious. I prefer the aboriginal concept of treading lightly on this earth and I believe that this becomes ever more achievable with modern technology.

To explain further the quality of lightness, we have only to look at images of a spider's web, the interior structure of an airship, or a Naum Gabo sculpture. The spider's web is principally light so that it can't easily be seen whilst the interior of the airship has to be lightweight to achieve lighter-than-air lift efficiency. The Naum Gabo sculpture meanwhile, plays with light for visual effect.

Our bridge in the Science Museum's Challenge of Materials Gallery in London is our attempt to explore all these aspects of lightness in a functional structure. With the engineer Bryn Bird, we set out to design a tensegrity structure of steel and glass, which would span the 16m across the atrium with the minimum amount of structural material. The deck is transparent with laminated glass planks laid on edge and these are supported by multiple cables of 1.5mm tensile steel, which are so fine that they are invisible unless they catch the light – like a spider's web.

In a similar way, our Air Pavilion at the Magna Project also uses fine tension cables to support the transparent 'pillow fabric' enclosure. Here the design was worked out with the fabricator Vector and their engineers Atelier One. The cable solution was chosen in preference to a compression ring structure for reasons of economy, but the resultant design also possesses the quality of lightness we wanted within the dark interior space of the redundant Templeborough Steel Reprocessing Plant.

Tension structures invariably look lighter than compression structures and the elements of a structure which support tension forces are usually slimmer and lighter in weight. This is noticeable in bridges where long spans are required, and in particular with suspension bridges, where the slenderness of the deck and the apparent thinness of the supporting cables are accentuated by the scale of the horizontal spans that they connect. For us, this point was emphasized in our competition design for a footbridge across the Seine at the Parc de Bercy in Paris. Working with the engineer Chris Wise, we were able to achieve a span of 200m with cables of only 180mm diameter, onto which the deck was seated. This minimal structure relied on a cable sag of 6m between supports and huge anchor bearings at each end taking loads of 9,000 tonnes from the cables. The incredible visual lightness of the structure is best seen in the working drawings and is compensated for only by the unseen substructure foundations.

Our footbridge at Bedford explores the concept of lightness in a different way – through form. Here the inspiration came from butterfly wings and, working with the engineer John Cutlack of Jan Bobrowski & Partners, we developed the concept for two inclined arched beams from which cables support a lightweight timber deck. The bridge over the River Ouse is sited in a park and the challenge was to create a piece of sculpture in the landscape. Whilst it may not be the most obvious engineering solution, it succeeds in terms of economy of material, visual delicacy and interest. The span is 30m and the total weight of the superstructure is only 18.5 tonnes.

In an entirely different way our Stratford Market Depot for the Jubilee Line Extension achieves lightness through design, even though it requires a substantial structure to enclose the huge space, which measures 100 by 190m. Here the steelwork is fabricated out of circular sections with tapered ends and is clearly articulated from the building skin. The glazed end wall, which returns past the corner to give transparency, and the cantilevered floor structure, with the acuteness of the angle, both contribute to the feeling of lightness.

The detailing of the supporting windframe structure, together with the choice of materials for the south elevation, goes some way to achieving a delicacy and lightness similar to the Naum Gabo sculpture. Here the proprietary translucent fibreglass composite cladding, known as 'Kallwall', was used to provide daylight without solar gain and the effect of the 100m-long uninterrupted wall is rather like the traditional Japanese shogi. The supporting structure is composed of cellform beams, braced with yacht-rigging cables, which provide the visual lightness we required.

Many of these images serve to explain another aspect of our design vocabulary, which is the clear expression of structure and function. For us it isn't enough for the structure to work, it also has to look as though it works properly. At WilkinsonEyre, we always try to separate the major elements, allowing them full expression, and we pay careful attention to the way they are joined together.

Lightness also plays a part in our design of the Dyson Headquarters Building. Here two vast industrial sheds, which house the design, administration, production and storage facilities, are separated by a small glazed pavilion, which forms the entrance to both buildings. The lightweight structure and crystalline transparency of its enclosure give it a lightness, which contrasts with the mass of the adjoining buildings. This is further emphasized by a fabric canopy in front, which floats above the reflecting pool that contains a light sculpture by the artist Diana Edmunds. This sculpture, which is based on the concept of long willowy reeds swaying in the breeze, conveys the very essence of lightness since it is composed of acrylic rods that have been abraded to refract the daylight and glow at night when lit with fibre optics.

Our design for Stratford Station incorporates structurally the concept of 'spatial lightness' through the transparency of the enclosing walls and the specially designed extruded aluminium ceiling surface, which reflects light downwards onto the floor. The mass of the steel-arched structural ribs is revealed and accentuated by the zone of wrap-around curved glazing at the base of the north side and this contrasts with the tension-supported suspended glass wall on the south side. A great deal of effort went into lending visual lightness to this steel truss, which spans 30m across the tracks, and the specially designed stainless-steel bracketry which supports the glazing. In this building all the components have been designed or chosen to create an internal environment which is light and uplifting for the user and which helps to make travelling more of a pleasure than a pain.

Colour is another factor which contributes to the experience of lightness. Of course, light colours help by simply reflecting the most light but the reflection of bright colours can have more exciting effects. I remember seeing a wonderful green reflection on the vaulted ceiling of a gallery at the Miró Foundation in Barcelona which was caused by the sun shining onto the grass lawn outside. The lawn was obscured from view by a solid wall, but the projecting soffit caught the reflections through a clerestory window – the effect was stunning.

We have used bright colour in the staircase enclosures at Explore at-Bristol for identity of circulation and the amount of colour pouring out of the space when you open the doors is a stimulating sight. It is an effect that we have also used in our façade design for the Multiplex Cinema at Merry Hill. Here the auditoria walls, which are painted in bright colours, can be seen through the enclosing building skin which incorporates six different levels of transparency ranging from clear to opaque. The amount of colour seen on the outside is dependent on the level of transparency, which adds visual interest and depth to an otherwise blank façade.

Adriaan Beukers and Ed van Hinte, professors from the Faculty of Aerospace Engineering at the University of Technology in Delft, in their recently published book Lightness, refer to 'the inevitable renaissance of minimum energy structures'. For them lightness is not just concerned with buildings, or aeroplanes, but with 'the structure of all things made and grown'. Their main message is 'the lighter the better', which follows on from Richard Buckminster Fuller's dictum of 'more with less'. But in architecture lightness is not only about weight but also appearance. Perhaps a better description is supplied by the poet Milan Kundera: 'the unbearable lightness of being'.

This essay originally appeared in the practice monograph 'Bridging Art and Science' (Booth –Clibborn Editions, 2001).