028 – Soft Poly Chair

Soft Poly Chair
Expanded polystyrene, polyurethane
1200 x 1000 x 610

A process of destruction is used to construct a bombproof chair. A claw hammer and a reasonable amount of energy is all that is required. By making furniture by hand the unique is achieved and individual beauty inevitable. The chair takes less than 30 minutes to carve and the polyurethane rubber finish takes only 10 minutes to apply. The chair is ready to sit on just 40 minutes from the start of production.

Expanded polystyrene is typically used as a packaging material. Its impact absorbing and insulating properties, and complete weightlessness, make expanded polystyrene perfect for packaging fragile goods. Polystyrene is made up of thousands of tiny balls of plastic foam, known as beads, ranging from 2mm in diameter to about 8mm. The size partly refers to the amount of expansion that occurs during production, but also the original size of the styrene granules prior to expansion. The pre-expanded polystyrene granules are less than 0.3mmØ. The granules are first steamed causing them to expand to almost 100 times their
volume and are then fed into vast hoppers. The expanded beads are as much as 98% air. To turn the loose beads into moulded blocks a further process is required: the expanded beads are injected under pressure into an aluminium cavity mould of the desired size and shape, and steam is pumped through thousands of inlets covering the surface of the mould, usually in circular patterns. The combination of steam and pressure causes the beads to expand even more and naturally fuse together. The mould is opened and the one-piece expanded polystyrene block is released.

Soft Poly Chair began as an exercise in modelling armchairs and sofas using expanded polystyrene as a material with which I could realise my ideas quickly, easily, and most usefully, full-size. The surface of the material is quite fragile, breaking into little white beads easily under friction, but structurally polystyrene is in fact surprisingly strong. This is due to the closed cell structure of the foam beads. I contacted various polystyrene companies and visited a manufacturer in Gateshead called Sundolitt, where I learnt about the expanded polystyrene production process. I discovered the standard block sizes were perfect for sculpting sofas and armchairs from: 1220mm x 1220mm x 610mm is an ideal size for producing a single seat armchair, and 1220mm x 2440mm x 610 is perfect for a three seat sofa.

There are many densities of expanded polystyrene available. I received samples of each of the common densities and established that the lowest density, EPS 20, was the easiest and quickest to carve, the most comfortable to sit on, and still remarkably strong. A claw hammer proved to be the most efficient tool for sculpting the polystyrene. It also proved to be the most fun. In fact, it was my experiments with different tools that informed the overall shape and form of my armchairs and sofas. The claw hammer generates a rough, inconsistent texture, similar to that of granite. The process of hitting into a square block of polystyrene and breaking huge chunks of material away from the clean faces was quick, spontaneous and satisfying.

Though my use of polystyrene began simply as a method of modelling my designs, I soon realised polystyrene had huge potential for furniture itself. Expanded polystyrene allows the production of a full size, fully functioning and comfortable armchair, by hand, in just 30 minutes.

The only problem with polystyrene is its fragile surface, easily broken with a slight knock. The challenge was to seek a material with which to cover or ‘upholster’ the polystyrene to protect the surface, without losing the inherent texture and softness of the foam beads. I also wanted to maintain the speed of the chair’s production. A variety of stretchable fabrics are readily available, but I wanted my chairs to differ from existing upholstered chairs. The idea of a material that could be painted or sprayed over the surface appealed – one that completely encapsulates, but assumes the shape of the polystyrene form. Rubbers, both natural and synthetic, exist in hundreds, so to choose a suitable one with which to ‘upholster’ my chair was simply a process of research and experimentation. Natural rubber would have been my first choice, but it perishes
in UV light and moisture extremely quickly. There are stabilisers that reduce the effects of weathering, but these only slow down the process. Another problem I found with latex is the length of time it takes to dry and its low viscosity.
Coagulants are available to speed up the drying time, and thixotropic additives to thicken the consistency of latex, but its perishability rendered it unsuitable.

I discovered a company who spray hard rubber bed-liners onto pick-up trucks. Known as XS- 100 the spray is extremely tough, flexible and highly UV stable. In addition, the two-part thermo-reactive spray dries in just three seconds. It sounded perfect so I visited the Devon-based company, called Line-X, and took with me an unfinished polystyrene chair to be sprayed. The standard colour for applying to trucks is black, although almost any colour is available. Black was
chosen as it is both the cheapest and easiest colour for spraying onto a white polystyrene surface. I placed the chair in the huge walk in spray booth and Neil, the master sprayer, began to coat the chair. The chair took less than 10 minutes to coat, and as soon as Neil gave me the thumbs up, I entered the spray booth and my rubber upholstered chair could be sat on. Although the Line-X spray is advertised as a rubber, I hadn’t realised the difference between the various shore hardnesses. Shore A is the softest, most flexible and rubbery of the rubbers, and the coating covering my polystyrene chair was shore D. It feels like hard plastic, and unfortunately all the softness and ‘give’ inherent to polystyrene was lost. The chair did become bombproof, however, quite literally. The rubber is used to coat military vehicles to reduce fragmentation and ricochets, and to line the walls of buildings such as the Pentagon and banks for bomb blast mitigation. Since the first armchair I have reserved the use of XS-100 as a sort of spray-on exoskeleton for chairs and other pieces of furniture which
require additional strength and rigidity. And for armchairs and sofas I use the softer, lower shore hardness rubber known as XS-75 which has a slower but still impressive drying time of 20 seconds.