Choosing materials: function, aesthetics and the environment

For a few years, bamboo coffee cups were everywhere, sold as the green choice. They were earthy to look at, light and cheap. Then food safety checks found that some could leak chemicals into hot drinks, and some countries took them off the shelves. Most of them could not be recycled at all. A cup chosen to help the environment turned out to be worse for it. How does a designer get a material choice that wrong? That cup passed on looks, and failed two other tests a designer always runs.

Every material choice is judged on factors: the reasons a material or a component is right, or wrong, for one product. A component is a ready-made part, like a hinge or a screw. There are eight factors on the list you are examined on. This video teaches the first three: function, aesthetics and the environment. Function comes first, and it has two halves. The first is application of use: what the material must do in this product, like carry a load, keep water out or be safe with food. The second half is ease of working: whether the material can be cut, shaped, joined and finished with the tools and processes you have. Take a reusable picnic plate. It gets packed in a bag, carried to the park and dropped on a patio more than once. Ceramic or polypropylene for that picnic plate: which suits, and why? Polypropylene, or P P for short. It is tough, so it takes a knock without cracking, while ceramic is hard but brittle and shatters on the first drop. Application of use goes further than knocks. The plate holds hot, greasy food and goes in a dishwasher, so the material must be food safe, resist moisture and cope with heat without warping. Ease of working matters because thousands of plates are needed. Polypropylene granules can be injection moulded, which means melted and forced into a shaped mould, so each plate comes out in one step. Carving each plate from timber would take far longer. Here are two answers about the plate's function. One says the plate should be round and comfortable to hold. The other says polypropylene is tough, so the plate will not crack when it is dropped. Which of those two answers scores, and why does the other one not? The polypropylene answer scores. It is about the material and what it must do, while the first answer only describes the product's shape. One examiner's report puts it this way. Some students focused on products without linking to the specific question demands of material and components. This meant that some responses did not answer the question. This was particularly evident for the first factor of product function. In plain words, those answers described the product and forgot the material. The fix is to write every point as a linked point: the material, what it must do, and so what for this product. Function is also judged part by part. A chair's seat, frame and fixings each do a different job, so each part can need a different material. The same thinking picks materials for a prototype, a trial version built before the real product. A designer wants a first rough model of a desk phone stand, to try it out on a desk. Card or the real acrylic for that first mock-up: which suits, and why? Card. A mock-up only has to show the shape and size, and card cuts with a craft knife in minutes. The real acrylic waits for the working version, because that one has to do the real job.

Aesthetics is how a material or component looks and feels. It covers three things: surface finish, texture and colour. Surface finish is how the outside is treated, such as polished, brushed or painted. Texture is how it feels to the touch. Colour, with any pattern, is what the eye takes in first. Aesthetics also asks whether a material will keep looking good after years of hands, water and knocks. Here are five things you might write about a material. The first is resists scratches, the second matt black finish, the third can be recycled, the fourth smooth to the touch, and the fifth waterproof. Which two of those five are about aesthetics? Matt black finish and smooth to the touch. One is a look the eye takes in, and the other is a feel the hand picks up. Waterproof is function, and can be recycled is the environment. Resists scratches is a property, so it sits with function, until you say what it protects: a finish that stays looking new. One examiner's report names the problem. There were several instances where students showed little or no understanding about the meaning of the word aesthetics. As a result, responses were sometimes inappropriate, for example talking about recycling as well as functional requirements of materials. Those answers drifted into the other two factors. The fix is to anchor every aesthetics sentence in a finish, a texture or a colour. Here is a line that turns up in answers about looks: the oak makes the handles more aesthetically pleasing. What is missing from that line about the oak handles? A named quality, and its effect. It only repeats the idea of looking good, and never says what about the oak looks good, or so what. A named quality needs its effect, joined by so. The oak's visible grain gives a warm, natural look, so it suits a farmhouse kitchen. Components count in aesthetics too. Hinges and screws can be hidden inside a cupboard door, so the front looks clean and unbroken. One examiner's report singled out answers like that. Some impressive responses such as considering component positioning, for example hinges and screws being hidden to improve aesthetic, were rewarded. The way to earn that is to name the component, then say what hiding it does for the look. Now a full answer. A designer is choosing the material for the handles on a set of kitchen cupboards, and has to explain why aesthetics matters, with an example. Write two aesthetic points for those handles, each one joined by so. One strong choice is brushed stainless steel. Its satin finish hides fingerprints, so the handles still look clean in a busy family kitchen. And the look must last: stainless steel will not rust or dull under wet hands, so it still looks new years later. In a farmhouse kitchen, oak's visible grain would suit better, so the kitchen's style decides the material.

The environment factor asks two questions of a material. Can it be recycled once the product is worn out, and does it already contain recycled or reused material? Recycled means broken down and made into new material, and reused means used again in the form it is in. Metals and most thermoforming polymers can be melted and remade again and again. A thermoforming polymer is a plastic that softens every time it is heated. A thermosetting polymer is different: it sets hard for good when it is made, so it cannot be melted down and remade. Now look inside the bamboo cup. Its wall was bamboo powder, held together by a resin called melamine formaldehyde. That resin is a thermosetting polymer. Why does that stop the cup being recycled? It set for good when the cup was made, so it cannot be melted down and turned into anything new. A cup sold as green ends up as rubbish. Many picnic plates use the same resin. It is hard and copes with heat, but like the bamboo cup it cannot be recycled, which is one more reason the polypropylene plate wins. The environment factor also asks where a material comes from. Timber is renewable, because trees can be replanted. Most plastics come from oil, a finite resource, which means it will run out. And most plastics are non-biodegradable: they will not rot away. One examiner's report records where many answers stopped. The majority of candidates concentrated on information about how plastic was non-biodegradable. That point is true, but it is only half the story. The fix is to add the rest: where the material comes from, and whether it can be recycled or reused. Try that on a real choice. A garden-furniture maker is choosing between new hardwood and recycled high density polyethylene, H D P E, made from old milk bottles, for the slats of an outdoor bench. What is one environmental reason for the recycled slats, one against, and your verdict? For: the slats reuse plastic that was already thrown away, so it stays out of landfill and no trees are felled. And H D P E is a thermoforming polymer, so the slats can be recycled again later. Against: H D P E comes from oil, a finite resource, and if the bench ends up in general waste, it will not rot away. Well-managed hardwood is renewable, and wood rots back into the soil. The verdict: for a bench that sits out through years of rain, recycled H D P E is the better environmental choice. It reuses waste, needs no treatment and can be recycled again, as long as someone collects it at the end. One side, the other side, then a verdict tied to this product: that is what a good weighing-up looks like when choosing a material.

Let's test all three factors, with one question on each of them. Aesthetics covers three things: what are they? Aesthetics covers surface finish, texture and colour: how a material looks, and how it feels. Now a different one: why is a melamine salad bowl a poor environmental choice? Melamine formaldehyde is a thermosetting polymer, so the bowl cannot be melted and remade. When the bowl is worn out, it cannot be recycled either. One more: what is a function point for a polypropylene bike mudguard, with a so? Polypropylene is tough and resists moisture, so the mudguard survives stones and months of wet roads without cracking. And the bamboo cup looked the part. It failed on function, because its resin could leak chemicals into hot drinks, and on the environment, because it could never be recycled.

If you could now write a linked point on function, looks and the environment, give this video a thumbs-up. That marks it as in the bag, so you can skip it next time you revise. If it has not landed yet, save the video or the whole playlist instead. The next two videos keep using these three factors, so they will come back round anyway.

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