What is it made of?

95 everyday objects taken apart. Each page lists the components and, for every one, the constraint that made that material the right choice — because a list of materials is a specification, and a specification with reasons is an explanation.

Sport and games

• Tennis ball A pressurised hollow shell of vulcanised rubber, covered in a glued-on wool and nylon felt.
• Golf ball A moulded polybutadiene rubber core inside an ionomer or urethane cover, dimpled all over.
• Soccer ball Polyurethane outer panels over a laminated fabric backing, wrapped around a latex or butyl bladder.
• Basketball A pebbled composite or leather cover over nylon winding and a butyl rubber bladder.
• Cricket ball A cork core tightly wound with wool yarn, cased in four pieces of dyed leather with a stitched seam.
• Bowling ball A dense shaped weight block inside a filler, wrapped in a polyester, urethane or reactive resin coverstock.

Around the house

• Banknote Cotton and linen rag paper, or polymer film — never wood pulp, which is why notes survive the wash.
• Lego brick ABS plastic moulded to a tolerance of about ten micrometres — the tightness of the fit is the whole product.
• Soap Fats reacted with lye to make fatty acid salts — and most modern "beauty bars" are not soap at all.
• Toothpaste Mostly abrasive and humectant, with a detergent for foam — the active ingredient is about 0.15% fluoride.
• Coin Base-metal alloys chosen for wear and cost — most modern "silver" coins are copper-nickel and most "copper" ones are plated steel or zinc.
• Sunscreen UV filters — mineral, chemical or both — suspended in an emulsion whose job is to hold them in an even film.
• Credit card Laminated PVC sheets 0.76 mm thick, carrying a silicon chip in epoxy and a copper antenna coil.
• Candle Wax that is really a fuel, and a braided cotton wick that acts as a pump rather than as the thing burning.
• Lipstick Castor oil carrying pigment, set into a stick with waxes — the oil is the workhorse, not the colour.
• Shampoo Three-quarters water, a primary detergent, a milder secondary one, salt to thicken, and silicone to make hair feel smooth.
• Balloon Party balloons are dipped natural rubber latex; foil balloons are metallised plastic film and are not rubber at all.
• Deodorant Deodorant kills the bacteria that cause the smell; antiperspirant uses aluminium salts to plug the sweat duct. Different products.
• Toothbrush Nylon filaments stapled into a polypropylene handle with a wire — three plastics that cannot be separated for recycling.
• Match An oxidiser and a fuel in the head, with the phosphorus that starts it moved onto the striking strip.
• All 21

Stationery and paper

• Pencil Graphite mixed with clay and fired, glued inside two grooved halves of softwood. No lead, ever.
• Paper Cellulose fibres from wood pulp, plus up to a third mineral filler, sizing and brightener.
• Ballpoint pen A tungsten carbide ball a millimetre across, rolling in a brass socket, fed by thick oil-based ink.
• Glitter Aluminium-coated polyester film, colour-coated and chopped into fragments — by definition a microplastic.
• Crayon Paraffin wax with pigment stirred in, poured hot into a mould and cooled. Almost nothing else.
• Cardboard Two flat kraft paper liners glued either side of a fluted paper medium — the flutes do all the work.
• Eraser Either natural rubber with fine abrasive and oil, or plasticised PVC — two different ways of lifting graphite.
• Blackboard chalk Mostly calcium sulfate — plaster of Paris — rather than the calcium carbonate the name suggests.
• Playing card Two sheets of paper laminated around a black glue core, then coated in plastic — or solid PVC.
• Postage stamp Coated paper with phosphor bands, printed in security inks, on either water-activated gum or a self-adhesive.

Cars and driving

• Car tire Several different rubber compounds reinforced with steel and textile cord — closer to a composite than to rubber.
• Car battery Lead and lead dioxide plates in dilute sulfuric acid, in a polypropylene case — mostly lead, by weight.
• Airbag A coated nylon bag inflated by a small solid-propellant gas generator in about thirty milliseconds.
• Brake pad A friction compound of fibres, fillers and resin, moulded and bonded onto a steel backing plate.
• Windshield (windscreen) Two sheets of ordinary glass laminated to a tough plastic interlayer, which is what stops it falling out.
• Spark plug A ceramic insulator carrying a centre electrode of nickel, platinum or iridium inside a steel shell.
• Seatbelt Woven polyester webbing designed to stretch a controlled amount, plus a locking retractor and a pyrotechnic pretensioner.

Building materials

• Glass Sand melted with soda ash and limestone — three cheap minerals, floated flat on molten tin.
• Concrete Stone and sand glued by cement paste — and it hardens by a chemical reaction with water, not by drying.
• MDF Wood pulled apart into individual fibres, mixed with resin and wax, and pressed hot into a board.
• Road asphalt About 95% crushed stone and sand, glued together by roughly 5% bitumen from the bottom of an oil refinery.
• Brick Clay and shale moulded and fired until the particles partly fuse — a manufactured rock.
• Mirror A sheet of ordinary glass with a microscopically thin silver layer on the back, sealed under paint.
• Plywood Thin wood veneers glued in alternating grain directions — the cross-lamination is the entire idea.

Food and drink

• Marshmallow Sugar syrup whipped full of air and held there by gelatin, which comes from animal collagen.
• Chewing gum A base of synthetic rubber, wax and resin that you never swallow, carrying sweetener and flavour that you do.
• Chocolate Ground cocoa solids and cocoa butter with sugar, plus a trace of lecithin — the fat does the rest.
• Gelatin Collagen from animal skin and bone, broken down with acid or alkali and dried. There is no plant version.
• Cheese Milk protein clotted by an enzyme, drained of whey and salted — four ingredients and a lot of time.
• Bread Flour, water, yeast and salt — plus, in most factory loaves, enzymes, emulsifiers and a mould inhibitor.
• Potato chips (crisps) Thin potato slices fried in vegetable oil, seasoned with a maltodextrin-carried flavour powder, packed in nitrogen.
• Tofu Soy milk curdled with a mineral salt and pressed — cheese-making, with soybeans instead of milk.

Clothing and kit

• Velcro (hook and loop) Two nylon tapes — one of stiff hooks, one of soft loops — copied directly from burdock burrs.
• Leather Animal hide whose collagen has been chemically stabilised so it cannot rot — usually with chromium salts.
• Gore-Tex A stretched PTFE membrane whose pores are far too small for a raindrop and far too big for a water vapour molecule.
• Denim A cotton twill with indigo-dyed warp and undyed weft — the dye sits on the fibre surface, which is why it fades.
• Helmet A hard shell to spread the blow over a crushable polystyrene foam liner that is destroyed by one impact.
• Bulletproof vest Many layers of woven aramid or polyethylene fibre that catch and deform a bullet; rifle threats need a ceramic plate.
• Zip (zipper) Teeth of metal, moulded acetal or nylon coil on a polyester tape, forced together by a wedge inside the slider.
• Synthetic leather A polyurethane or PVC skin on a textile backing — including the plant-based ones, which still need a plastic binder.
• Running shoe A knitted synthetic upper over a foam midsole and rubber outsole — about a dozen materials, all glued together.
• Shoe sole A rubber outsole for grip, a foam midsole for cushioning, and increasingly no clean way to separate them.
• Wetsuit Closed-cell neoprene foam full of nitrogen bubbles, faced with stretch jersey — the gas insulates, not the water.
• Life jacket Closed-cell foam or a CO2-inflated bladder, in a nylon cover — rated in newtons of buoyancy, not in size.
• Button Usually cast polyester resin; the good ones are shell, nut or horn, and you can tell by touch and temperature.

Electronics

• Alkaline battery Zinc powder and manganese dioxide either side of a potassium hydroxide paste, in a steel can.
• Smartphone screen Chemically strengthened aluminosilicate glass over a touch layer and an OLED or LCD panel, with an oil-shedding coating on top.
• Solar panel Doped silicon wafers with silver contacts, sealed between low-iron glass and a plastic backsheet in an aluminium frame.
• LED bulb Blue LED chips under a yellow phosphor, plus a driver circuit and a heat sink — and it is the driver that dies.
• Touchscreen A grid of transparent electrodes measuring the tiny capacitance your finger adds — which is why gloves fail.
• Computer keyboard ABS or PBT keycaps over either a silicone rubber dome on printed film, or individual mechanical switches.
• Headphones A neodymium magnet, a coil of copper wire and a thin plastic diaphragm — a loudspeaker shrunk to fit an ear.
• Loudspeaker A paper or plastic cone hung on a rubber surround, driven by a coil in a magnet gap.
• Computer mouse An ABS shell around a tiny camera taking thousands of pictures a second, plus two clicky microswitches and PTFE feet.

Musical instruments

• Guitar string A high-carbon steel core with a wrap of nickel or bronze — or, on a classical guitar, nylon.
• Piano key A spruce or basswood lever with an acrylic top and a plastic sharp — ivory has been out of use for decades.
• Violin bow A pernambuco or carbon fibre stick strung with horsehair, which grips the string only because of rosin.
• Drum head A polyester film tucked into an aluminium hoop with epoxy — plastic replaced calfskin in the 1950s.

Medical and personal care

• Condom Dipped natural rubber latex, or synthetic polyisoprene or polyurethane for latex allergy — plus silicone lubricant.
• Surgical mask Three layers of polypropylene, of which only the electrostatically charged middle one does the filtering.
• Diaper (nappy) A superabsorbent polymer that holds many times its own weight in fluid, sandwiched between nonwoven plastic layers.
• Contact lens A water-swollen polymer gel — and the whole design problem is getting oxygen through it to the cornea.
• Dental filling Either a mercury-silver amalgam or a light-cured resin packed with glass — and the resin shrinks as it sets.
• Tampon Compressed cotton, rayon or a blend, with a withdrawal cord and either a cardboard or plastic applicator.
• Eyeglass lens Almost never glass — usually CR-39, polycarbonate or a high-index plastic, under several thin coatings.
• Adhesive bandage (plaster) A plastic or fabric backing with pressure-sensitive adhesive, and a pad faced with a film that will not stick to the wound.
• Artificial hip A titanium or cobalt-chrome stem, a ceramic or metal ball, and a crosslinked polyethylene socket liner that is the wear surface.
• Syringe A polypropylene barrel and plunger with a rubber tip seal, and a stainless steel needle on a standard taper.