Processes

Transformations that turn one material into another.

• Acheson process

  Baking sand and coke together at nearly 2,500 °C — the route to silicon carbide, and to the synthetic graphite that electrodes and battery anodes are made from.

• Air separation

  Liquefying air and distilling it into its components — the source of industrial oxygen, nitrogen and every noble gas but helium.

• Alloying and melting

  Dissolving one metal into another while molten — the oldest deliberate materials engineering there is, and still how every alloy is made.

• Anodising

  Grow the oxide deliberately instead of letting it happen — a surface that is part of the metal rather than a coating on it.

• Basic oxygen steelmaking

  Blowing pure oxygen through molten pig iron to burn out its carbon — the step that turns brittle iron into steel, in about twenty minutes.

• Bayer process

  Dissolving alumina out of bauxite with hot caustic soda — the refining step between the ore and the smelter, and the source of red mud.

• Brine evaporation

  Concentrating salt water in the sun until what is dissolved in it crystallises — the source of most of the world's lithium, bromine and iodine, and of solar salt.

• Calcination

  Heating a material below its melting point to drive off a volatile component — classically CO₂ from limestone.

• Casting

  Pour it in liquid and let it freeze into the shape of the cavity — the oldest way to make a metal object, and still the only way to make some.

• Chlor-alkali electrolysis

  Electrolysing brine into chlorine, sodium hydroxide and hydrogen — three products in fixed proportion whether or not demand agrees.

• Claus process

  Recovering elemental sulfur from the hydrogen sulfide stripped out of natural gas and crude oil — the reason sulfur is a by-product of pollution control rather than a mined commodity.

• Contact process

  Oxidising sulfur dioxide over a vanadium catalyst to make sulfuric acid — the largest-tonnage chemical process in the world.

• Cyanidation

  Dissolving gold out of crushed rock with a dilute cyanide solution — the method that made low-grade ore worth mining, and the reason gold mining is an environmental argument.

• Czochralski process

  Pulling a single crystal slowly out of a melt — how every silicon wafer in the world begins, and how synthetic sapphire is grown.

• Electrorefining

  Dissolving an impure metal anode and replating it pure — and collecting, in the sludge beneath, most of the world's tellurium, selenium and precious metals.

• Extrusion

  Push a softened material through a shaped hole and it comes out that shape, continuously — pipe, film, fibre, window frame, and the same idea in aluminium.

• Firing

  Heating shaped clay until its minerals break down irreversibly — the transformation that separates pottery from mud, and why it survives in the ground.

• Float glass process

  Forming flat glass by floating molten glass on molten tin, giving both surfaces a perfect finish without polishing.

• Forging

  Deform it solid, and the grain flows with the shape instead of being cut through — which is why the critical parts of a machine are forged and not cut.

• Froth flotation

  Separating a mineral from crushed rock by making it stick to air bubbles — the step that turns a rock containing half a per cent of copper into a concentrate worth smelting.

• Glass melting

  Melting sand with a flux and a stabiliser, and cooling it fast enough that it never gets the chance to crystallise.

• Hall–Héroult process

  The electrolytic reduction of alumina that made aluminium a commodity rather than a precious metal.

• Heat treatment

  Change the properties without changing the composition — the reason two pieces of identical steel can differ by a factor of five in hardness.

• Hydration

  Cement, lime and plaster set by reacting with water rather than by drying — which is why concrete hardens under the sea.

• Injection moulding

  Melt, inject, cool, eject — in seconds, identically, a hundred million times. How most plastic objects come to exist.

• Kraft pulping

  Dissolving lignin out of wood with sodium hydroxide and sodium sulfide — the dominant route to paper, and a chemical plant that runs largely on its own waste.

• Kroll process

  Reducing titanium tetrachloride with magnesium in a sealed vessel — slow, batch-wise, and still the only economic route to titanium metal.

• Mechanical recycling

  Sort, wash, shred, melt, re-pelletise. It works, it is the only route operating at scale, and it degrades the polymer a little every time.

• Metallothermic reduction

  Taking a metal out of its compound by offering a hungrier metal in exchange — the route to the elements carbon and electricity cannot reach.

• Molten salt electrolysis

  Passing current through a molten chloride or oxide to win a metal too reactive to smelt — the only route to magnesium, sodium, lithium and calcium.

• Neutron irradiation

  Making elements that barely exist in nature by feeding neutrons to ones that do — how plutonium is produced, and how everything past uranium is made at all.

• Polymerisation

  Joining small molecules into chains thousands of units long — the reaction that turns a gas into a solid and underlies every synthetic plastic.

• Pyrolysis

  Heating something without letting it burn — which drives off everything volatile and leaves the carbon behind.

• Quarrying

  Cutting stone out of the ground in usable pieces — the oldest extractive industry, and the step every building stone passes through.

• Rare earth separation

  Pulling seventeen nearly identical elements apart by solvent extraction, one faint preference at a time, repeated through thousands of stages.

• Roasting

  Heating a sulfide ore in air to convert it to an oxide — the step that makes zinc and lead smeltable, and historically the largest source of industrial sulfur dioxide.

• Rolling

  Squeeze it between rollers until it is thinner and longer. Most metal a person ever sees has been through this, and nothing else is remotely as cheap.

• Smelting

  Heating an ore with a reducing agent to separate metal from the elements it is chemically bound to.

• Solvent extraction and electrowinning

  Dissolving metal out of low-grade ore, moving it into a clean solution with an organic reagent, and plating it out with electricity — the route that made waste rock into copper ore.

• Steam cracking

  Heat hydrocarbons until they break, then freeze the wreckage before it reassembles. The single reaction the plastics industry rests on.

• Tanning

  Cross-linking the collagen in a hide so it will not rot — one of the oldest manufacturing processes there is, and still one of the dirtiest.

• Vapour deposition

  Building a solid layer out of a gas, an atom at a time — how every thin film is made, from a touchscreen electrode to a synthetic diamond.

• Vulcanisation

  Heating rubber with sulfur to link its molecular chains — the transformation that turned a sticky curiosity into an industrial material.

• Welding

  Join two pieces of metal by melting them into one — and create, in the few millimetres either side, a third material nobody chose.