Every era of engineering has been shaped by the materials available to it. Bridges, ships, engines, buildings, vehicles and consumer products are designed around what materials can do, what they cost and how reliably they can be supplied. Over the last three centuries, a series of breakthroughs in making materials, rather than discovering them, changed what engineers could build: iron smelted with coke, steel made in bulk, aluminium refined by electricity, plastics created by chemistry and timber engineered into consistent products.
These changes rarely happened because a new material was simply better. Some were forced by scarcity. Some came from outsiders who were not committed to existing processes. Many depended on making properties reproducible and guaranteed, so that engineers could design with confidence and buyers could hold suppliers to a specification. Each brought new risks as well as opportunities.
This article traces how iron, steel, aluminium, plastics and engineered timber became the materials of modern industry, and draws out lessons for manufacturers and engineers today about material substitution, process innovation, specification, supply and sustainability. It is general information for engineers, buyers, product developers and managers.
Iron: a resource crisis and a substitution
For centuries, iron was smelted using charcoal. Charcoal worked well, but making it consumed forests. In Britain by the seventeenth century, the loss of woodland had become a strategic concern, threatening timber needed for ships. Ironmakers needed another fuel.
Coal contains impurities that spoil iron, and early attempts to use it failed. In 1709, Abraham Darby at Coalbrookdale in Shropshire succeeded in smelting iron with coke, coal baked to drive off impurities, at commercial scale. Coke iron was not adopted because it was better than charcoal iron; it was adopted because charcoal was becoming unavailable. Over the eighteenth century, coke smelting spread, and production rose as the demand for iron grew, much of it driven by steam engines that themselves needed iron.
Other developments followed:
- John Wilkinson’s boring mill of 1774 made large cylinders accurate enough for efficient steam engines.
- Henry Cort’s puddling process and grooved rolling mills of the 1780s produced wrought iron, tough and workable, from pig iron in larger quantities.
- In 1779, the Iron Bridge at Coalbrookdale, the first major bridge built of cast iron, showed iron’s potential for structures.
Steel: from luxury to bulk material
Before the 1850s, steel, iron with a controlled amount of carbon, combining strength and toughness, was expensive and made in small quantities. Large structures used cast iron, strong in compression but brittle in tension, or wrought iron, tough but laborious to make and variable.
In 1856, Henry Bessemer, an inventor from outside the iron industry, patented a process that blew air through molten pig iron. Oxygen burned out carbon and other impurities, and the heat from these reactions kept the metal molten without additional fuel. A batch that would have taken skilled puddlers hours could be made in minutes. Steel became a bulk material.
Problems remained, and their solutions show how chemistry came to matter:
- Phosphorus in many iron ores made Bessemer steel brittle. In 1878, the cousins Sidney Gilchrist Thomas and Percy Gilchrist developed a basic lining for converters that removed phosphorus, unlocking vast ore deposits, especially in continental Europe.
- Regenerative furnaces, developed by the Siemens brothers, recovered heat from exhaust gases to preheat incoming air, reaching higher temperatures. The resulting open-hearth process was slower than Bessemer’s but allowed the steel’s composition to be sampled and adjusted, producing more consistent steel.
- Alloy steels, made by deliberately adding elements such as manganese, chromium, nickel and tungsten, gave steels with specified properties for tools, armour and machinery. In 1913, Harry Brearley in Sheffield developed a chromium steel that resisted corrosion, an early stainless steel.
Over the twentieth century, basic oxygen steelmaking and electric arc furnaces, which melt scrap steel, replaced earlier methods. In Australia, BHP opened its Newcastle steelworks in 1915, beginning large-scale domestic steelmaking.
Aluminium: electricity makes a metal cheap
Aluminium is the most abundant metal in the earth’s crust, but it is bound tightly in compounds and is hard to extract. In the mid-nineteenth century, it was more expensive than silver and was used for luxury items.
In 1886, Charles Martin Hall in the United States and Paul Héroult in France independently discovered that aluminium could be produced by passing an electric current through alumina dissolved in molten cryolite. Combined with the Bayer process for refining bauxite ore into alumina, developed shortly afterwards, the Hall–Héroult process made aluminium cheap enough for widespread use. It depended on large amounts of electricity, so aluminium smelters located near cheap power.
Aluminium’s lightness and corrosion resistance made it essential in aircraft, transport, packaging, construction and electrical conductors. Australia became one of the world’s largest producers of bauxite and alumina. Recycling aluminium needs only a small fraction, often cited as about 5%, of the energy needed to make it from ore, which makes recycling especially valuable.
Plastics: materials designed by chemistry
Plastics are polymers: long chain molecules, mostly built on carbon. Early plastics were based on natural materials: Alexander Parkes patented a mouldable material made from cellulose in 1856, and celluloid followed. In 1907, Leo Baekeland created Bakelite, the first fully synthetic plastic, a hard, heat-resistant thermoset used for electrical insulators and housings.
Through the twentieth century, chemists developed polymers with designed properties: nylon in the 1930s, and polyethylene, PVC, polystyrene and others that became the basis of packaging, consumer goods, pipes, medical devices and engineering components. Injection moulding made complex plastic parts cheaply in huge numbers.
Plastics brought new challenges: properties that change with temperature and time, flammability, recycling difficulty and environmental persistence. These are now driving work on recycled, bio-based and more easily recycled polymers.
Engineered timber: consistent wood
Timber is a natural material whose strength varies with species, growth, knots and moisture. Engineered wood products make it consistent and allow larger, more efficient structures:
- Plywood, bonded layers of veneer with alternating grain directions, began commercial production in the early twentieth century.
- Glued laminated timber, or glulam, bonds layers of timber into large beams and arches.
- Cross-laminated timber, panels made of layers glued at right angles, developed in Europe from the 1990s and now used for multi-storey buildings.
Engineered timber turned a variable natural material into products with specified, graded properties that engineers can design with, and it offers lower embodied carbon than many alternatives when sourced sustainably.
Concrete: an ancient material reinvented
Concrete is one of the oldest engineered materials. The Romans made durable concrete from lime and volcanic ash, called pozzolana, and used it in harbours, aqueducts and great domes. Much of that knowledge was lost after the empire declined.
Modern concrete began with Portland cement, patented by Joseph Aspdin in England in 1824 and improved over the following decades. Concrete is strong in compression but weak in tension, so on its own it suits walls, foundations and arches. In the second half of the nineteenth century, builders and engineers such as the French gardener Joseph Monier began embedding iron and later steel bars, creating reinforced concrete, in which steel carries tension and concrete carries compression. In the early twentieth century, Eugène Freyssinet and others developed prestressed concrete, in which steel tendons are tensioned to put the concrete into compression before it is loaded, allowing longer, slimmer spans.
Concrete is now the most widely used construction material in the world. Cement production is also a major source of carbon dioxide emissions, which is driving the use of supplementary materials such as fly ash and slag, new cement chemistries and more efficient structural design.
Composites and advanced materials
Through the twentieth century, engineers combined materials to get properties neither could provide alone. Glass fibre reinforced plastics made light, corrosion-resistant boats, tanks and panels. Carbon fibre composites, developed into high-performance materials from the 1960s, offered exceptional strength and stiffness for their weight and moved from aerospace and racing into sporting goods, wind turbine blades and industrial equipment. Titanium alloys, technical ceramics and engineered polymers served demanding applications.
These materials brought new challenges: complex manufacturing, difficult inspection, repair methods different from those for metals, and recycling problems that are still being solved. Additive manufacturing has added further options, building parts from metal and polymer powders with properties that depend heavily on the process, so qualification and testing are especially important.
From found properties to specified properties
A common thread runs through all these stories. A material becomes an engineering material when its properties become reproducible and guaranteed. Wrought iron varied with each puddler’s work; timber varies with each tree. Modern materials come with standards, grades, test methods and certificates, so a designer can use a number in a calculation and a buyer can hold a supplier to it. The choosing metals for engineered parts article explains how to specify materials by standard, grade and condition today.
Lessons for engineers and manufacturers today
Substitution is often forced, not chosen
Coke replaced charcoal because forests were running out. Today, material substitutions are often driven by supply disruption, price spikes, regulation or sustainability targets rather than by technical superiority. Substitutes may be inferior at first and need engineering to make them work.
Process innovation creates markets
Bessemer steel and Hall–Héroult aluminium succeeded because new processes slashed costs, not because the materials were new. Cheaper processes open uses that were previously uneconomic. Manufacturers should watch for process changes in their supply chains that could change the economics of their products.
Outsiders can see what insiders cannot
Bessemer and Gilchrist Thomas came from outside the iron industry and were willing to discard existing processes. Established businesses can benefit from outside perspectives, while recognising that outsiders usually need the industry’s knowledge and capital to scale.
Chemistry and impurities matter
The phosphorus problem in steel shows how small amounts of impurities can decide whether a material works. Material specifications, certificates and incoming checks protect against variation that is invisible to the eye.
New materials bring new risks
Brittle cast iron in tension, phosphorus embrittlement, plastic creep and environmental persistence all appeared as materials were used in new ways. Qualifying new materials before committing to them is essential; the qualifying recycled materials for real products article explains how.
Location and supply security matter
Aluminium smelters located near cheap electricity, and steelworks near coal, ore and ports. Material industries still depend on energy, raw materials and transport, and disruptions in any of them ripple through to manufacturers. Understanding where critical materials come from, and holding qualified alternatives or buffer stock for the most important ones, reduces exposure to supply shocks.
Recycling and embodied carbon now shape choices
Steel and aluminium are highly recyclable, and recycling saves much of the energy of primary production. Material choices increasingly consider embodied carbon, recyclability and product life, as well as cost and performance.
A worked example
This is an illustrative example. A manufacturer of food processing equipment uses grade 316 stainless steel for a frame that must resist corrosion from cleaning chemicals. After a period of steep price rises and long lead times for 316 plate, the business reviews alternatives.
Options considered.
- Continue with 316, accepting higher cost and longer lead times.
- Use grade 304, cheaper but less resistant to chlorides in the cleaning chemicals; rejected after testing showed pitting risk.
- Use duplex stainless steel such as 2205, with chloride resistance at least as good as 316 and roughly twice the yield strength, allowing thinner sections where strength governs the design.
Engineering check. The engineer notes that stiffness, not strength, governs parts of the frame, and that all stainless steels have similar stiffness, so thinner duplex sections can be used only where strength governs. Members governed by strength are reduced in thickness; those governed by deflection keep their size. Welding procedures are qualified for duplex steel, which needs care to keep its properties.
Result. The redesigned frame, after review by the customer’s hygiene and quality staff, uses about 20% less material by weight than the original 316 design, offsetting much of duplex steel’s higher price per kilogram, and the business gains a second qualified material that reduces dependence on one supply. As with coke iron three centuries earlier, the substitution was prompted by supply pressure and made to work by engineering.
Applying these lessons in an Australian business
- Review material risks: supply, price, regulation and sustainability.
- Qualify substitutes before they are needed.
- Watch process changes in your supply chains.
- Specify materials by standard and grade, with certificates.
- Check chemistry and properties for critical parts.
- Consider recyclability and embodied carbon in material choices.
- Seek outside perspectives on long-established processes, including from suppliers and researchers.
Questions worth considering
- Which of our materials could become scarce, expensive or restricted?
- Have we qualified an alternative for our most critical materials?
- Which properties of our materials do we rely on, and are they guaranteed?
- Are there process changes in our industry that could change our costs?
- How do our material choices affect product life, recycling and carbon?
Bringing it together
Coke iron, bulk steel, aluminium, plastics and engineered timber transformed what engineers could build because new processes made them cheaper and their properties reliable. Their history shows that substitutions are often forced, that process innovation creates markets, that outsiders can unlock change, that impurities and chemistry matter and that new materials bring new risks. For manufacturers today, the practical lessons are to manage material risks, qualify substitutes, specify materials precisely and weigh recyclability and carbon alongside cost and performance.
Source: KEVOS editorial notes, drawing on an earlier KEVOS engineering history series on iron, steel, modern materials and engineered timber, together with established histories of technology. The worked example is illustrative. This article is general information.
