Metal in design: the HART guide to metals, finishes and patinas

Metal is the material of permanence. A bronze handle polished by a hundred years of hands, a wrought-iron balustrade that has outlived the house it was made for, a brass tap slowly taking on the colour of its use: in a fine interior, metal is never neutral. It brings weight, cold or warmth to the touch, light, and a way of ageing that you either welcome or must anticipate.

This guide is written for those who specify, commission or simply want to understand what they are buying: the families of metals and how they behave, the finishes and patinas, how metal is worked, where each one belongs in a home, and how to look after it. For the craft itself, our guide to art metalwork and blacksmithing goes into the workshops.

A short history of metal in design

Bronze, gold and the first workshops

Bronze, an alloy of copper and tin, gave its name to an age. With it came the technique that still underpins art casting today: lost-wax casting, in which a wax model is encased in a mould, melted out and replaced by molten metal. The ancient world also gave us the hand techniques goldsmiths and metalworkers still use: repoussé, where the metal is pushed out from behind, chasing, which defines the design from the front, filigree and granulation. Gold, which neither tarnishes nor corrodes, was kept for gods and kings.

Iron, from the cathedral door to the royal gate

Iron took over from bronze for tools and structure, and the blacksmith became central to building. Gothic church doors carry wrought-iron hinges that spread across the wood like foliage, structure and ornament at once. The high point of French ironwork came in the eighteenth century: the gilded gates of Place Stanislas in Nancy, forged by Jean Lamour in the 1750s, remain the reference for what wrought iron can do when it is treated as lace.

The industrial century: cast iron, steel and aluminium

The nineteenth century turned metal into architecture. Cast iron, poured into moulds, made ornament repeatable: garden furniture, railings, columns, whole facades. Henri Labrouste’s reading room at the Bibliothèque Sainte-Geneviève (1851) showed that an iron frame could be noble. Bessemer’s process (1856) made steel cheap, and the Eiffel Tower (1889) put some 7,300 tonnes of puddled iron on show. At the turn of the century, Art Nouveau bent iron into plant forms, most famously in Hector Guimard’s Paris Métro entrances.

Aluminium followed the opposite path. Isolated in the 1820s, it was so costly to produce that Napoleon III reserved aluminium cutlery for his most honoured guests while the others ate from gold. The Hall-Héroult electrolytic process (1886) made it an industrial metal within a generation.

Modernism and the chromed tube

Modernism made metal domestic. In 1925, at the Bauhaus, Marcel Breuer bent steel tube into an armchair, reportedly inspired by his bicycle handlebars. Mart Stam’s cantilevered chair followed in 1926, and in 1928 Charlotte Perriand, Le Corbusier and Pierre Jeanneret designed the chromed-tube chaise longue that still bears their names. Stainless steel, invented in the 1910s, crowned the Chrysler Building in 1930 and became the gleam of Art Deco and Streamline Moderne.

After the war, mid-century designers made metal light. Harry Bertoia welded steel wire into the Diamond chair (1952), Eero Saarinen cast the Tulip base in aluminium to clear away what he called the “slum of legs”, and Charles and Ray Eames launched their Aluminum Group in 1958. In 1958 too, Poul Henningsen’s Artichoke lamp appeared with its copper leaves.

Today: the machine and the hand

Laser and water-jet cutting, CNC machining and metal 3D printing now allow forms no smith could have made. Joris Laarman’s Bone Chair (2006), cast in aluminium from an algorithm modelled on bone growth, and the 3D-printed stainless steel bridge his team installed in Amsterdam in 2021 mark that shift. At the same time, the most coveted pieces of collectible design are cast bronzes and hand-patinated surfaces. In high-end interiors, the machine has not replaced the hand: it has made the hand rarer, and therefore more precious.

The metal families

Every metal has a temperament: its weight, its colour, the way it reacts to air, water and hands. Here are the ones you will meet in a fine interior, and what each one is really for.

Wrought iron, cast iron and steel

Three materials that are often confused. Wrought iron, low in carbon and fibrous, is hammered hot and is the material of traditional gates and balustrades; true wrought iron is no longer produced industrially, and today’s “wrought ironwork” is generally forged mild steel. Cast iron, rich in carbon, is poured into moulds: heavy, rigid and brittle under impact, it is the material of radiators, stoves, garden furniture and Victorian columns. Mild steel is the everyday structural metal: strong, easy to weld and form, inexpensive, but it rusts as soon as it is left bare. In a fine interior, it is seen blackened, waxed, lacquered or powder-coated, rarely raw.

Stainless steel

Steel with at least 10.5% chromium, which forms an invisible, self-repairing oxide layer. Two grades matter in a home: 304 (18% chromium, 8% nickel), the standard for kitchens and indoor use, and 316, with added molybdenum, which resists chlorides and is the one to specify near the sea, around a pool or for outdoor fittings. Stainless steel is hygienic and durable, but not invulnerable: on the coast, 304 can show brown “tea staining”. Brushed, satin, mirror-polished or tinted black by PVD, it is the metal of the professional kitchen brought home, as our guide to noble kitchen materials explains.

Corten steel

A weathering steel whose surface rust stabilises into a dense, protective rust-brown patina. Magnificent on facades, planters and garden sculpture, it has two limits that are often forgotten: rainwater running off it stains stone and paving during the first years, and it does not stabilise in a salty or permanently damp atmosphere. It is an outdoor material; indoors, the same look is obtained with a varnished rust patina on ordinary steel.

Aluminium

About a third of the weight of steel, naturally resistant to corrosion, easy to cast, extrude and machine. It is the metal of outdoor furniture, joinery profiles and lighting. Its surface can be anodised, an electrochemical treatment that thickens the natural oxide layer and can be dyed (bronze, black, champagne), or powder-coated. Its limits: it is softer than steel and dents more easily, and a cast aluminium never has the depth of a cast bronze.

Copper

The warmest of metals, pink-orange when new, then brown, then, outdoors and over time, the green verdigris of old roofs. It is excellent at conducting heat, hence its place in fine cookware, and copper alloys are naturally antimicrobial. In interiors it appears on range hoods, sinks, lighting and splashbacks, and it marks with every fingerprint: choose it for its life, or have it varnished.

Brass and bronze

Both are copper alloys, and they are constantly confused. Brass is copper and zinc: golden, easy to machine and polish, the metal of door furniture, taps, light fittings and inlaid trims. Bronze is copper and tin: darker, harder and denser, the metal of art casting, sculpture, fine architectural hardware and furniture mounts. A rule of thumb: brass is turned and polished, bronze is cast and patinated. Unlacquered brass, the “living finish” now sought after in kitchens and bathrooms, darkens and softens with use; lacquered brass stays bright until the lacquer wears.

Zinc and pewter

Zinc is the material of Paris roofs, a grey that whitens and dulls over time, and of worktops and cladding with a soft, matt patina. Pewter, a tin-based alloy, is the metal of the traditional Parisian bistro counter, which the French still call “le zinc”. Both are soft, marked by use, and that is precisely their charm.

Titanium

Light, extremely strong and almost insensitive to corrosion, titanium is still rare in interiors because of its cost and the difficulty of working it. Its best-known appearance is architectural: the titanium skin of Frank Gehry’s Guggenheim Bilbao (1997). In design, it is used for limited editions and fine hardware, sometimes heat-coloured in iridescent blues and golds.

Gold, silver and gilt bronze

In decoration, precious metals are used above all as a surface. Gold leaf, beaten to a fraction of a micron, is laid by the gilder on wood, plaster or metal: water gilding, which can be burnished to a mirror shine, for frames and fine furniture; oil gilding, more matt and more resistant, for exteriors and ironwork such as the gates of Versailles. Silver leaf tarnishes and is usually varnished. Gilt bronze, the “bronze doré” of French furniture, dresses the mounts of cabinetmaking from Boulle to the Empire. It was historically fire-gilded with mercury, a process now abandoned for health reasons; today’s gilt bronzes are gilded by electroplating.

At a glance

Finishes and patinas

In a fine interior, the finish matters as much as the metal itself. The same brass can look like a jewel, an old ship’s fitting or a contemporary matt surface depending on how it is treated. There are three families of finish: mechanical, which work the surface itself; applied, which cover it; and chemical, which transform it.

Mechanical finishes

Polished to a mirror; brushed, with fine parallel lines that hide fingerprints and small scratches; satin or bead-blasted, a soft, uniform matt; hammered, where each blow of the hammer leaves a facet that catches the light. A hammered finish done by hand is irregular; when it is perfectly repetitive, it was stamped.

Applied finishes

Powder coating, a polyester or epoxy powder baked onto the metal, is the most durable coloured finish for steel and aluminium, inside and out. Electroplating deposits a thin layer of chrome, nickel, gold or brass onto another metal. PVD (physical vapour deposition), a vacuum-applied ceramic-metal coating, is now the reference for taps and hardware in brushed gold, bronze or black: far more resistant to wear than plating. Lacquer and wax protect without changing the colour, the first for longer, the second in a way that can be renewed by hand.

Patinas

A patina is the surface a metal takes on with time, or that a craftsperson gives it with chemicals, heat and hand work. Bronze foundries apply their patinas with a torch and a brush, layer after layer: brown, green, black, sometimes red or gold. Blackened steel, a deep grey-black obtained by oxidation, then waxed or varnished, is one of the signatures of contemporary high-end interiors. Each hand patina is unique; that is both its value and the reason why two batches never match exactly.

How metal is worked

Shaping

• Forging: the metal is heated and hammered on the anvil or under a power hammer. It is the gesture of the smith, which aligns the grain of the metal and gives the irregular vigour of hand-made ironwork.
• Casting: molten metal is poured into a sand mould for robust pieces, or a lost-wax mould for fine detail. All great bronzes, from sculpture to door handles, are cast.
• Spinning: a disc of metal is pressed against a rotating form on a lathe. Most fine lampshades and bowls in brass, copper or aluminium are spun.
• Sheet work: cutting, folding and bending sheet metal. Jean Prouvé built a whole language of furniture and architecture on folded sheet steel.
• Machining and cutting: CNC milling and turning, laser and water-jet cutting, for precision parts, perforated screens and fine joints.
• 3D printing: metal powder fused layer by layer, for complex geometries, still reserved for prototypes and limited editions.

Joining

Welding fuses the parts together; TIG welding, precise and clean, is the one used for fine visible work. Brazing and soldering join at lower temperatures with a filler metal, essential for brass and copper. Riveting and screwing leave the assembly visible and dismantlable: the bolts of Prouvé’s furniture are part of its beauty. A good piece of metal furniture can be judged by its joints: clean welds ground flush or deliberately expressed, never left in between.

Metal in the interior

Furniture

Tubular chrome for the modernist icons, blackened steel for the frames of contemporary tables and shelving, cast bronze for collectible pieces, brass for trims and feet. In high-end furniture, metal is often there to make another material sing: the bronze base under a marble top, the brass inlay in an oak veneer. Our guide to wood in design covers the other half of these pairings.

Architecture and ironwork

Staircases and balustrades, gates, steel-framed glazed partitions in the spirit of workshop windows, canopies, fireplace surrounds. These are made to measure by metalworkers, often in collaboration with the architect and the joiner. For a staircase or a balustrade, everything depends on the quality of the drawing, the finish and the installation: our metalwork guide presents the leading workshops.

Kitchens, bathrooms and hardware

This is where metal is touched every day. Brushed stainless steel for professional-style worktops and fronts, unlacquered brass or PVD for taps and handles, copper or zinc for hoods. In high-end kitchens and bathrooms, the rule is simple: one dominant metal, possibly a second as an accent, never three. Door furniture, the first thing a guest touches, deserves solid brass or bronze rather than plated zamak (a zinc alloy that is cheaper and lighter in the hand).

Lighting

Spun brass, folded aluminium, copper leaves, patinated bronze: metal shapes light by reflecting it. A polished interior gives a warm, golden light; a white lacquered interior a softer, more diffused light. Our designer lighting guide covers the houses that master these effects.

Choosing and caring for metal

Questions to ask before choosing

• Inside or outside? Outdoors, only stainless steel 316, powder-coated or anodised aluminium, bronze, copper and corten will last without constant attention. By the sea, rule out 304 stainless steel and corten.
• Touched daily or seen from afar? Handles, taps and worktops need a finish that tolerates hands: PVD, brushed stainless steel, or a living finish you have chosen to let age.
• Solid or plated? Solid brass and bronze can be repolished for decades. Plating on a base metal cannot.
• Which other metals are already in the room? Coordinate tones and finishes from the start rather than collecting them piece by piece.

Care, metal by metal

Stainless steel: a soft cloth, mild soap, and always in the direction of the brushing; never steel wool, which leaves particles that rust. Lacquered brass and PVD: water and mild soap only; any abrasive or metal polish will damage the coating. Unlacquered brass and copper: leave them to age, or polish with a dedicated product if you want the shine back. Waxed or blackened steel: dust, and renew the wax once or twice a year. Bronze: a dry cloth and occasional wax; never polish a patinated bronze, or you will remove the patina the foundry spent hours building.

Sustainability

Producing metal from ore consumes a great deal of energy, especially aluminium. But metals have one rare quality: most can be recycled again and again without losing their properties. Recycling aluminium uses around 5% of the energy needed to produce it from bauxite, and recycled steel and copper also need far less energy than primary metal. Specifying recycled content, where the supplier can document it, is therefore one of the simplest environmental decisions in a project. Certifications exist for sourcing: the Aluminium Stewardship Initiative for aluminium, the Responsible Jewellery Council for gold and silver.

The most sustainable metal, though, is the one you never replace. A solid bronze handle, a forged balustrade, a stainless steel worktop, a brass light that can be rewired and repolished: these last for generations, and can be restored rather than discarded. In metal as in everything, quality is the first ecological choice.

Frequently asked questions

What is the difference between brass and bronze?

Both are copper alloys. Brass is copper and zinc: golden, easy to machine and polish, used for hardware, taps and lighting. Bronze is copper and tin: darker, harder and denser, used for art casting, sculpture and fine architectural hardware.

Which metal is best for outdoor use?

Stainless steel 316, powder-coated or anodised aluminium, bronze and copper all perform well outdoors. Corten works inland but not by the sea. Untreated mild steel and 304 stainless steel should be avoided in coastal areas.

What is a living finish?

A living finish is a metal left without lacquer or coating, usually brass or copper, so that it darkens and develops a patina with use. It is chosen for its character; if you want the colour to stay as new, choose a lacquered or PVD finish instead.

Is PVD better than plating?

For surfaces that are touched every day, yes. PVD is a very thin ceramic-metal coating applied under vacuum; it resists wear and scratches far better than traditional electroplating, which is why the best tap and hardware makers use it for their gold, bronze and black finishes.

Continue with materials

• 01Fine craftsArt metalwork and blacksmithingThe craft, the workshops and how to commission a balustrade, a gate or a piece of furniture.→
• 02MaterialsWood in designSpecies, veneers and finishes: the other noble material of the interior.→
• 03MaterialsTextile materialsFrom silk to horsehair, the fibres of fine upholstery explained.→
• 04HubAll materials and finishesEvery HART guide to the materials of the fine interior.→