The Bench · N° 12

Steel, silicon and Nivachron hairsprings compared

Hairspring materials affect magnetism, temperature behaviour, manufacture and repair. Their geometry and adjustment still matter as much as the material name.

Hen & Mills Editorial · 4 min read · 19 August 2026

The hairspring controls the rhythm of a mechanical watch with the balance wheel. Its material must remain elastic through millions of cycles while resisting temperature change, magnetism, shock and ageing.

Traditional watchmaking uses metal alloys. Silicon introduced a very different manufacturing method and strong resistance to magnetism. Nivachron is a modern titanium-based alloy developed to improve magnetic and thermal performance while retaining a metallic spring.

None of the three can be judged from material alone. Shape, attachment and adjustment determine how it works in a movement.

What the hairspring does

The balance wheel rotates in one direction, the hairspring tightens and then pulls it back. The pair forms an oscillator with a natural frequency.

A change in the spring's elasticity or effective length changes that frequency and therefore the watch's rate.

The spring is extremely light and fine. Small contamination, deformation or magnetic attraction between coils can have a large effect.

Traditional steel-alloy springs

Modern metallic hairsprings are not simple untreated steel. Specialist iron-nickel and related alloys were developed to reduce sensitivity to temperature and improve stability.

They can be formed into flat spirals or overcoils, adjusted at the bench and paired with many regulating systems. Watchmakers have extensive experience handling them.

Their main practical weakness is that ferromagnetic alloys can be affected by sufficiently strong magnetic fields, although alloy formulation and movement protection vary.

What magnetism does

If adjacent coils become magnetically attracted, part of the spring can effectively shorten. The movement may then run very fast or behave irregularly.

A magnetised watch can often be demagnetised without dismantling the movement, provided no other fault is present. Repeated exposure may still be inconvenient.

Material is only part of magnetic resistance. Case construction, movement components and the strength and direction of the field also matter.

Silicon hairsprings

Silicon hairsprings are made using microfabrication processes rather than drawn as wire and coiled by hand. Their geometry can be produced with high precision and repeated across large batches.

Silicon is not ferromagnetic, resists corrosion and can be shaped with integrated terminal features. It is also light, which can help reduce sensitivity to shock.

The material is brittle rather than ductile. If a silicon spring chips or breaks, it normally needs replacement; reshaping is not practical.

Temperature and silicon

Raw silicon's mechanical properties change with temperature, so watchmaking springs use design features, material treatment or composite structures to control the effect.

Different manufacturers have developed their own solutions and patents. It is therefore too simple to say that every silicon hairspring is automatically temperature neutral.

The performance claim belongs to the complete oscillator and the way the material has been engineered.

Nivachron

Nivachron is a non-ferromagnetic titanium-based alloy developed by the Swatch Group and Audemars Piguet. It is intended to reduce the influence of magnetic fields and temperature compared with conventional hairspring alloys.

Because it remains metallic, it can support production and adjustment methods familiar from metal springs, though its exact handling belongs to trained specialists.

Its presence indicates a modern material choice. It does not reveal the terminal geometry, balance design or level of regulation.

How damage is handled

A skilled watchmaker can sometimes straighten or reform a damaged metallic hairspring, particularly in a vintage watch where replacement parts are unavailable. That work is delicate and not always economical.

Silicon parts are normally replaced as components or complete balance assemblies. Access then depends on the manufacturer's parts policy.

A modern metal spring may also be supplied only as an assembly, so theoretical repairability does not guarantee practical access.

Geometry remains critical

A perfectly chosen material can still perform poorly if the spring is off-centre, out of flat, touching another component or badly attached.

Flat spirals, overcoils and shaped terminal curves manage how the spring breathes. Free-sprung and indexed balances regulate rate in different ways.

These details affect positional performance and stability. The material name cannot substitute for correct geometry.

Manufacturing consistency

Microfabricated silicon can provide highly repeatable shapes. Industrial production of metal springs has also become exceptionally controlled, with precise forming, heat treatment and sorting.

Consistency helps manufacturers assemble and regulate movements efficiently. It does not remove the need to test the completed oscillator in several positions and states of wind.

A watch's stated accuracy is better evidence of the final result than a photograph of the spring.

Shock and everyday use

Hairsprings sit within a shock-protected balance assembly, but a strong impact can still disturb an attachment, deform metal or damage a brittle component.

No current material makes the oscillator immune to careless handling. If a watch changes rate suddenly after a knock, it should be checked.

For normal wear, movement design and service support may matter more than choosing a spring material from a specification list.

Which one is better?

Silicon offers strong magnetic resistance, repeatable geometry and low mass. Modern metal alloys such as Nivachron improve resistance while retaining metallic behaviour. Established steel-alloy systems are widely understood and can perform to very high standards.

The best choice depends on the movement's design, expected magnetic environment and service network.

A material should be credited for the problem it solves, not treated as a quality ranking for the whole watch.

What to ask instead

Look for the watch's tested magnetic resistance, stated rate and service arrangements. Ask whether the spring or balance assembly will remain available for the expected life of the model.

Consider whether independent repair access matters to you and whether the manufacturer publishes meaningful performance data.

The hairspring material is an interesting part of the answer. The complete oscillator, and the support behind it, determine what you will experience.