The enigma of ceramic

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The enigma of ceramic - Ceramic
4 minutes read
Ceramic is a very versatile material, but it is not without its Achilles’ heel. Here is an overview of a material that has seduced the watch industry.

Ceramic is everywhere, but it’s not always easy to see. It is certainly one of the most “in vogue” materials currently used in watchmaking. Its qualities are highly prized by the dozens of brands that use it. But behind all the hype lies an entire world of different materials that can be utilised in different ways. Although there are many advantages, the few disadvantages should nevertheless not be discounted.

The material known as ceramic, which made its watchmaking début in the 1980s, in fact includes a number of different materials. First of all, this is not the same kind of ceramic you’ll find in your kitchen cupboard: it’s high-tech ceramic. There are a several types, which share a number of qualities, and it is these qualities that have made them so popular. Among the ten or so different materials used, aluminium oxide (Al2O3) and zirconium oxide (ZrO2) are the most common. Acid cannot attack them, which makes them immune to oxidisation. They are highly abrasion resistant, so no more of those unsightly scratches that age watch cases prematurely. And they are extremely hard, which makes them resistant to deformation. These three points are what have made ceramic such a successful material for watch cases. But ceramic has been a feature of watch movements for a long time: many rotors rotate on ceramic ball bearings (and they make a very distinctive sound). But that’s not all. IWC’s new 52000 calibres use ceramic gears as part of the automatic winding mechanism, which is highly sensitive to friction.

IWC Ingenieur Automatic Edition AMG GT

It’s often said that ceramic is indestructible, but that’s only partly true. Indeed, the manufacturing process of ceramic, and the material’s very advantages, make it susceptible to breaking. Technical ceramics begin life as a powder, which is pressed into a mould. Because the powder melts at an extremely high temperature, it is not possible to pour the molten material into a mould, as is the case for metals. Instead, ceramic is sintered: when subjected to heat and pressure, the grains of powder melt partially on the surface, where they stick together, forming a relatively porous but homogeneous matrix. The advantage of this is that the already light material does not occupy the entire volume of the component, leaving air pockets that make the material even lighter still. The density of aluminium oxide is 3.9 g/cm3, compared with around 4.5 for titanium. The other side of the coin is that these microscopic cavities can form internal fault lines.

And let’s not forget that ceramics are extremely hard, which can be too much of a good thing. Its structure has no flexibility, which means that it is unable to absorb shocks. It just breaks. In practical terms, this means that you can happily scrape your watch against rocks, and nothing will happen. If you drop it, the case will survive. But if you were to throw it, there’s a risk that it will break. Its properties are virtually the opposite of steel, which helps to explain why ceramic is so difficult to machine. Being extremely hard and fragile, it reacts badly to the constraints imposed by machining tools. The moulding and firing stage is therefore crucial, because any mistakes can be extremely costly to rectify.

The other advantage of ceramic, however, is that it is a team player. It can be combined with other materials, which change its properties. Richard Mille, for example, uses TZP ceramic, a zirconium dioxide stabilised with yttrium oxide to make it more resistant to shocks. Hublot uses a porous skeleton of boron carbide, into which pure gold is injected. By mass, the proportions are 25%/75%, which means this unique alloy can be legally termed 18-karat gold. It is both precious and scratchproof, which is perhaps why they call it Magic Gold.

Richard Mille RM 07-01 Ladies

Another way of exploiting the benefits of ceramic is by inducing a chemical reaction on an aluminium case. Panerai has done just this, with a material it calls Composite. The case is aluminium, except on the surface, where the metal is oxidised in a vacuum. The aluminium is thus converted into aluminium oxide, the most common form of ceramic, which is scratchproof. The problem is that the case retains the advantages and disadvantages of its original material: it’s light but malleable, which means that it is prone to dents. One final interesting example comes from Jaeger-LeCoultre, which makes cases from Cermet, a “metallic ceramic”, which consists of a metal framework (titanium), strengthened with ceramic.

Jaeger-LeCoultre Deep Sea Chronograph Cermet

Ceramics have ergonomic and aesthetic advantages too: they are smooth to the touch and are good thermal insulators. In summer, this means that ceramic cases remain cool, unlike titanium or steel watches, which tend to heat up in the sun. Most ceramics are naturally black, a popular colour with watchmakers. And unlike surface treatments like PVD and DLC, the colour is permanent, and won’t degrade with wear or age. Other ceramics are naturally white, like the variant used by Chanel for its perennial favourite, the J12, and still others are chocolate-coloured. Ceramic can also be dyed in the mass, like the blue and green models we have seen from Bell&Ross. In fact, they use the same production facilities as Chanel.

Bell & Ross BR03-92

 

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