A variation of ceramic materials, zirconium oxide (ZrO2) is also called zirconia and this is the preferred form of ceramic used in watchmaking thanks to its resistance to crack propagation. Due to its propensity for high thermal expansion, it is often combined with steel to produce metallic alloys that boast the scratch-resistant characteristic of ceramic.
Zirconia is extremely hard and practically impervious to scratches, being three or four times harder than steel. It also does not age with time, maintaining its smooth, near-friction free surfaces for long periods of time. On the other hand, zirconia is completely rigid, unlike metals which are malleable. Thus, when struck at the appropriate angle with the appropriate amount of force, it will break.
Ceramic watch parts are manufactured by a sintering process, which is essentially compressing the material in powder form at high pressure and heating at high temperature until it solidifies. When it cools, the material has a tendency to shrink; the manufacturing process of ceramic components is very complex due to the sensitive nature of the raw material and the extremely precise engineering required during the sintering process. Unlike metals, they cannot be finished or reshaped after production, so every ceramic component has to emerge perfectly made. This is the main reason why it’s typically a very difficult undertaking to produce ceramic components in non-standard forms.
Ceramic is an ideal material for watch cases because this material remains pristine over the years. Predominantly forged in either black or white due to the complexity of the colouration process, ceramic components don’t just protect the watch but also impart a modern and industrial-chic aesthetic that’s all the rage in the 21st century. Yet, there are more ways to utilise this amazing material than just to produce a standard watch case, as evinced by Franck Muller’s 25th Anniversary Cintrée Curvex—ceramic can also be used creatively especially if you have the right idea.