Ceramics In Watchmaking: What They Are, Why They’re Used, And Why They’re Tougher Than You Think
Ceramics for most of history were fragile and delicate. Modern engineering ceramics changed all that, and watchmaking has never been the same.
Making ceramic watches is a fairly new phenomenon, and with good reason.
Nobody knows when the first ceramics were made, but the first evidence we have of pit fired clay vessels is from around 20,000 years ago. Ceramics were not even remotely viable as cases for watches for most of that time (although ceramics were used as components for clock cases) for reasons all too obvious to anyone who has dropped a favorite mug onto a tile kitchen floor, but starting in the early 20th century, a new class of ceramics were developed which eventually made it possible to use ceramics for watch cases, bracelets, and dials, beginning in the 1960s.
Rado produced the Diastar, with a “hardmetal” case starting in 1962 – the case was made of tungsten carbide, which fits the technical definition of a so-called engineering or technical ceramic. In the 1970s, Omega and Tissot experimented with ceramics in very small numbers. IWC pioneered the creation of ceramic watches in the post-quartz era early – starting in 1986, in the Da Vinci line (and this was also the same year the Rado Integrale came out; the first watch with both a ceramic case and bracelet). Since then ceramics have transformed watchmaking, becoming the first real alternative to traditional precious metals and stainless steel in the history of horology.
What Are Ceramics, And How Are They Different From Metal Alloys?
Ceramics are defined partly by their chemistry, but also partly by how they’re made.
A ceramic in the broadest sense of the word, is any solid non-metal material with a regular internal crystal structure. The atoms in a ceramic are arranged in a repeating lattice, with the atoms held together by covalent bonds in which electrons are associated with specific atoms. Glasses do not have a regular crystal structure. Metals have electrons which flow freely through the crystal structure.
These basic differences give the different materials their particular properties. Metals are generally conductors, which readily conduct heat, and which are malleable. Ceramics, on the other hand, are generally insulators, and are rigid. The two materials respond to physical stress differently as well; metals bend, while ceramics are brittle and will suddenly fracture if they’re subjected to strong enough mechanical forces.
Ceramics are also usually quite hard, so much so that they have to be machined with diamond coated machine tools. Metals are much easier to machine, as a rule, although some metals are much harder than standard stainless steels to work with (tantalum is a case in point).
Finally, ceramics are usually first molded into a desired shape, and then fired to set the final shape and to determine the final materials characteristics of the ceramic.
A key point to bear in mind is that the high tech ceramics used for watch cases are nothing like clay ceramics. They are generally made of a metal combined with another chemical element, and are used in some of the most demanding environments in engineering, including rocket and jet engines, biomedical applications (like joint replacements) and they’re also used for high wear components like ball bearings (the watch industry has been using ceramic ball bearings for automatic winding systems for decades). Ceramic watches are a logical outcome of the evolution of technical ceramics.
Because the definition of ceramics is partly one of exclusion (any non-metal with a regular crystal lattice structure) the term is a very broad one, and it fits some materials you wouldn’t usually think of as ceramics. This includes, for instance, synthetic rubies, such as the ones used in watch movements; they are an aluminum oxide and although we don’t generally think of them as ceramics, they nonetheless fit the definition.
- Ceramics used for ceramic watches are not clay; they’re high tech composites
- Ceramics are for all intents and purposes, scratchproof
- Ceramic colors are permanent and will never fade
- Ceramics used for watch cases, are almost indestructible compared to clay ceramics
- Ceramics however, don’t bend like metals; a hard impact can cause cracks or chips
Why Ceramic Cases And Bezels Are More Durable Than You Think
Ceramics can be oxides, nitrides, or carbides, which are combinations of metals with oxygen, nitrogen, or carbon. The most popular ceramic for watch cases is zirconium oxide, which is a combination of zirconium (a metal) with oxygen. Zirconium oxide makes an excellent case material for all the usual reasons cited for ceramics (corrosion resistance, hardness, lightness, and strength) and it has another property which makes it especially suitable for cases and bezels.
Zirconium oxide has a type of resistance to cracking called “transition toughening.” If a crack starts to form, the crystals at the tip of the crack change their shape, which produces a compression force at the tip of the crack. The more the crack widens, the stronger the force working to close it, and this often seals up the forming crack completely. For this reason, ceramic cases and bezels made of the material are far less prone to cracking or shattering than you would expect from a ceramic material.
Zirconium dioxide is the most common ceramic for watch cases and bezels, thanks partly to its ability to heal cracks before they can spread.
How Ceramic Cases Are Made: Zirconium Oxide
Making cases out of zirconium oxide usually starts with a fine powder of the material, and the size of the individual particles can make a big difference in the physical characteristics of the finished product. Ceramic powder, consisting of nanometer scale grains, is mixed with a binder and pressed or injected into the mold. Once compressed into the right shape, the ceramic is unmolded and placed in a kiln to fuse the particles permanently together, during which time the binder burns off. This process is called sintering.
As a result of this, and also of the consolidation of the individual particles, a case may shrink up to thirty percent. The degree of shrinkage can be controlled by carefully monitoring temperature and the size of the ceramic powder grains but some final finishing – with diamond tools, which are necessary thanks to the hardness of the ceramic – may be required to reach the exact dimensions specified.
A Note On Ceratanium From IWC
IWC introduced Ceratanium in 2017 in the Aquatimer Perpetual Calendar. Ceratanium is a material which has properties of both ceramics, and metal alloys.
The alloy is a combination of titanium and zirconium, and, as IWC’s head of design, Christian Koop, says in the above video, it can be machined and finished like any metal alloy. Once the case has been machined and finished, it then goes into a kiln with a high oxygen atmosphere. Once the temperature is high enough (around 1600º Celsius) the oxygen atoms diffusing into the case metal form an oxide with zirconium – zirconium oxide, in other words.
This material combines the manufacturing advantages of a metal alloy, with the scratch resistance, toughness, and biocompatibility of ceramics. The machinability of ceratanium means it can be used for smaller components as well, including crowns and chronograph pushers.
- Do ceramic watches scratch? Very seldom. Some very hard tool steels, diamond, and some industrial abrasives can scratch ceramics.
- Are ceramic watches lighter than stainless steel? Yes – about 30% lighter.
- How is a ceramic watch made? Fine powder is pressed into a mold, and then fired in a kiln to fuse the ceramic particles.
- What is the difference between a ceramic bezel & case? Both are made of the same materials; ceramic bezels can have markers filled with Super-LumiNova for low light visibility.
- Do ceramic watches fade or change color over time? No. The colors of ceramic watches and bezels are permanent and cannot fade over time.
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