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Is that dial enamel, porcelain, ceramic, or all of the above?

Is that dial enamel, porcelain, ceramic, or all of the above?

Buffy Acacia

A great thing about being a watch enthusiast in the internet age is that we can obsessively research anything we want. There are very few technologies which we can’t understand through Wikipedia, and many histories which you don’t need to trawl through books to find. However, not everything is as logical as a machine or as linear as history. Getting into the weeds of language and terminology, things can get messy. When it comes to admiring artful enamel, porcelain and ceramic dials, how can you tell which is which? And it doesn’t help that traditional porcelain crafts are often decorated with enamel, too. Let’s see if we can find exactly where this confusion stems from, and how you can tell the difference.

The meaning of enamel, porcelain, and ceramic

patek philippe world time 5231g dial close up

Let’s break down the exact definitions in use. Enamel is a vague term that can almost refer to any hard, shiny surface, from the outer layer of our teeth, to nail polish, to paint. That’s the first problem which makes things confusing, because just saying ‘enamel’ isn’t specific enough. When we refer to enamel as a decorative technique, it is almost always referring to something called vitreous enamel. The process involves firing powdered glass called frit until it melts, creating a glossy and strong surface with a beautiful depth of colour. It usually takes several applications to get a perfectly smooth finish, and there are many different techniques that can be used for varying effects. The most confusing part? Vitreous enamel is also known as porcelain enamel, which can sometimes be shortened just to porcelain. Grand Feu enamel is also just another term for vitreous enamel.

Seiko Presage Craftsmanship Series Arita Porcelain SPB445 dial

Unlike the misleading ‘porcelain enamel,’ true porcelain is a kind of ceramic that’s made from firing specific kinds of clay, most often containing a mineral called kaolinite. It’s similar to other clay earthenware such as terracotta that has been used in pottery for thousands of years, except that it’s fired at higher temperatures, and the formation of the mineral mullite (AKA porcelainite) leads to a much more dense and smooth product. Porcelain doesn’t require a glaze to protect it against water or other chemicals, although glazes are often used for decoration. While it is a ceramic, it is distinctly different from the zirconium oxide ceramics we usually see used in watchmaking, for example on the dial of the laser-etched Omega Seamaster Diver 300M collection.

Even the definition of ceramics is vague. They’re described as any heat and corrosion-resistant materials made by firing non-metallic compounds at high temperatures. Technically, even vitreous enamel fits that bill, but it certainly wouldn’t be labelled a ceramic. Zirconium oxide has become the common choice in watchmaking for ceramic cases and dials, mainly due to its high scratch resistance and pure white base colour. It’s also far stronger than something like porcelain, which would easily shatter if it were turned into a watch case.

Enamel’s history and techniques

Enamel Cloisonné 13th 14th century
Cloisonné enamel from the 13th-14th Century, Paris.

The history of enamel is utterly fascinating, and you could spend forever tracing its occurrences around the world. The oldest example of enamel is from a collection of Mycenaean rings that were uncovered from a tomb in Cyprus, dating back to the 13th century BC. From there enamel spread with imperfect techniques across Egypt and the Caucasus, before the ancient Celts of the 1st millennium BC started to hone the craft. One of the biggest problems with ancient enamel was the difficulty of melting the powdered glass without melting the host material, which was often gold, silver, or bronze. Over the next 2,000 years the art form spread wildly, prized both for its beauty, and the fact that it was cheaper than using precious gemstones to add colour.

Champleve Enamel Louvre Cupid king Heraclius copy
Champlevé enamel over gilt copper depicting a cherub, Emperor Heraclius of the Eastern Roman Empire, and the submission of Khosrau II of the Sasanian Empire, c.1160-1170.

We now have an established vernacular for the various techniques of vitreous enamel. Cloisonné is the oldest, where raised bars or wires of metal would be used as barriers to keep the enamelled areas separate. Champlevé enamel is when you start with a flat sheet of metal, and then carve a relief into it, creating individual reservoirs for the enamel. Champlevé allows for much more detail and complexity than cloisonné, although it can lack definition from a distance. One of the most sought-after and collectable forms of enamel is painted enamel, where the powdered mixture is suspended in a liquid and then painted onto the surface by hand. It takes an incredible amount of skill to ensure that the final product is perfect with no blurriness or colour bleeds. Painted enamel however shouldn’t be confused with enamel paint, which is just regular paint that dries to a glossy finish.

Enamel as a clock and watch staple

18th century clock enamel dial
An 18th century French clock with a classical enamel dial.

Throughout the history of clock and watchmaking, most components were just made out of metal. Usually it was brass, but occasionally it would be something precious like silver or gold. During the 1600s and 1700s, the use of vitreous enamel began to spread for white, cream, and black dials with contrasting Roman numerals. That pretty much solidified the identity of clocks and watches for the next 300 years. After the background colour is applied, enamel paint is stamped onto the dial before a final firing. When enamel paint is fired on enamel, the two layers fuse together as a single object.

The durability of enamel

Painted enamel floral pocket watch
A 17th century pocket watch with a painted enamel dial and case.

Vitreous enamel is essentially a glass product, so when it’s completed it is as hard and inert as glass. It will crack if it bends, but being protected inside a watch case, hairline cracks only occur after many years of temperature fluctuations bending the metal dial plate. This is sometimes called spiderwebbing, and it can actually make vintage enamel dials more desirable. That said, the same thing can happen on lacquer dials, so not all ‘spider dials’ are enamel. Because fired enamel is resistant to heat, chemicals, and impervious to water, you can also clean enamel dials extraordinarily easily. Dial cleaning is usually frowned upon because of how much damage it can do. A slip of a cotton bud can end up wiping away a printed numeral, or even revealing the brass plate beneath. If you put a painted dial in a modern ultrasonic cleaner, it would come out with nothing on it. Enamel, however, can handle an ultrasonic with ease, and removing decades (or centuries) of dust and grime can even make some of those hairline cracks invisible. It’s also far more resistant to UV light, and won’t yellow in the sun like white paint loves to do.

Porcelain’s history and suitability for watchmaking

Porcelain vase ming dynasty
A porcelain vase from the Ming Dynasty, Yongle Reign.

While the misnomer of porcelain has been applied to enamel clock dials for centuries now, there are actually some dials which are made from true porcelain. It originated in China, which is why Europeans started simply calling it fine china. Even the word porcelain has European origins, named after the Italian word for a type of sea snail shell called porcellana. In China, it’s called cí (瓷). Hard paste porcelain is what is considered ‘true’ porcelain, and it’s made from a mix of kaolin clay and other silicate minerals which help to lower the required firing temperature. There’s also a kind called soft paste porcelain which stemmed from Europeans trying to copy Chinese products at a lower cost, using the likes of soapstone, limestone, and a similar type of frit that forms the base of vitreous enamel.

atelier wen porcelain odyssey
The Atelier Wen Porcelain Odyssey.

Generally speaking, the process of manufacturing porcelain watch dials is too difficult, and the results are incredibly brittle. When an enamel dial can offer a similar if not identical look, why would anyone bother with something that’s usually reserved for decorative tableware? Well, watchmakers will pursue any avenue they think is interesting enough. That’s how we have ended up with several brands such as Seiko, Frederique Constant, Atelier Wen and Hermès who have experimented with true porcelain dials. The recipe has to be altered to increase the materials strength so cracks won’t appear from ordinary wear, vibrations and bumps.

Why do enamel and porcelain look so similar?

seiko presage spb449 porter classic dial
The Seiko Presage SPB449, which has an enamel dial.

You might be thinking that any black or white gloss dial is going to look identical, but not to the discerning eye. Even subconsciously, enamel and porcelain both share a trait which something like lacquer or paint can’t replicate. Their colour may appear opaque, but they have a degree of milky translucency. When light hits them, it scatters beneath the surface and diffuses, creating a softness and dreamlike quality across its surface. It’s similar to that of a marble statue. Lithophanes are a fascinating example of this quality from the 19th century, being thin sheets of porcelain that are carved with popular images and designed to be placed in front of a candle or lamp to show off its full spectrum of light and shadow. On something like a white enamel dial with black numerals, you can appreciate how the edges of those numerals may be clean and distinct, but never harsh. Truthfully, you will struggle to tell the difference between the two in a watch, however porcelain tends to have a little bit more of that diffused softness than enamel.