VintageWatchstraps Logo

Vintage Watchstraps

Straps for Vintage Fixed Wire Lug Trench Watches or Officer's Wristwatches

Blog: Enamel Dials

Date: 31 October 2018

Copyright © David Boettcher 2005 - 2024 all rights reserved.

I make additions and corrections to this web site frequently, but because they are buried somewhere on one of the pages the changes are not very noticeable. I decided to create this blog section to highlight new material. Here below you will find part of one of the pages that I have recently either changed or added to significantly.

This section is from my page about Swiss marks that can be found at Dials and Hands.

If you have any questions or comments, please don't hesitate to contact me via my Contact Me page.

Enamel Dials

Porcelain Dials?

Sometimes enamel dials are incorrectly described as “porcelain”: this is wrong. Porcelain is made from clay and is not suitable for watch dials; it is used for tableware such as plates and bowls. Watch dials are made using vitreous enamel, a type of glass. In the USA this is called “porcelain enamel”. This is often shortened to just “porcelain”, which is inaccurate.

In the eighteenth century, the process of using vitreous enamel to make high quality dials with white, cream, or sometimes black, backgrounds, with hour numbers, minute tracks and other other details in vitreous ink, was developed. These superseded the metal dials that had been used previously.

The word “enamel” refers to any hard shiny coating such as tooth enamel, enamel paint, or even nail enamel (nail varnish). However, when used in the context of watch dials, enamel refers to an opaque or semi-transparent hard, glass like, surface applied to a metal dial plate by vitrification. Vitrification (from Latin vitreum (glass) via French vitrifier) is the transformation by melting of a substance into a glass. The full name of the substance used for watch dials is vitreous enamel.

Vitreous enamel dials have a very hard surface which is usually shiny and reflective like glass, but the surface can be made matt by rubbing with abrasive after firing.

Vitreous enamel is made from powdered glass. Tin oxide is added to make it opaque white, other chemicals are used for other colours. To make a dial the enamel is fused onto a copper dial plate by firing in an oven at high temperature, melting the glass and causing it to run together to produce a smooth glassy surface. First the overall white or black background is made, which might take four rounds of firing and smoothing to get the desired finish. Then the numbers and tracks are drawn on in black or white enamel ink, which is then also fired, at a lower temperature, to fix it to the white background.

After firing, vitreous enamel is invulnerable to ageing or fading and can be easily cleaned; an enamel dial will happily go through an ultrasonic clean. Vitreous enamel will be cracked if the dial is flexed, e.g. by being handled clumsily or levered off from the movement without releasing them first, but apart from this kind of physical damage they will last forever.

Enamel dials are expensive to make, so in the twentieth century cheaper materials were used, usually by printing the details onto a metal base and then covering with clear lacquer. Such dials are prone to discolouration, fading, and spotting, but are are extremely delicate and cannot be satisfactorily be cleaned.

To make an enamel dial, a sheet of copper is cut to the correct size and shape, with holes for the hand arbors, and "dial feet" attached to its underside. Dial feet are small copper rods attached to the underside of the dial, usually by welding or soldering. They enter holes in the movement bottom plate, where they and are gripped by screws or clips. Over tightening the dial feet screws is a frequent cause of distortion to the dial plate, causing the enamel to crack.

In manufacture, the copper dial plate is coated with crushed and finely powdered glass. It is then heated in a furnace to about 800°C until the powder melts and becomes liquid, bonding to the copper and fusing together to form a coating of glass with a smooth glassy surface. This process is usually repeated several times, with the dial being cleaned and rubbed down between each layer, to get a perfectly smooth and opaque surface.

The numerals and minute and seconds tracks are then added in vitreous painting enamel, sometimes called vitreous ink, either hand painted or transferred with a stamp, and the dial is fired again. This melts the enamel of the numbers and other details and bonds them into to the base layer of enamel. In the cross section I have shown a white enamel dial with red ink on it, say a red number 12. When the enamel of the numbers and other details melts and bonds with the underlying enamel it becomes virtually flat with the dial surface as the cross section shows. The numbers and tracks become as much a part of the dial as the underlying enamel and cannot be removed.

Initially the numbers and tracks were painted by hand, but later an engraved copper block was used. The engravings were filled with vitreous ink and a gelatine pad used to pick up the ink and stamp it onto the dial. In this way many dials could be made accurately and quickly.

Enamel Paint

Fake “Rolex Marconi” Logo: Click image to enlarge.
Dial cross section
Dial Cross Section (not to scale).

The drawing of an enamel dial cross section shows how enamel paint can be added to a vitreous enamel dial. Unlike the vitreous ink used to make the markings and numerals on the dial, the enamel paint cannot be fired - the paint would just burn. This means that the enamel paint does not form a strong bond with the underlying vitreous enamel, it just sits proud of its surface as shown in the drawing.

Enamel paint was often used to add a British retailer's name to an enamel dials of watches that were imported into Britain before the mid 1920s. Before the mid 1920s British retailers would not buy watches with a manufacturer's names or brand on their dials. If there was any name on the dial, it was that of the retailer. A small number of retailers were large and important enough to have their names or brands put onto dials in fired vitreous ink as they were made, but most did not, so enamel paint was used.

This means that Rolex, Longines, Omega, etc. watches sold in Britain before the mid 1920s didn't have their brand on the dial, and sometimes there was no name to be found anywhere. Nowadays most people expect to see a name on the dial, so some unscrupulous people have names painted on to make the watch more saleable (read "valuable"). It looks wrong.

Rolex is the most faked watch brand, so this addition of a name onto a dial in enamel paint happens most often with the Rolex name. Needless to say, just painting Rolex onto a dial does not really transform a watch into a Rolex watch. Sometimes the name is added to a genuine Rolex watch because the owner expects to see it there, but often watches that were never Rolex watches in the first place receive a new name. This is what has happened with the dial of a Marconi watch shown in the image here. If you enlarge it you can see the shiny new enamel paint on the surface of the vitreous enamel dial. It is obvious that this had been painted on quite recently.

Enamel paint is a totally different material from vitreous enamel, it is called enamel because it forms a harder, glossier, surface than other paints such as oil paint. However, enamel paint is nothing like as durable as the vitreous enamel of the dial itself. Unlike vitreous enamel, enamel paint can be easily dissolved by a solvent such as acetone or isopropyl alcohol.

Unlike the fired vitreous ink of the numerals and tracks, enamel paint doesn't bond into the underlying vitreous enamel but remains on its surface. It can usually be easily distinguished from the fired numbers and tracks by looking obliquely across the dial with a lens when it can be seen standing proud of the surface as illustrated. Because the vitreous enamel of the dial is very shiny, enamel paint has difficulty sticking to it and the added names have often become badly worn, or disappeared altogether.

If you look carefully at a vitreous enamel dial and detect that a name has been added in enamel paint, but the name doesn't show any signs of ageing, chipping or flaking, then it is quite likely that the name has been added recently.

If you have any comments or questions, please don't hesitate to get in touch via my Contact Me page.

Back to the top of the page.

Copyright © David Boettcher 2005 - 2024 all rights reserved. This page updated May 2023. W3CMVS. Back to the top of the page.