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Blued hands in watchmaking

Watchplayers commonly are interested by some factors such as luxury brands, sophisticated movement, fascinating decoration, rare materials, eye-catching design or just a…blue hand. Ranging from luxurious to average watches, a blue hand is always being the noticeable and irresistible beauty. That I am talking about is the perfect and consistent blue hand producing by heating white steel rather than the blue little thing produced in a clumsy way with the pale color by normal painting and plating technology.

If you still cannot imagine how that process takes place, let’s take a look at these images.

Blue hands of a Chronoswiss. Source: Novatime

Blue hands of a Chronoswiss. Source: Novatime

A closer look at blue hands in a Chronoswiss. Source: Novatime

A closer look at blue hands in a Chronoswiss. Source: Novatime

The blue color of the hand

As we see in the different angles, blue hands appear in different type of blue color. The below image shows that when it comes to the same watch, looking at either directly or under light going perpendicularly, only black color of the hand can be seen.

At the improper angle, the blue color of hands cannot be seen. Source: Novatime Lab

At the improper angle, the blue color of hands cannot be seen. Source: Novatime Lab

To obtain the further understanding on this color changing, we need to understand the mechanism of making blue hands. The blue hands, at first were the white steel (stainless steel) which then were quenched to reach the desired toughness. Steel was heated to the high degree of over 700-900 °C and quenched in solutions such as water or oil later on. Commonly, in metallurgy, to avoid the brittleness because of overhardening steel, it is common to temper by heating the quenched steel up to 200-500 °C  then allowing it cool in order to alter the structure of the materials as well as reduce mechanical stress. There is an interesting point here, that is when tempered in different temperature, the surface of steel creates multiple colors which forms a color band changing over time.

Multiple tempering colors of steel. Source: Zaereth/Wikipedia.

Multiple tempering colors of steel. Source: Zaereth/Wikipedia.

There would be a simple explanation for the blue hands: when reaching the tempering temperatures, the oxidation on the surface forms the oxide layers with varied thickness. These layers were super thin, not completely transparent and just partially allowing light going through. Therefore, as light strikes the surface of a film, it is either transmitted or reflected at the upper surface. The phenomenon in which two lights interfere called thin-film interference.

It depends on the thickness of oxide layers and the angle of lights that explains the multiple colors seen. Theoretically, the popular blue that is usually seen in watches was created by tempering at roughly 300 C.

Thin film interference (purple). Source: Wikimedia Commons.

Thin film interference (purple). Source: Wikimedia Commons.

Blue hands machining in watchmaking

The techniques of tempering steel and coloring on the surface were discovered a long time ago and applied right the first stage of watchmaking industry. Although the official record of the first blue hand has not been founded yet, to the best of my knowledge, since 1783, Breguet introduced the hand resembling a hollow apple or crescent moon named after him, made of gold or blued steel. The introduction of that technology contributes to the theory of the long appearance of blue hands .

Breguet hands made from blue steel fro pocket watches. Source: Breguet.

Breguet hands made from blue steel fro pocket watches. Source: Breguet.

In fact, to manufacture a blue hand, it is common to follow these steps:
• Harderning the hands
• Cleaning bavia
• Tempering 1st (softening)
• Polishing
• Bluing
That basic process can be added or omitted one or two steps depending on the scale of manufacture or the requirements. In term of high-end hands, the requirements with high sophistication and similarity, the procedure from quenching, polishing to bluing manually all need to be ensured thanks to the massive support of machine controlling the temperature. Some tricks and knacks some time will be used to get the special blued color, which are the secrets of watchmakers.

The amateur watch-players also pay a lot of interest on the blue hands in wristwatches, pocket watches and clocks. Hence, there are number of videos and articles which provide in details how to turn the hands into blue color by using simple equipment. Obviously, the quality and sophistication never can be compared with that of professional manufacture. A video from Clickspring explains the principle of making blue hands by thin-film interference.

Screenshot from video of blue hands machining [8]. Source: Clickspring/Youtube.

Screenshot from video of blue hands machining [8]. Source: Clickspring/Youtube.

Blue hands in common watches

in these days, blues hands are supposed to be the tendency differentiating the watches and the design of watch’s surface. As for some brands, the perfect blue hands is the secrets of their technology which proves the high rank of their brands.

The blue hands, however, become out of reach for low and average users. The number of watches only priced from $200-500 can own good blue hands. Blue hands in varied prices are exemplified below.

Tisell priced about $250. Source: Novatime Lab.

Tisell priced about $250. Source: Novatime Lab.

Mido priced about $1500. Source: Novatime Lab.

Mido priced about $1500. Source: Novatime Lab.

Chronoswiss priced about $5000 - $10000. Source: Novatime Lab.

Chronoswiss priced about $5000 – $10000. Source: Novatime Lab.

Cartier priced about $5000-$10 000. Source: Novatime Lab.

Cartier priced about $5000-$10 000. Source: Novatime Lab.

IWC priced about $5000-$10 000. Source: Novatime Lab.

IWC priced about $5000-$10 000. Source: Novatime Lab.

Conclusion

Blue hands, at the moment, is the salient feature of design, the memorable remark of manufacturing capability, the irresistible factor that fascinates watch enthusiasts and the interesting and challenging thing to DIY. The principal and technology making an average blue hands has been cleared, so a lot of watched are equipped these special hands. Apparently, in the high-end and premium watches, the blue hands manually made become the highlights of the watches.
In addition to the aesthetic and technical features, blue hands are long-lasting thanks to the protection of oxide layers and the steel core. Over the hundred years, there are some blue hands which are still like new and telling the story of the simple but interesting part of a watch.

Nova @ Novatime Lab.

This article was written in Novatime Lab’s Technical Report (Watch Research). It can be updated in the future for better quality.

References

[1] Hands of Watches, Montre24 Watch Portal, URL: http://montre24.com/watchmagazine/62

[2] Quenching, Wikipedia, URL: https://en.wikipedia.org/wiki/Quenching

[3] Tempering (Metallurgy), Wikipedia, URL: https://en.wikipedia.org/wiki/Tempering_(metallurgy)

[4] Thin film interference, Wikipedia, URL: https://en.wikipedia.org/wiki/Thin-film_interference

[5] Breguet Hands, Breguet, URL: https://www.breguet.com/en/history/inventions/breguet-hands

[6] EXPLAINED: How To Blue Steel Screws The Traditional Way – With A Flame And Lots Of Patience, Watches by SJX, URL: http://watchesbysjx.com/2015/02/explained-how-to-blue-steel-screws-the-traditional-way-with-a-flame-and-lots-of-patience.html

[7] Bluing: The Process of Thermally Treating Screws, Worn & Wound, URL: http://wornandwound.com/bluing-process-thermally-treating-screws

[8] Spare Parts #12 Heat Bluing A Set Of Steel Clock Hands, Clickspring on Youtube, URL: https://www.youtube.com/watch?v=NhjiIPohUyw

[9] Blue Hands, BaCaitlin on Watchuseek, URL: http://forums.watchuseek.com/f2/blue-hands-403966.html

Author: Jennie Ng

A people person

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