Hand bluing

The design of my minute and hour hands is inspired by my background in horological restoration work; however, my goal was not simply to make a copy of an existing hand, but rather to capture the elegance of traditional hands and combine their aesthetic with contemporary legibility. For this reason, from the very first sketches, I also wanted my hand design to have an integrated possibility of using Super LumiNova in the most legible manner possible. This is combined with a traditional hand bluing technique.

Blued hands and screws are certainly attractive details that catch the eye of watch collectors; however, the function of bluing specific parts of a watch was traditionally protective, in order to seal the metal surface of the hands from the influences of possible corrosion over the long term. Commercial watch manufactures normally utilize a chemical coating to achieve this, whereas traditionally it was done by hand on a one-by-one basis, using heat followed by a cooling down of the part in air, or drenched in water or oil according to the taste of the watchmaker.

My process of hand bluing starts by heating the particular hand in a layer of special sand over the flame of a small alcohol lamp, then removing it from the sand when the correct temperature (and color) has been reached; thereafter it is then allowed to slowly cool down at room temperature. For smaller parts like screws, a small metal holder is used following a similar heating process. 

Since it is impossible to heat the thicker parts of the hand the same amount as the thinner parts, the result is that hands blued this way are instantly recognizable by the chromatic passage from any shade of dark blue to the spectrum of dark purple and everything in between, following a pattern concurrent with the taper, rounding and form of the hand. Furthermore, this very delicate change of color will be different in each identically manufactured hand, even when they are of the same shape. 

If the taper of the one hand is a miniscule fraction of a millimeter different from the next, it will also spread the heat slightly differently within the hand, thus the chromatic color changes will be in slightly dissimilar places. 

In large production facilities of course, there is no time for work executed like this, and with multiple thousands of watches in production, the assembly line also demands a uniform and clear definition of ‘blue’ which is not workable with the subtle, organic color changes of traditional methods.

The result is that the majority of blued hands destined for the mass production market are given a chemical bluing treatment, therefore dipped in a color bath that results in a uniform color with no chromatic changes. On a purely technical note, chemical bluing will leave an exterior layer that does not bond closely to the metal; with hand bluing it is the metal itself that takes on the bluish color, so there is no coating liable to flake or fall off.

Before (left) and after (right) the hand blueing process

More details in the Video

Movement finishing