GS Grand Seiko

Why Zaratsu polishing?

In the 1960’s, Seiko’s watches won several top awards in both the Japanese and Swiss observatory precision contests and these achievements put the company firmly on the world’s horological map. In terms of the exterior design of Grand Seiko, however, the company had not established any real identity for its watches and it was not until the appointment of a young design graduate to the task that any real focus was given to the visual identity of Grand Seiko. In 1962, this designer spent long hours at the WAKO store in Ginza, Tokyo’s most exclusive shopping district, watching how people reacted to watches from all around the world. He drew two conclusions. First, he saw that Grand Seiko watches did not have a clear and common identity; they were perfect as individual designs but not immediately recognizable in the WAKO showcase as Grand Seiko. Second, he realized that, in order to stand out and to attract the eye, Grand Seiko needed to have more brilliance. He saw that the way forward was to design watches with sharper angles and distortion-free surfaces so that they would “sparkle with quality”. The first two timepieces to demonstrate the aesthetics of the new style that he created were the 44GS, launched in 1967, and the 61GS released the following year. Acknowledged today as mechanical Grand Seiko masterpieces, they were, respectively, created at Daini Seikosha (now Seiko Instruments) and Suwa Seikosha (now Seiko Epson).

The key signature of the case design of 44 GS is the flat surfaces that are polished to a distortion-free, brilliant mirrored finish. The indexes and hands also have broad flat surfaces ensuring easy legibility even under the faintest light. Many prototypes were made before the Grand Seiko Style was finalized as it had to be both distinctive and flexible so that it did not limit the designers but acted as a compass showing the overall direction that each new design should take. As a result, the Grand Seiko Style has stood the test of time and even today, five decades after its creation, the Grand Seiko designers create new Grand Seiko timepieces using their own interpretation of the Grand Seiko Style according to their own methodologies and aesthetic sense.

Zaratsu polishing specialist Yuji Kuroki (left) and hairline finishing specialist Takahiro Ushiyama (right) of the Shinshu Watch Studio.

The Grand Seiko Style may have left the designers with more than enough creative freedom but it imposed a challenging requirement on the craftsmen and women who looked after the case production and polishing to develop new skills. One such was what came to be known as Zaratsu polishing. This was the solution that the team found to the problem of how to create perfectly flat, smooth surfaces with no distortion. This was a vital part of the Grand Seiko Style, which dictated that a sharp ridge be formed where two planes meet. To create a mirror finish by buffing was deemed insufficiently precise, as this technique inevitably softens the angle of the ridge. Zaratsu polishing was essential to the achievement of what the Grand Seiko Style demanded.

There are two ways in which Grand Seiko cases are made, NC (numerical control) machining and cold forging. The difference between the two methods is that one entails the carving of the case like a sculpture, and the other involves stamping it with several hundred tonnes of force. This was a process that lacked high precision in the past and that made deburring and other adjustments necessary but recent developments in technology have made it much more precise. Nevertheless, even now, the completion of the case requires the expert skills of the craftsmen and craftswomen in the processes that follow—sanding and rough buffing to smooth out any uneven surfaces followed by Zaratsu polishing.

In Zaratsu polishing the length of time the case surface is pressed against the rotating disc has to be changed depending on whether the center or edge of the disc is used, and this is also one of the reasons for its difficulty. The craftspeople have to learn to feel this difference as a sensation in their hands.

‘Zaratsu’ is the Japanese pronunciation of the name of a European company that used to make a polishing machine and is what the Grand Seiko polishers called the process that involves using that machine. The craftsperson holds and moves the surface to be polished in front, rather than at the side, of a rotating metal disc that has sandpaper attached to it. This way of polishing is much more difficult process but it makes the surface of the metal extraordinarily smooth. Following this process, a final buff is applied to burnish the surface to a mirror finish. This can be achieved even if the Zaratsu process is skipped, but distortion of the surface would be unavoidable. The quality of the Zaratsu finish is determined by a combination of various factors including how much pressure is applied to hold the surface against the rotating disc and for how long, and how quickly the surface is slid over the disc. And all of this depends on the craftsperson’s sense of touch.

Zaratsu polishing specialist Yuji Kuroki of the case workshop in the Shinshu Watch Studio says, “The difficulty of Zaratsu is achieving a perfect balance. Even if a section has been polished well, the left and right sides of the lug surface often end up slightly different. That is why it is not enough to just carefully polish the case, section by section. Rather, we have to increase the pressure used to hold the surface against the disc and finish the work quickly while observing the entire piece. I recall that it took months for me to gain the intuitive feeling needed for that.”