A distortion-free explanation of what Zaratsu polishing actually is, and its not-so-Japanese origins

Zach Blass

In its pursuit to establish a point of difference of the brand, and its effort to educate watch enthusiasts beyond Japan of the high level of handcraft and quality of its watches, Grand Seiko succeeded in being well-known for its industry-leading technical skill in case finishing. Anyone who has ever looked into the Grand Seiko brand and into purchasing one for themselves has therefore come across the term Zaratsu. But what exactly is Zaratsu polishing? And where did it come from?

Zaratsu is not a centuries-old samurai sword finishing technique repurposed for watchmaking as some naively misconceive, and to be clear, it is not Grand Seiko spreading any sort of misinformation. They are very transparent about its true, phonetic origins. The word “zaratsu” is actually derived from the German word “sallaz”, which is phonetically pronounced “zarats” in Japanese. In the early 1950s, the polishing machines that Seiko acquired for their Hayashi Seiki facility were engraved with the name of the machine manufacturer “GEBR.SALLAZ”, or “Sallaz Bros“, and its phonetic pronunciation as “zarats” in Japan gave rise to the name of the polishing technique we know today – Zaratsu. The main difference between the “GEBR.SALLAZ” polishing machine and others is the use of the front of the rotating polishing disk rather than the side, allowing for greater uniformity in application.

This style of finishing is by no means exclusive to Grand Seiko. The same method of polishing has been used not only across Seiko Corporation brands such as Credor and higher-priced Seiko pieces but also by brands outside of the Seiko family, such as Citizen in its higher-end watches – suggesting a fondness for this method of polishing in Japanese watch firms.

In fact, watch companies around the world use similar techniques to achieve their highest standards of polishing, with many Swiss watch manufacturers using the term “black polishing” for a technique they typically use to finish parts of their movements. The key distinction between a brand like Grand Seiko and Swiss watch brands that black polish is the scale of the components such a high level of finishing is applied to. While Swiss or German watch brands will charge much higher for their watches with small black-polished components such as screw heads and bridges like Lange’s swan’s neck, Grand Seiko watches cost a fraction of the price despite the fact all of its cases have larger surfaces finished to this standard.

While Grand Seiko does not officially disclose such specifics of annual production, Zurich-based platform NZZ estimates that Grand Seiko manufactures between 50,000 – 60,000 watches per year (on par with brands like Patek Philippe). This means Grand Seiko has an unmatched velocity in achieving such a high level of finishing to a higher number and larger scale of components than any watchmaker in the world.

According to Grand Seiko, it takes a high level of discipline and patience to obtain the touch, intuition, and sensational cognizance required in order to master Zaratsu polishing. “The difficulty of Zaratsu is achieving a perfect balance,” Yuji Kuroki,  a Studio Shinshu Zaratsu polishing specialist, explains. “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.”

The ultimate goal of Zaratsu is not simply to introduce shiny mirror polished surfaces to a case, rather, it is the pursuit of creating flat, distortion-free, mirrored surfaces. Once Zaratsu polishing is applied to a case, the last step is to then apply the rich hairline brushing, an almost equally difficult task, to contrast the mirrored surfaces and create the “light and shadow” element mandated in Grand Seiko’s grammar of design. The distortion-free and flat surfaces Zaratsu polishing introduces are crucial to the final hairline brushing stage. Why? “The hairlines will become irregular if there is even the slightest distortion on the surface,” Zaratsu Polishing Specialist Takahiro Ushiyama explains.

So, how is Zaratsu polishing achieved and performed? Grand Seiko Corporation of America Brand Curator and National Training Manager Joseph Kirk once explained on the WatchUSeek forums: “In order to achieve this quality of finish for the final product, cases undergo a four-part polishing process. The polishing is executed by fixing the case or bezel on a chuck, and applying it to a rotating tin and/or abrasive wheel delicately. The wheel is cleaned and wet with a brush numerous times per case. It can take hours to finish just one surface. The tin wheels are made in-house, and the abrasive used is very fine (the details of which are undisclosed to the public). The result is, as mentioned, a distortion-free mirror finish, showing no blurring in reflections, only a pure and crisp image.”

The payoff is a geometric and faceted case with perfectly sharp lines that alternate between hairline brushing and distortion-free mirror polishing. If a more common buffing method was used instead, the edges of the facets would inevitably become much more rounded, and would result in something less distinct and eye-catching. I always love watching Swiss watchmakers or brand executives hold one of my Grand Seiko watches. The first thing many of them do is take their thumb or finger, move it carefully along the edges of the cases with an expression of marvel and disbelief in their eyes, knowing full well just how hard such case finishing is to achieve (and at a sizeable scale with consistency no less).