Zaratsu polishing and hairline finishing:
Two skills that bring out the best in each other
The quality of the polishing is checked at each stage of the process and the craftspeople have a name for work that does not have to be re-done, which is ‘one-shot quality’. All the Zaratsu polishers in the Grand Seiko facilities share a determination to achieve this standard as often as possible because they have been committed to achieving ‘one-shot’ quality since their training days and they hate to fall short, even if only occasionally.
Another handcraft skill that is almost as difficult as Zaratsu polishing is the making of a flawless hairline pattern. There are many Grand Seiko creations with cases that have both polished and hairline finishes because the fine brushed surfaces express a soft serenity that contrasts with the brilliance of the mirrored surfaces. The mirrored surface is set off by the hairline finish, and the hairline surface is set off by the mirrored surface.
The hairline patterns are formed after the case has been polished to a mirror finish through Zaratsu polishing and the final buffing. So why is Zaratsu polishing necessary? According to Takahiro Ushiyama, the specialist in this process, “It’s because the hairlines will become irregular if there is even the slightest distortion on the surface.”
The creation of the hairline finish, which is the final process in the polishing of the case, is done by pressing and sliding the case against a metal plate covered with 400- to 800- grit sandpaper. If the amount of pressure applied and the speed at which the case surface is moved is changed, different kinds of hairlines will result. For flat surfaces, the case is pressed down on the sandpaper once and moved left and right, but for curved surfaces, a twist of the wrist is also required. Hairlines that are cut too deep cannot be corrected. At times, depending on the area, hairlines are made by attaching sandpaper to the tip of a rod and brushing it on the surface. Ushiyama, who is in charge of this difficult hairline finish, says, “Unlike some parts of the movement manufacture, our work is seen in close up by our customers in the display cases of our stores. This is gratifying but is also precisely why I cannot lose focus.”
The Grand Seiko Style was born to ensure that Grand Seiko timepieces are not just about movement accuracy, but are also brilliant and desirable objects to see and to hold. Zaratsu polishing has become a crucial part of achieving this result and is only possible thanks to the superlative skills of the craftsmen and women who practise this most difficult of arts.