*******Zaratsu Polishing Skill*******

 

Zaratsu polishing is a technique of finishing watch cases to create a mirror-like surface with sharp edges and no distortion. It is also known as blade polishing or tin polishing. It is performed by hand on one case at a time by skilled workers using the side of the polishing wheel, rather than the front. It requires the polisher to apply the right amount of pressure for the right amount of time at the right spot on the wheel, all of which is judged visually and tactilely.

Zaratsu polishing was introduced into Seiko by watch designer Taro Tanaka, who came up with the “Grammar of Design” that aimed to make Seiko watches more brilliant and precise. The name Zaratsu comes from the phonetic pronunciation of Sallaz, a German manufacturer of polishing machines that Seiko acquired in the 1950s.

Zaratsu polishing is often combined with hairline finishing, which is another handcraft skill that creates a fine brushed surface on the case. The hairline finish contrasts with the mirror finish and enhances the beauty of both. The hairline finish is done by pressing and sliding the case against a metal plate covered with sandpaper of different grits.

Zaratsu polishing is a very time-consuming and difficult technique that is only found in the best watches, such as Grand Seiko, Credor Eichi, Philippe Dufour or Kari Voutilainen.

*******Black Polishing Skill*******

Black polishing, also known as spéculaire finishing or mirror polishing, is a technique of finishing steel parts in a watch movement to create a mirror-like surface that appears black from certain angles, hence the name. It is used for steel screws, levers, bridges and other components. True black polishing is done by hand and only found in the best timepieces.

Black polishing is accomplished by rubbing the steel part against a flat surface covered with abrasive paste or powder, such as diamond or chromium oxide. The part is held by hand or by a tool and moved in different directions until all scratches are eliminated and a smooth surface is achieved. The final polish is done with a very fine abrasive and a gentle pressure.

Black polishing is similar to Zaratsu polishing in terms of creating a mirror-like surface, but it differs in the scale and the angle of reflection. Black polishing is done on smaller parts that are usually hidden inside the movement, while Zaratsu polishing is done on larger parts that are visible on the case. Black polishing reflects light only from one angle, while Zaratsu polishing reflects light from multiple angles.

 

*******Comparison Table*******