Hello, I will send it from Ginzo Public Relations because the watch studio is very busy. I hope you can take a look at it today as well ... Then, if you put a watch on the main subject ... It will turn black like this. Clock Studio The cause is Stain that has accumulated between the frames of the breath. Especially in the summer, you sweat a lot, so the accumulated dust absorbs the sweat and hardens. In that case, you cannot clean every corner with a brush or running water. Since it hasn't broken down, it doesn't need to be disassembled and cleaned, but there should be surprisingly many people who want to clean it anyway. Summer stains are persistent and can penetrate into the gaps in the breath and back cover. Such stains can be cleaned by disassembling the exterior once and applying it to an ultrasonic cleaner. For example ... If you try to ultrasonically clean a watch that is so Stain, it will look very beautiful like this. The vibration of ultrasonic waves generates micro bubbles in the water, and the shock wave generated at the moment when the bubbles burst crushes the Stain in the minute gaps. Mechanical watches are very delicate, so we recommend this ultrasonic cleaning. In addition to cleaning, it is good to perform regular maintenance.