The sealing of a fully automatic mechanical watch's case is a crucial barrier to ensure the long-term, stable operation of its movement. Dust intrusion or oxidative corrosion from its components in a fully automatic mechanical watch, a crucial component for power output and timekeeping, can directly impair timekeeping accuracy and significantly shorten its lifespan. Reliable case sealing mitigates these two risks at the source.
From a dust-proofing perspective, the movement of a fully automatic mechanical watch is filled with precision components such as gears, hairsprings, and escapements. These components fit together with extremely tight clearances and often rely on specialized lubricants for smooth transmission. If a fully automatic mechanical watch's case is not adequately sealed, dust particles in the air can slowly seep into the movement through gaps in the case (such as where the crystal meets the case and between the crown and case). These seemingly minute particles of dust first adhere to the gear teeth, increasing transmission friction and causing the smooth operation normally maintained by lubricating oil to become sluggish, causing the fully automatic mechanical watch to run too fast or too slow. If dust particles become lodged in the hairspring, they disrupt its uniform vibration, further deteriorating the watch's accuracy. More seriously, dust particles mix with the lubricating oil within the movement, forming an abrasive "sludge." This sludge acts like sandpaper, wearing away at gears, shafts, and other components. Over time, this can damage the precise dimensions of these components and even cause the fully automatic mechanical movement to stall. A well-sealed watch case effectively prevents dust from entering, maintaining a clean operating environment for the fully automatic mechanical watch movement.
To mitigate oxidation, most components in a fully automatic mechanical watch movement are made of metals such as steel, copper, and alloys. These materials are highly susceptible to oxidation and corrosion when exposed to oxygen, moisture, or corrosive substances. When a fully automatic mechanical watch's case is not properly sealed, oxygen from the air will continuously come into contact with the movement components, causing slow oxidation. This can lead to fine rust on steel parts and a patina on copper plates. These oxidation products not only diminish the smoothness of the components and increase resistance, but also allow oxidized debris to enter the movement, causing secondary damage. During daily wear of a fully automatic mechanical watch, salt from sweat, moisture from the environment, and even cosmetic residue can penetrate through cracks in the case and accelerate oxidation and corrosion of the components. Salt from sweat can cause rapid rusting of steel pins, while chemicals from cosmetics can destabilize lubricants, further accelerating component degradation. A reliable case seal blocks these substances, reducing the chance of oxygen, moisture, and corrosive elements reaching the movement components, thereby slowing oxidation and maintaining their original performance.
It's important to note that the sealing of a fully automatic mechanical watch case isn't dependent on a single structure. Instead, it's achieved through the coordinated efforts of multiple components, including the sealing rubber ring between the crystal and the case, the screw-down locking mechanism (or sealing rubber ring) of the crown, and the seal between the caseback and the case. Once these sealing structures age, deform, or become damaged, their sealing performance deteriorates. Even if the fully automatic mechanical watch's movement is performing well, dust intrusion and oxidation can accelerate malfunction. Therefore, regularly checking the condition of the seals (such as whether the seals are hardened and whether the crown is tightly locked) and promptly replacing any deteriorated components are crucial for maintaining the seal and protecting the movement.
The sealing of a fully automatic mechanical watch case prevents dust from damaging the movement's transmission and lubrication systems, slowing the aging of metal components and providing a stable and clean operating environment for the movement. This is crucial for ensuring the accuracy and longevity of a fully automatic mechanical watch.
