Any wristwatch has three major components, namely,
1. Watch case, which houses the mechanism,
2. The mechanism or module with dials & hands,
3. The strap to wear the watch on hand.
Watch case is a subassembly with glass, back cover and case pipe (to guide stem meant for time adjustment using crown). This subassembly is done at the in-house watch case plant that has five major shops–
1. Press shop
2. Machine shop
3. Polishing shop
4. Plating shop
5. Watch Case assembly.
In watchcase assembly, case center, back cover, case pipe, and glass are assembled together and later tested for joint-strength and water resistance (WR). The WR test is a mandatory statutory requirement for watches and is carried out by immersing the watch case in water for 10 minutes with the pressure of 5 Kg/cm2 or 7 Kg/cm2, based on specification.
Post testing, the cases are inspected for water entry with mild heating on the backside. Despite using demineralized water for WR test, we observe stain formation during the heating process. A lint-free cloth is soaked in ethyl-methyl ketone solvent (petroleum-based solvent) and then used for cleaning the stains. As this solvent has an unpleasant smell and has detrimental effects on human health, we want to eliminate the use of Ethyl Methyl Ketone from our process.