Cleaning

Cleaning a movement removes old, oxidised oil, dust, metal particles from wear, and residues from prior repairs, all of which accelerate further wear if left in place during reassembly. Professional cleaning is normally done with a dedicated watch-cleaning machine that cycles parts through a sequence of solutions — typically a cleaning bath, one or more rinse baths, and a final rinse — often combined with ultrasonic agitation to dislodge particles from recesses that cannot be reached by hand.

Not every part goes through the same process. The balance-and-hairspring assembly is usually cleaned separately and far more gently than the rest of the train, because ultrasonic energy can distort a delicate hairspring or loosen a balance's timing screws; many watchmakers clean the balance largely by hand, with a soft brush and minimal immersion time. Shock-absorber assemblies, some jewels, and any part with an existing finish that solvents could damage also need individualised judgement rather than a single default cycle.

Cleaning solutions themselves are chosen for compatibility with the materials present: strong solvents that are fine on steel and brass can damage gilding, certain plastics, painted or lacquered dials, or shellac used to hold pallet stones or hairspring studs in some movements, so a dial is never run through a movement-cleaning cycle, and older movements with shellac-set components require solutions and dwell times chosen with that in mind.

After cleaning, every part is dried thoroughly before reassembly, since trapped moisture leads directly to rust on steel components — one of the most damaging and hardest-to-reverse faults a movement can develop, particularly on fine pivots and hardened steel parts like the pallet fork and escape wheel pivots. Watchmakers typically inspect parts under magnification after cleaning, both to confirm the cleaning worked and to catch wear or damage (a chipped pivot, a cracked jewel) that the disassembly stage may not have revealed.

The reason this lesson exists in a curriculum rather than a manual is the same reason repeated throughout the Intermediate track: understanding why professional cleaning is a controlled, multi-stage process — and why household solvents, ultrasonic jewellery cleaners, or improvised methods are a common cause of ruined vintage movements — is what lets an owner make an informed choice about servicing, even if they never clean a movement themselves.