V · Water resistance and maintenance

The “100 m” on the caseback tells part of the story. The rest is in the seals, crown, crystal and everything that happened since the last test. For a pre-owned watch, what matters is what the watch can withstand today and what you plan to do with it tomorrow.

Read the water-resistance rating in context

The marking relates to test conditions and should be read alongside the instructions for the reference. The number in metres alone does not describe every permitted use. A screw-down crown helps close the case, but it is one part of the system. Ageing seals, an impact or a previous opening can change how the watch performs in practice.

If you want to swim with a used watch, first check that the model is intended for that activity and ask a watchmaker for a test appropriate to the piece. A dated result with the test pressure stated gives you evidence about its condition at that moment. “It has never let water in” tells you what the seller observed, without establishing how the watch would perform the next time it got wet.

Match the care to the situation

For routine cleaning, start with a soft, dry cloth. Avoid solvents and abrasives. Keep a watch out of water if its resistance is unknown. With a suitable, tested watch, follow the manufacturer’s directions after exposure to salt water. Seiko’s guidance for its water-resistant watches includes rinsing in fresh water with the crown closed and drying with a soft cloth.

Avoid operating the crown when the watch is wet, and check the manual before using pushers. A hot shower or sauna is a different environment from a brief encounter with rain. If condensation persists inside the crystal, take the watch off and bring it to a watchmaker promptly. Heating the case at home can delay the work it needs.

Separate regulation, overhaul and refinishing

Regulation aims to correct the rate. A movement overhaul may include disassembly, cleaning, inspection, lubrication and adjustment, with parts replaced as required. Work on the case or bracelet is a separate job. Ask for an estimate stating what is included, whether parts will be replaced, and whether refinishing or a pressure test is part of the service.

Service intervals depend on the maker, watch and use. A sudden rate change, consistently reduced reserve, a rough crown or an irregular calendar warrants attention. Before authorising refinishing, decide whether you prefer to keep the surfaces and edges as they are. Removing material changes the case and cannot be reversed.

Start a service history today

Keep the invoice, date, parts replaced and results of any tests. A simple record makes the next service decision easier and helps a future buyer understand what was done. The Maison’s Watch Passport records that context and distinguishes documented history from gaps in the record.

What a water-resistance test should record

Ask the workshop to note the reference, date, test pressure and result. A dry test can measure how the case responds to a change in pressure, depending on the equipment and protocol. If the watch fails, the workshop should look for the cause before replacing components. It may be an aged seal, damaged crown or distorted mating surface. Ask whether a final test is included and what use is recommended after the work.

Revisit the assessment if the watch takes a knock, is opened for a battery change or will be used differently. For a vintage watch, discuss whether it is sensible to keep it dry even after work has been done. Preserving a period case, crown or crystal may matter more than making the watch suitable for swimming.

Maintenance outside the movement

Check the parts that keep the watch on your wrist. On leather, look for cracks around holes and layers beginning to separate. On a metal bracelet, check for a protruding pin or screw, unusual play and secure clasp engagement. A compromised bracelet needs attention before the next wear even if the movement is running well.

For a battery quartz watch, a battery change is an opportunity to inspect the caseback gasket and arrange a suitable test. For a solar or other rechargeable movement, first confirm the charging procedure and specified component in the manual. Give the workshop a short list of symptoms and explain how you intend to wear the watch. That helps distinguish work that is urgent from work that can wait.

The next chapter brings these decisions together in a plan for a collection that fits your wrist, budget and everyday life.

For the manufacturers’ directions, see Seiko’s water-resistance and care guides and Hamilton’s mechanical watch instructions.