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The myth of eternal sealing
A watch is never “waterproof forever”. It is until proven otherwise — and the proof, alas, often comes at the wrong time: at the edge of a swimming pool, in a downpour, in a bathroom saturated with steam. Watchmaking may have been in dialogue with the ocean since the first divers in the 1950s, but water remains the intimate enemy of movements. The good news? Without a testing instrument, you can already get very reliable clues about the water resistance of your watch, without putting it at risk. The idea is not to immerse it in a bowl, but to observe, to feel, to play with the temperature differences – like an old workshop master would do before turning on his pressure machine.
What “Water Resistant” Really Means
First of all, a useful reminder. The term “Water Resistant” refers to a standard (ISO 22810 for most watches, ISO 6425 for divers) and to a static test. In real life, pressure varies, heat expands joints, soap breaks surface tension and gets everywhere. Pragmatic translation:
- 30 m (3 ATM): splashes, hand washing. No shower, no swimming pool.
- 50 m (5 ATM): rain, hand washing, light sports use. Avoid swimming.
- 100 m (10 ATM): swimming and surface OK if crown handled correctly.
- 200 m (20 ATM) and above / ISO 6425: swimming, snorkeling, recreational diving according to specification.
And above all: waterproofness is never acquired. The joints age, impacts micro-crack a glass, a poorly screwed crown is enough to compromise everything.
Naked eye checks: warning signs
Crown and pushers
This is the first line of defense. Check the condition of the crown: scratchy screwing, unusual side play, an oxidized crown tube are bad signs. On a screw-down crown, the sensation of “stop” should be clear, the rotation silky. The non-locking pushers (chronographs) are vulnerable: check that they return properly and that no humidity or dirt remains around them.
Background, bezel, glass
Turn the watch under harsh light. Look for micro-nicks on the edge of the glass, signs of opening on the back, corrosion marks around the clipped or screwed back. On a diver, inspect the bezel insert and the pearl at 12 o’clock: a deforming impact can create a leak. Finally, any residual mist behind the glass after a rapid change in temperature is a red flag.
Three tests without equipment, at home and without risk
1) The controlled fogging test
Simple, non-invasive and enlightening. This involves exploiting external condensation to monitor for the possible presence of internal humidity.
- Clean the exterior glass to avoid confusion with a greasy film.
- Blow gently on the glass to create a light veil of mist on the surface.
- Observe the dissipation: it should be uniform and disappear within 2 to 3 seconds.
- If areas remain opalescent under the surface, or if fog seems to be coming from the inside, stop: your watch has probably gotten damp. Watchmaking direction.
Limitations: this test does not “certify” anything. Above all, it detects infiltration that has already occurred or a very worn joint.
2) The reverse thermal test (cold spoon)
A workshop classic…with the means at hand. You create a gentle thermal gradient to reveal the presence of internal water.
- Let the watch cool for 10 minutes near a lamp or against your wrist (no hot radiator).
- Place a metal spoon cooled in the refrigerator for 5 minutes on the glass for 3 to 5 seconds.
- Observe immediately: if a ring of condensation appears under the glass, even fleeting, humidity has entered. The clearer the halo, the more urgent the intervention.
Pro tip: Do this test in the morning, when the watch is slightly cooler than the surrounding air. The reading is more contrasted.
3) The “feeling” of the crown
This is not a laboratory test, but experience shows it: a shaped joint is betrayed by feeling.
- Unscrew/screw the crown slowly. Look for the soft strength of the O-ring. Too dry? Metallic squeaks? Feeling sandy? The joint has probably hardened.
- Pull the crown to the time setting position: pronounced lateral play or soft return indicate wear of the tube or stem, critical areas for water resistance.
At this point, it is better to schedule a waterproofing overhaul: feelings don’t lie for long.
What you absolutely should not do
- No bowl of water, no “5 minutes under the tap”: an invisible micro-crack can turn the test into a disaster.
- No shower or sauna with the watch: heat, soap and steam expand the joints and break the surface tension.
- Never handle crown or pushers in water, even with a diver.
- Avoid sudden thermal shock (icy water after sun). It is the enemy of aging joints.
Maintenance: good reflexes for enthusiasts
Watchmaking culture is also the discipline of rituals. After the summer season or before a seaside trip, have the water resistance checked by the watchmaker: a pressure test costs little compared to a pitted dial or an oxidized movement. Replace the seals (crown, pushers, bottom) every 2 to 3 years under normal use, every year if you swim often. After a swim in the sea, rinse the watch in fresh water (if it is given at least 100 m and the crown is tightly screwed in). And remember: the “Water Resistant” label does not cover wear and tear over time.
When to consult without delay
- Persistent internal fogging or halo under the glass after the above tests.
- Visible oxidation on hands, indexes or flange.
- Abnormally low power reserve or erratic behavior after exposure to humidity.
- Crown difficult to screw in, sticky pushers.
In these cases, the longer you wait, the higher the bill. Immediate cleaning/drying, changing gaskets, and pressure checking often save the day — and the history your watch carries on your wrist.
In summary
Testing the water resistance of a watch without specialized equipment means knowing how to read the signs and respecting the mechanics. The fogging test, the thermal gradient of the cold spoon and the feeling of the crown offer relevant clues, without unnecessary risks. For the rest, an annual appointment with the watchmaker remains the best insurance – the only one, in truth – so that your memories never taste like salt water.
