How to determine if a paint can lid is tightened?

I. Listen to the sound:
Clicking sound: A "clicking" sound, similar to a ratchet mechanism, usually indicates the lid is tightened and the seal is good.
Exhaust sound: A "whooshing" sound indicates the lid is not tightened and needs to be retightened.

II. Check the seal:
Smell: If you smell paint after tightening, the sealing ring may be worn out or the lid may not be properly closed; check it.
Paper test: Place a piece of paper on the lid. If the paper can be easily removed after tightening, the seal is not tight.

III. Simple tests:
Pressure test: Press the lid with your hand. If it is easily pressed down, it is not tightened; if there is no looseness when pressing, it is tightened.
Vacuum test: Create a vacuum inside the can and observe whether the pressure gauge is stable. If there is leakage, the seal is poor.

IV. Precautions

Sealing Ring Condition: If the sealing ring is aged or damaged, even if you hear a "click" sound, it may still leak air and needs to be replaced immediately.

Avoid Over-Tightening: Over-tightening may cause the cap to deform or the seal to fail. Tighten until you feel resistance.