Capillary attraction is both a watchmaker's enemy and savior when it comes to lubrication.
Pivots are oiled to reduce friction and wear, and the Swiss lever escapement relies on grease to properly slide and deliver its power. Capillary attraction ensures that, if done properly, the oil will stay where it needs to be for years. Unfortunately for sloppy watchmakers, capillary attraction will also wick oil away from its target in a vanishingly short amount of time.
This is the escapement of a training watch that has been sitting idle for long enough for the oil to move. Grease is still present between the pallet jewel and the escape wheel tooth, but you can also see a bubble of lubricant that is slowly but surely creeping away from the impulse face and towards the rim, where it is useless.
There are several reasons that this could occur, but the most likely is sloppy/excessive oiling. Too much grease will glob up and start to flow away, eventually stopping the watch. A proper amount of grease will stay at the tip of the tooth, lubricating the escapement for years.
Watchmaking student at the Lititz Watch Technicum, formerly a radio and TV newswriter in Chicago.