4 ms·
Japanese jam jar lids close on their own, as if by magic
- h2odragon 5y agoA guess: The jam sucks water out of the air, lowering its volume, producing vacuum, which is sufficient power to run the lid down the threads. There would likely be a correlation between level of jam in the jar and speed of closing / ability to do it at all; a larger volume of air will take longer to shrink and have more elasticity so it might only work for almost full jars.
- zaik 5y agoI don't think jam can suck water out of the air constantly at this speed. Does it work with an empty jar?
- moistly 5y agoWhat kind of weird watery jam do you have? The air suck must be enormous, to spin a lid down quickly. Are you sure your not spreading desiccant on your toast?
- morei 5y agoFor those that don't know: Concentrated sugar solutions are indeed hydroscopic. So it will indeed absorb water out of the atmosphere. It's still doubtful that it will do it fast enough to create any significant pressure differential though :)
- Epiphany21 5y agoEven if this was the case I doubt it would create a strong enough vacuum to move the lid. I think the threads just slope downwards a little more than other jars and they let gravity do the rest. Maybe the lid is lined with a slippery rubberized material that creates a seal, which would minimize friction allowing the lid to spin with minimal force. Edit: if someone has one of these jars, tilt it a little and then try lid trick. I bet it won't work.
- newaccount74 5y agoCould also be cold jam. When the lid is open, the air inside the jar would be room temperature. As soon as you put the lid on it, the air starts cooling down because the jam is cold, which would lower the pressure, and then the outside air would push the lid down, turning it. Or it's just gravity.
- h2odragon 5y agoI like that, cooling would be a much larger effect than desiccation.
- retrac 5y agoI suspect it's just gravity pulling the lid down along the groove. Kind of like going down a spiral slide. With metal on glass it probably has relatively low friction. I've seen nuts thread themselves down bolts as long as a foot, with just the slightest initial push, in a similar manner.
- hackernewds 5y agoExactly. Need to emphasize that, while gravitational force is strong enough to send the lid down a well grooved jar, it still needs to be tightened
- eternityforest 5y agoIt's amazing to see but I think it's just like a ball rolling down an inclined plane. A screw is just a twisted inclined plane. For various combinations of friction and angle gravity can make it happen.
- netizen-936824 5y agoThis is exactly it. I'm not sure why people are surprised by this, I've seen it happen plenty of times before. The lid never tightens itself, it literally is just falling into place along the grooves. Why is such boring, normal stuff going 'viral'?
- 0des 5y agoBecause tiktok and short form easy to consume media is catchy.