Self-closing Japanese jam jar lids


Japan never ceases to amaze us – from hologram checkout registers to lickable television screens to self-closing jam jar lids, the country is full of wondrous creations.


Jam jar lid twists itself shut


self-closing jam jars - aohata jam jar close by itself
Video adapted from: @ktzwcrrk

On 10th March, Japanese twitter user @ktzwcrrk posted a video that showed the user placing the lid onto a jam jar, and the lid proceeds to twist itself shut. 

self-closing jam jars - aohata strawberry jam
Image credit: AOHATA

The jam jar in question is manufactured by Aohata, a jam-making corporation that is renowned for their delicious compotes.

self-closing jam jars - netizens reactions
Image adapted from: Twitter

Netizens were both confused, as well as amazed at this seemingly magical phenomenon, and were ultimately unable to figure out the science behind it.


Self-closing jar lids proven to work


Curious as to whether the videos of the Aohata jam jars were actually real or simply a sham, we decided to try it out ourselves.

self-closing jam jars - aohata jam jars visual
Video adapted from: Xiu Ting Wong

We only gently placed the lid on top of the jar, and it really did magically move by itself.


Our theory behind this seemingly magical phenomenon


After much contemplation, we have come up with a theory that could explain the science behind this phenomenon.

self-closing jam jars - fridge
Image credit: Brett Jordan

Most consumers would refrigerate the jam jars to prolong its shelf life. As a result, the air within the jar would be colder and thus exert less pressure onto the lid. The atmospheric pressure would then be greater than the pressure in the jar, hence when one places the lid onto the jar, the net force downwards would cause the lid to twist itself close.

self-closing jam jars - jar visual
Image credit: Rob Wicks

Of course, this would mean that this little trick could work with other jam jars, but having tried the same thing with several other jars and failing, we concluded that the design of the jar is pivotal to its success.

Perhaps Aohata designed their jars with this impressive function in mind, but as of now, we can’t know for sure as the company has not disclosed the truth behind this bizarre phenomenon.


Self-closing Japanese jam jar lids impress many


If Aohata really designed their jam jars with this function in mind, colour us impressed. Self-closing jam jars could pave the way for automated products to eventually dominate the market and serve our lazy selves to our utmost convenience.

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Cover image adapted from: @maisondechance_official and Rob Wicks

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