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Tuesday 30th August 2016
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How Do They Do The Safety Buttons In Jars?


When you buy a jar of sauce, it has a safety button on the top showing if a jar's been opened. How do they make the jar with the button in the down position?
Daniel, Barnet



** Definitive **
Name: Bob, Youll
Qualification: Jam-making genius
Answer: The contents go in the jar when they are hot, you then put the lid on and when it cools down, it causes a semi-vacuum which sucks down the safety button on the jar.

** Additional definitive **
Name: Anwar, Croydon
Qualification: Jarhead
Answer: This is an amendment to Bob's answer. For olives and pickles in these jars, the lid is put on at such a high velocity, it essentially sucks the air out of the jar and sterilises the contents of the jar.

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