Opening this jar is made easier by cooling or heating?

[robertphy]

I've found this question online and don't agree with the explanation given.

There’s a tight lid on a jar that you need to get loose.
The lid on this jar is made of wood and is supposed to unscrew from the jar — if only it wasn't stuck. The coefficient of thermal expansion of the glass jar is higher than that of the wood lid.
How can you make the lid easier to remove?

Explanation

If you heat the lid and the jar, then the jar will expand more than the lid does — which would make the lid of the jar even tighter and more difficult to open.

If you cool the lid and the jar, then the jar will contract more than the lid does, leaving the lid relatively large compared to the jar and easier to remove.

I disagree. If you heat the jar, the diameter of the top opening increases more than the diameter of the wooden lid, making it looser. The opposite happen if you cool the jar and the lid.
Can you please clarify what's happening, in your opinion?
Thank you

 

[PeroK]

I disagree. If you heat the jar, the diameter of the top opening increases more than the diameter of the wooden lid, making it looser. The opposite happen if you cool the jar and the lid.

Why would the wood expand more than the glass if its CTE is less than that of glass?

Can you please clarify what's happening, in your opinion?
Thank you

The CTE of the glass is greater than that of glass, so it should expand more on heating and contract more on cooling.

 

[Lnewqban]

Which one has the female contact surface or thread?
That one has to expand, or the other one has to contract.

 

[256bits]

Which one has the female contact surface or thread?
That one has to expand, or the other one has to contract.

Looks like the devil's in the details.
A cork in a bottle is similar in line to the OP reasoning.

 

[robertphy]

Why would the wood expand more than the glass if its CTE is less than that of glass?

The CTE of the glass is greater than that of glass, so it should expand more on heating and contract more on cooling.

Thank you, now I understand the point.

 

[swampwiz]

Just thought I'd mention a product that eliminates the need for heating a stuck jar. Just dry out the top & bottom surfaces and put one of these at each. It also works on a hard-to-open doorknob or spark plug.

https://www.amazon.com/dp/B07L59RQ6G/?tag=pfamazon01-20

 

[renormalize]

Surprisingly, they're limited to opening only American jars:

 

[swampwiz]

Surprisingly, they're limited to opening only American jars:
View attachment 327385

My high school English teacher would say that this a dangling modifier.

 

[jbriggs444]

Interestingly, real wood has a different coefficient of thermal expansion with the grain than across the grain. This suggests that the lid shape is not preserved. So the real world experience could be that both heating and cooling make the lid more difficult to remove.