On Dec 12, 8:58*am, (D.M.
Procida) wrote:
I want to make an unopenable jam jar - one that will resist the
strongest grips.

What's the best way to achieve this?

I imagine that filling it up with boiling water, running a seam of
superglue along the rim and thread then screwing the lid on tightly
would get the best results.


Why the boiling water? Is that what you want it to be full of?

I recall doing something like this once - can't remember why. I used
Araldite and left the jar+lid in a recently-heated oven for faster/
stronger setting.

It 'mostly' worked. But the Araldite didn't properly fully adhere to
the glass and you could work the lid a little free. You might try
something similar with epoxy resins designed for glass.

Ah, I remember now - I was experimenting with making a cheapskate
'moneybox'!

HTH
J^n