In uk.d-i-y, Man at B&Q wrote:
On Dec 12, 12:56*pm, Mike Barnes wrote:
In uk.d-i-y, D.M. Procida wrote:

M wrote:

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.

i would prefer araldite, can I ask why?

I want to use it to demonstrate a point about physiology and to show how
- when making strenuous efforts against resistant physical objects - we
typically contort our bodies in inefficient ways.

You sound like the right sort of person to confirm or deny a pet theory
of mine that's usually greeted with some scepticism. I believe that, all
other things being equal, a left hander will find it easier to unscrew a
difficult lid than a right hander. The body's geometry makes the right
hand stronger turning clockwise[1], and the left hand stronger turning
anticlockwise. Combine that with the left-hander having a stronger left
hand due to greater use, and the result is clear.

Even if this theory isn't true, explaining it lessens the embarrassment
when people see how easy it is for me (left handed, of course) to open
the jar they've been struggling with.

[1] which is why the "right hand thread" became the norm, people
attaching more importance to tightening than loosening

But with a jam jar you can just as easily open it by twisting the jar
clockwise with the right hand, rather than twisting the lid anti-
clockwise. Like the Aikido thing, it's all about technique.

Whatever you do one hand is clockwise and the other anticlockwise.
AFAICS the important hand is the one on the lid, which is relatively
small and awkward to grip. Which is why, for a right hander, the best
thing to do is to turn the jar upside down. And stop as soon as you
sense the slightest movement!

--
Mike Barnes