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.

Daniele

"D.M. Procida" wrote in
message
...
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.

Daniele


Marmalade round the rim seems to work in our house.

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

jkn 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.


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

That's just to create a vacuum effect on the lid, to help keep it
closed.

Daniele

On Fri, 12 Dec 2008 08:58:11 +0000 someone who may be
(D.M. Procida) wrote
this:-

I want to make an unopenable jam jar - one that will resist the
strongest grips.

What's the best way to achieve this?

Do you want the contents, or the jar and the lid and the contents?

Has it already been opened?

If you only want the contents and a proper jar opener will not shift
it then drill a hole in the lid. If the jar has not been opened this
will release the vacuum. If necessary the hole can be enlarged to
remove the lid.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Fri, 12 Dec 2008 08:58:11 +0000,
(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? Someone can always smash it if they want to get it open.

--
(\__/) M.
(='.'=) Owing to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking most articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.
See http://improve-usenet.org

In article ,
David Hansen wrote:
If you only want the contents and a proper jar opener will not shift
it then drill a hole in the lid. If the jar has not been opened this
will release the vacuum. If necessary the hole can be enlarged to
remove the lid.

You've just done what I almost did. ;-)

--
*Why is the man who invests all your money called a broker?

Dave Plowman London SW
To e-mail, change noise into sound.

"M" wrote in message
...
Following up to D.M. Procida

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?

Sounds like a Christmas trick to play on a brother or similar -
"I bet I'm stronger than you",
struggle, struggle, struggle,
sleight of hand to swap to identical looking jar,
Pop!,

"That was easy"

In uk.d-i-y, 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.

I'd remove the soft sealing ring from inside the lid, the use a good
quantity of Araldite and cure it in the oven.

--
Mike Barnes

On Fri, 12 Dec 2008 11:02:55 +0000, David Hansen
wrote:

On Fri, 12 Dec 2008 08:58:11 +0000 someone who may be
(D.M. Procida) wrote
this:-

I want to make an unopenable jam jar - one that will resist the
strongest grips.

What's the best way to achieve this?

Do you want the contents, or the jar and the lid and the contents?

Has it already been opened?

If you only want the contents and a proper jar opener will not shift
it then drill a hole in the lid. If the jar has not been opened this
will release the vacuum. If necessary the hole can be enlarged to
remove the lid.

David .Read the OP again slowly...LOL

On Dec 12, 11:18*am, M wrote:
Following up to Dave Plowman (News)

If necessary the hole can be enlarged to
remove the lid.

You've just done what I almost did. ;-)

well, its the obvious conclusion to jump to!

No it isn't. The OP is perfectly clear. Hints of the DIY English
thread?

MBQ

D.M. Procida wrote:

I want to make an unopenable jam jar - one that will resist the
strongest grips.

No such thing exists. You could make one that's very difficult to open,
would that do?

On Fri, 12 Dec 2008 08:58:11 +0000,
(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.

I'd be inclined to try hot-melt adhesive.
If you use superglue or any other kind of hard setting glue there's a
chance that the bond could be broken - or that it might not fully take
to either the lid or the glass.
Hot-melt adhesive has some give in it, it's not as brittle as a hard
setting glue.
Best bet would be to try it, and use a jar opener for extra leverage
to test.

Regards,


--
Steve ( out in the sticks )
Email: Take time to reply: timefrom_usenet{at}gmx.net

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. It will spoil my
demonstration if the jar can be twisted open easily.

Daniele

OG wrote:
"M" wrote in message
...
Following up to D.M. Procida

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?

Sounds like a Christmas trick to play on a brother or similar -
"I bet I'm stronger than you",
struggle, struggle, struggle,
sleight of hand to swap to identical looking jar,
Pop!,

"That was easy"

Mate of mine (Mark, also a magician) used to do something similar with a
sharpie marker. He would remove the cap & apparently place it on the other
end of the pen. What actually happened was that he palmed the cap, and on
the other end of the pen was a duplicate cap super glued in place.

The unsuspecting punter would sign the playing card, then automatically try
to replace the cap - which he couldn't. After a little humorous patter Mark
would reverse the process and apparently re cap the pen. Very funny to
watch :-)


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

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

--
Mike Barnes

"D.M. Procida" wrote in
message
...
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. It will spoil my
demonstration if the jar can be twisted open easily.

Interesting, but is it true? I'd need some convincing that we would contort
into a less efficient position when trying to increase effort. I'd be more
inclined to concede that it might *look* like it's less efficient.

For any given task (eg. jam jar opening), how would you determing the
*optimum* method and decide what is less efficient?

Tim

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.

Daniele

I'm sure a suitable application of 'ki' would open it anyway

Alan
--
email =~ s/nospam/fudokai/

On Fri, 12 Dec 2008 13:39:06 +0000, ajp wrote:

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.

Daniele

I'm sure a suitable application of 'ki' would open it anyway

That, or a couple of slaps with a bokken.

Regards,


--
Steve ( out in the sticks )
Email: Take time to reply: timefrom_usenet{at}gmx.net

On Fri, 12 Dec 2008 11:02:55 UTC, David Hansen
wrote:

On Fri, 12 Dec 2008 08:58:11 +0000 someone who may be
(D.M. Procida) wrote
this:-

I want to make an unopenable jam jar - one that will resist the
strongest grips.

What's the best way to achieve this?

Do you want the contents, or the jar and the lid and the contents?

Has it already been opened?

If you only want the contents and a proper jar opener will not shift
it then drill a hole in the lid. If the jar has not been opened this
will release the vacuum. If necessary the hole can be enlarged to
remove the lid.

Read the question.

--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

"Mike Barnes" wrote in message
...
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],

Thinking about it and being right handed I must admit when faces with such a
jar
I always tend to try using my left hand as it just seems easier that way.
An old plastic container of PVA glue was the last time (not a jar)
and I grabbed a pair of pliers in the end to get it undone.


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

--
Mike Barnes

Tim Downie wrote:

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. It will spoil my
demonstration if the jar can be twisted open easily.

Interesting, but is it true? I'd need some convincing that we would contort
into a less efficient position when trying to increase effort. I'd be more
inclined to concede that it might *look* like it's less efficient.

Most people trying to twist open a tight container will hold it towards
their dominant side, a little below shoulder height, twisting their
spine, neck and shoulders.

I am convinced that the correct place is in one's centre, at about hip
height, and that the twisting movement required can be generated at the
hips.

Funnily enough, AJP over there --- has guessed what it might be about;
the demonstration is for an Aikido class.

If you hang around with Aikido people you may notice that they have an
uncanny knack of opening unopenable jam jars and other seized-up items,
a knack that has nothing to do with strength or mystical powers but with
body alignment.

On a related note, one of our students - who is also studying for a
degree in physiotherapy - said she got a funny look from one of the
tutors on her course when she was handling a patient's limb.

"Do you do Aikido, by any chance?" the tutor asked. And when she asked
him how he could tell, he said "Because of the way you lined up all your
bones."

Daniele

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.

MBQ

On Fri, 12 Dec 2008 14:13:23 +0000,
(D.M. Procida) wrote:

snip

Funnily enough, AJP over there --- has guessed what it might be about;
the demonstration is for an Aikido class.

If you hang around with Aikido people you may notice that they have an
uncanny knack of opening unopenable jam jars and other seized-up items,
a knack that has nothing to do with strength or mystical powers but with
body alignment.

In other words, give it some Nikkyo!
Or is it Sankyo??

Regards,


--
Steve ( out in the sticks )
Email: Take time to reply: timefrom_usenet{at}gmx.net

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

D.M. Procida wrote:
Tim Downie wrote:

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. It
will spoil my demonstration if the jar can be twisted open easily.

Interesting, but is it true? I'd need some convincing that we would
contort into a less efficient position when trying to increase
effort. I'd be more inclined to concede that it might *look* like
it's less efficient.

Most people trying to twist open a tight container will hold it
towards their dominant side, a little below shoulder height, twisting
their spine, neck and shoulders.

I am convinced that the correct place is in one's centre, at about hip
height, and that the twisting movement required can be generated at
the hips.

Hmmm, what gives you this conviction? Ya see, if I was a betting man and
had to choose between what "feels right" or someone's "idea" of what is the
most efficient way, I'd plump for what "feels right" most of the time.

How a person holds it may well be dependant on the strength of their
"accessory" muscles, i.e. those that are brought into to play as "second
line" help so to speak. People will vary in the strength of these muscles
and their choice might just be a reflection of the strength these muscles.

If you were to do a study with openable jars (or at least ones that could
only be opened with a deal of difficulty), you might be able to show that
one technique worked more often than another. Just observing how people
attempt to open an unopenable jar doesn't really prove anything other than
the fact that different people use different approaches.

Tim

Stephen Howard wrote:

Funnily enough, AJP over there --- has guessed what it might be about;
the demonstration is for an Aikido class.

If you hang around with Aikido people you may notice that they have an
uncanny knack of opening unopenable jam jars and other seized-up items,
a knack that has nothing to do with strength or mystical powers but with
body alignment.

In other words, give it some Nikkyo!
Or is it Sankyo??

I think it's just walking, actually.

Daniele

Tim Downie wrote:

Interesting, but is it true? I'd need some convincing that we would
contort into a less efficient position when trying to increase
effort. I'd be more inclined to concede that it might *look* like
it's less efficient.

Most people trying to twist open a tight container will hold it
towards their dominant side, a little below shoulder height, twisting
their spine, neck and shoulders.

I am convinced that the correct place is in one's centre, at about hip
height, and that the twisting movement required can be generated at
the hips.

Hmmm, what gives you this conviction? Ya see, if I was a betting man and
had to choose between what "feels right" or someone's "idea" of what is the
most efficient way, I'd plump for what "feels right" most of the time.

What feels right is learned. What's the right way to hold a pen, use a
screwdriver, type on a keyboard, lift sleeping child or open a door?

If you were to do a study with openable jars (or at least ones that could
only be opened with a deal of difficulty), you might be able to show that
one technique worked more often than another. Just observing how people
attempt to open an unopenable jar doesn't really prove anything other than
the fact that different people use different approaches.

Except that certain ways of doing things are demonstrably stronger than
others.

Daniele

On Fri, 12 Dec 2008 14:08:07 -0000, whisky-dave wrote:

Thinking about it and being right handed I must admit when faces with
such a jar I always tend to try using my left hand as it just seems
easier that way.

Also being right handed(*) I pick up jars with my right hand then use my
left on the lid. I take it this is what the OP means by using the left
hand to open a jar? With a really recalcitrant jar I'll try with both ways
round.

As for the OPs qeustion, I'd go the Araldite route but degrease the jar
and lid well first. Hot melt would set too quickly on the cold glass and
lid. I guess if you got the jar and lid hot in a low oven then applied the
goo you might be able to get it on before it set.

(*) Mostly, knife and fork I'm left handed. Saves all that silly messing
about swapping hands with the fork if only using a fork to eat with.

--
Cheers
Dave.

D.M. Procida wrote:
Tim Downie wrote:

If you were to do a study with openable jars (or at least ones that
could only be opened with a deal of difficulty), you might be able
to show that one technique worked more often than another. Just
observing how people attempt to open an unopenable jar doesn't
really prove anything other than the fact that different people use
different approaches.

Except that certain ways of doing things are demonstrably stronger
than others.

I'm not really arguing with that but your test won't prove that, will it?
If the jar can't be opened, how do you prove that one way is better than
another?

Tim

Tim Downie wrote:

If you were to do a study with openable jars (or at least ones that
could only be opened with a deal of difficulty), you might be able
to show that one technique worked more often than another. Just
observing how people attempt to open an unopenable jar doesn't
really prove anything other than the fact that different people use
different approaches.

Except that certain ways of doing things are demonstrably stronger
than others.

I'm not really arguing with that but your test won't prove that, will it?
If the jar can't be opened, how do you prove that one way is better than
another?

The demonstration is just to make the Aikido students aware of how they
(and other people) use their bodies, even in ordinary everyday
activities, and to invite them to think about it.

To say "conviction" was putting it too strongly. It's a strong hunch.

Daniele

In article , Mike Barnes
writes

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!

In other words, hold the lid and twist the jar. I've told people having
trouble pulling corks out of bottles to hold the cork and twist the
bottle. They are so surprised when it works.

In uk.d-i-y, Tim Downie wrote:
D.M. Procida wrote:
Tim Downie wrote:

If you were to do a study with openable jars (or at least ones that
could only be opened with a deal of difficulty), you might be able
to show that one technique worked more often than another. Just
observing how people attempt to open an unopenable jar doesn't
really prove anything other than the fact that different people use
different approaches.

Except that certain ways of doing things are demonstrably stronger
than others.

I'm not really arguing with that but your test won't prove that, will it?
If the jar can't be opened, how do you prove that one way is better than
another?

You put a strain gauge and recorder in the jar?

Getting it out is left as an exercise for the reader.

--
Mike Barnes

On Fri, 12 Dec 2008 14:33:37 +0000, Stephen Howard wrote:

In other words, give it some Nikkyo!
Or is it Sankyo??

Atemi! Atemi is 99% of Aikido. Oh, you wanted the pickles without broken glass?
So sorry...

I'd roughen the glass threads with sandpaper or a whetstone, degrease with
alcohol, and use an epoxy. And a jar with a proper thread, not just those four
ears bent over, no water or other filling.

And maybe wrap the jar in tape, just in case it does break -- no glass shards on
the mat or hand...


Thomas Prufer

In uk.d-i-y, Mike Tomlinson wrote:
In article , Mike Barnes
writes

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!

In other words, hold the lid and twist the jar.

I'm not sure I agree with that. You're holding the jar and the lid and
you're applying an equal twisting force to each. Until the lid actually
moves, any imbalance is imaginary.

--
Mike Barnes

D.M. Procida wrote:
Tim Downie wrote:

If you were to do a study with openable jars (or at least ones that
could only be opened with a deal of difficulty), you might be able
to show that one technique worked more often than another. Just
observing how people attempt to open an unopenable jar doesn't
really prove anything other than the fact that different people use
different approaches.

Except that certain ways of doing things are demonstrably stronger
than others.

I'm not really arguing with that but your test won't prove that,
will it? If the jar can't be opened, how do you prove that one way
is better than another?

The demonstration is just to make the Aikido students aware of how
they (and other people) use their bodies, even in ordinary everyday
activities, and to invite them to think about it.

Fair enough but it would be so much more useful if you could actually
demonstrate one method's superiority over another.

What you really need a a jam jar with adjustable difficultly. Perhaps fit a
valve to the lid and suck it down to an adjustable level of vacuum. Then
you could clearly demonstrate that one technique would work better than
another (and teach your students something about the scientific process).

Tim

In article , Mike Barnes
writes

I'm not sure I agree with that. You're holding the jar and the lid and
you're applying an equal twisting force to each.

My apologies. I assumed you were referring to the greater amount of
grip that can be applied with the dominant hand to the greater surface
(i.e. the jar rather than the lid.)

In uk.d-i-y, Mike Tomlinson wrote:
In article , Mike Barnes
writes

I'm not sure I agree with that. You're holding the jar and the lid and
you're applying an equal twisting force to each.

My apologies. I assumed you were referring to the greater amount of
grip that can be applied with the dominant hand to the greater surface
(i.e. the jar rather than the lid.)

No need to apologise!

I was thinking, if the OP really wanted to do the world a service, he'd
invent the unopenable can of worms.

--
Mike Barnes

"David Hansen" wrote in message
...
On Fri, 12 Dec 2008 08:58:11 +0000 someone who may be
(D.M. Procida) wrote
this:-

I want to make an unopenable jam jar - one that will resist the
strongest grips.

What's the best way to achieve this?

Do you want the contents, or the jar and the lid and the contents?

Has it already been opened?

If you only want the contents and a proper jar opener will not shift
it then drill a hole in the lid. If the jar has not been opened this
will release the vacuum. If necessary the hole can be enlarged to
remove the lid.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54


The poster is asking the opposite of what you have just answered ...

D.M. Procida wrote:
If you hang around with Aikido people you may notice that they have an
uncanny knack of opening unopenable jam jars and other seized-up items,
a knack that has nothing to do with strength or mystical powers but with
body alignment.

That may be the answer - but I'm not convinced. I, and all the people I
compete against, have no problems with jars etc. It isn't alignment, we
know nothing special.

It's just that many hours of holding onto a rope with high tension in it
does a lot for the strength in your hands.

I'm a dinghy sailor; it would be interesting to know if this was true
of other sports and professions - for example, do brickies ever get
stuck with jars?

Andy