Some manufacturers really seal their jar tops on tightly.

So most of my family can't open them.

Up to recently I have managed to supply the neccessary brute force, but I am getting older.

Once technique I can really recommend is to use a hair drier, on max, bot perhaps 30 second to 1 minute.
Play this directly onto the metal top only.
the metal wi;; heat up quickly and expand, but the glass will not so voila.

The result is a dead easy to open jar.

Cool. I'm also the jar opener in my house, and also getting older (seems to be a common thing in human existence). I also recommend the shock method - tap the edge of lid against something, which seems to slightly disengage the threads. (Obv not too vigorously, if it's a glass jar)

Various heat methods work, I gather, because metal has a greater coefficient of expansion than glass or plastics.

17 minutes ago, studiot said:

Some manufacturers really seal their jar tops on tightly.

So most of my family can't open them.

Up to recently I have managed to supply the neccessary brute force, but I am getting older.

Once technique I can really recommend is to use a hair drier, on max, bot perhaps 30 second to 1 minute.
Play this directly onto the metal top only.
the metal wi;; heat up quickly and expand, but the glass will not so voila.

The result is a dead easy to open jar.

I always make a small hole with a ( hopefully short) sharp knife if they are too tight.

It may still require strength even after that.

It also helps if hands and lid are very dry.

Part of the issue is because the contents are put in hot then sealed. The airspace cools down and creates a partial vacuum, increasing the friction at the screw thread interfaces. As suggested, you can heat it up to equalise the pressure, or pop a hole in the lid.

14 minutes ago, StringJunky said:

Part of the issue is because the contents are put in hot then sealed. The airspace cools down and creates a partial vacuum, increasing the friction at the screw thread interfaces. As suggested, you can heat it up to equalise the pressure, or pop a hole in the lid.

Interesting. Which is the more significant effect, coefficient of expansion of metal threads, or raising pressure in the airspace?

The hole method has a downside if it's a jam jar and your fridge is not the cleanest. Those wee spores find their way in there.

15 minutes ago, TheVat said:

Interesting. Which is the more significant effect, coefficient of expansion of metal threads, or raising pressure in the airspace?

The hole method has a downside if it's a jam jar and your fridge is not the cleanest. Those wee spores find their way in there.

StudioT can probably answer that. Maybe sticking a label or tape over the hole should suffice? I'm only thinking of a pinhole.

Edited November 21Nov 21 by StringJunky

11 minutes ago, StringJunky said:

  25 minutes ago, TheVat said:

Interesting. Which is the more significant effect, coefficient of expansion of metal threads, or raising pressure in the airspace?

The hole method has a downside if it's a jam jar and your fridge is not the cleanest. Those wee spores find their way in there.

StudioT can probably answer that. Maybe sticking a label or tape over the hole should suffice? I'm only thinking of a pinhole.

Or perhaps using the lid from a previous jar from when you were younger and stronger.

19 minutes ago, StringJunky said:

StudioT can probably answer that. Maybe sticking a label or tape over the hole should suffice? I'm only thinking of a pinhole.

Even a pinhole is a gaping chasm for air / microbe mix under pressure.

And I don't usually have handy hardened pins for puncturing.

The glass and contents do not heat up as quickly as the metal for two reasons.

Firstly they both have a much lower heat transfer coefficient than metal soit take longer for the heat to penetrate.

Secondly it take more heat to heat up as they both have a higher heat capacity.

Any air in the top of the jar will also heat up quite quickly from the metal and so the pressure diferential will be lower.

22 minutes ago, KJW said:

Or perhaps using the lid from a previous jar from when you were younger and stronger.

😄

I never thought of that, when I was younger and stronger.

Silly me.

+1

But seriously with all these politically rather than scientifically ways of saving the planet - or cynically saving the manufacturers a few coppers -

many liquid/semi liwuid products like youghurt used to come in plastic pots, womplete with a replaceable plastic lid over the seal.
Nowadays they have dropped the plastic lid ( a very minot % of the total plastic in the packaging.
to great inconvenience of customers.

We are fast running out of old lids that have been rewashed many times (you can only rewash so many times)

Edited November 21Nov 21 by studiot

I used to have a rubber band that could fit the rim of the lid with a bit of stretching. That improves the grip considerably and makes opening easier. For many years I had the strongest grip in the house as a result of years of rowing, but it is weakening now that I am over 70. Must get another rubber band, before the marmalade jar defeats me…..

1 hour ago, KJW said:

Or perhaps using the lid from a previous jar from when you were younger and stronger.

Good one! LOL. Alas, our younger and stronger selves didn't quite believe they would get older and weaker. I remember when young how many sort of imagined (quite irrationally) that they would be amazing and exceptional old folks, outliers who would get up every day and go water skiing or rock climbing. It's part of that whole Off the Bell Curve delusion where people imagine themselves exceptional and (as a US radio show guy used to say "all the children are above-average"). It's a cousin of Dunning Krueger.

1 hour ago, TheVat said:

Interesting. Which is the more significant effect, coefficient of expansion of metal threads, or raising pressure in the airspace?

The hole method has a downside if it's a jam jar and your fridge is not the cleanest. Those wee spores find their way in there.

I'm sure it is the vacuum inside that is the chief issue. But then the difference in difficulty of apparently identically-sized jars must be due to differences in friction in the threads and seal.

By the way, as we are approaching that time of year, those rubber seals on foie gras jars from France are a bastard. Sometimes I have to resort to pliers to pull the rubber tag enough to break the seal.

Also, avoid putting an unopened jar in the fridge; the metal lid will contract > the jar. This was so effective at further tightening that I had to run hot water on the top over a minute before it would yield. I had stupidly put peanut butter in the fridge directly from the grocery sack. @geordief 's stabbing trick might have helped for that, given that PB is pretty mold resistant.

25 minutes ago, exchemist said:

By the way, as we are approaching that time of year, those rubber seals on foie gras jars from France are a bastard. Sometimes I have to resort to pliers to pull the rubber tag enough to break the seal.

This problem reminds me of the now iconic comedy sketch called White People Problems. My God, man, there are people in this world who would LOVE to struggle with foie gras jars! Related to this - in the US, foie gras started to be viewed as evil in the seventies, as there was all this publicity on how the geese were abused. Did that improve, or did everyone just stop caring? Sorry, a bit OT, perhaps I can do a separate thread if that's not too much of a _____ _______ _____.

47 minutes ago, exchemist said:

Sometimes I have to resort to pliers to pull the rubber tag enough to break the seal.

One drawer in every good kitchen should include several good pairs of scissors, a pair of tongs, a couple of screwdrivers, a couple of pairs of pliers and one or two skewers.

3 hours ago, geordief said:

I always make a small hole with a ( hopefully short) sharp knife if they are too tight.

It only takes a fraction of a millisecond to equalise pressure so a hole is a bit of an overkill. Usually a firm knock with a blunt object (eg hefty screwdriver handle) is enough to momentarily break the seal.

At risk of being Captain Obvious, I trust everyone knows that the left hand is much the stronger for applying anticlockwise torque. Tighten with the right, loosen with the left.

If all else fails, it's worth purchasing a small selection of large jubilee hose clips from your local hardware store. It gives you something you can give a judicious belt with a hammer. Something will give, but quite satisfying either way.

57 minutes ago, studiot said:

One drawer in every good kitchen should include several good pairs of scissors, a pair of tongs, a couple of screwdrivers, a couple of pairs of pliers and one or two skewers.

Also, it will be the drawer that jams shut because your tongs have cross-linked with your pliers and decide to hold down the fort until kingdom come. They also seem to multiply and I might have to give up on the kitchen entirely.

1 hour ago, TheVat said:

Also, avoid putting an unopened jar in the fridge; the metal lid will contract > the jar. This was so effective at further tightening that I had to run hot water on the top over a minute before it would yield. I had stupidly put peanut butter in the fridge directly from the grocery sack. @geordief 's stabbing trick might have helped for that, given that PB is pretty mold resistant.

This problem reminds me of the now iconic comedy sketch called White People Problems. My God, man, there are people in this world who would LOVE to struggle with foie gras jars! Related to this - in the US, foie gras started to be viewed as evil in the seventies, as there was all this publicity on how the geese were abused. Did that improve, or did everyone just stop caring? Sorry, a bit OT, perhaps I can do a separate thread if that's not too much of a _____ _______ _____.

Yeah definitely a 1st World problem, I grant you. But in France, everyone gets in foie gras at Christmastime. And so do my (half-French) son and I, for Réveillon on New Year's Eve, accompanied by Sauternes. (We also do boudins blancs with apples and a chenin blanc on Christmas Eve - though I can't drink much as I have to sing carols, Gregorian chant and a motet or two at Midnight Mass.) I'm now over 70, damn it, and these traditions are something I hang onto increasingly tenaciously. 😄

3 hours ago, exchemist said:

Now that my lousy internet connection has decided to let me see this image...

For those unfamiliar with the design, this is a (small) Kilner jar as mentioned recently in another thread. Don't be too hard on the French on this one. It was invented in Yorkshire.

I usually try a hard 2 hand squeeze first, interlocking my fingers and squeezing with the heel of the palms to push the rim out of round. If that doesn't do it I do like Gordief does - punch a small hole in the lid to release the suction. Depending on contents I might put tape over the hole or transfer to another container.

3 hours ago, CharonY said:

They also seem to multiply and I might have to give up on the kitchen entirely.

Well the screwdrivers are fond of screwing, which is why they also proliferate inside of toolboxes. Best not have more than one in any given drawer or box - they are not parthenogenetic, thankfully.

4 hours ago, sethoflagos said:

Usually a firm knock with a blunt object (eg hefty screwdriver handle) is enough to momentarily break the seal.

My default method. On both jars and cats mating noisily in the yard.

4 hours ago, sethoflagos said:

At risk of being Captain Obvious, I trust everyone knows that the left hand is much the stronger for applying anticlockwise torque. Tighten with the right, loosen with the left.

Not obvious to me, mein Kapitan. Makes complete sense once called to my attention, though.

4 hours ago, sethoflagos said:

If all else fails, it's worth purchasing a small selection of large jubilee hose clips from your local hardware store. It gives you something you can give a judicious belt with a hammer. Something will give, but quite satisfying either way.

Har! I mean, I laugh but I've actually done this with an old jar of electrical parts which had rusted shut over a couple decades. The top of the jar separated, with the neck remaining bonded to the lid. The parts inside were immaculate, so well worth it.

A couple of ways to open those jars:

• insert a strong dining knife in the gap between the spaced lid thread teeth and the glass, and twist. Deforms the lid edge to break the vacuum; a flat screwdriver works too.

• 

• Use those kitchen rubber gloves to turn the lid and hold the jar.

Edited November 22Nov 22 by Externet

7 hours ago, studiot said:

One drawer in every good kitchen should include several good pairs of scissors, a pair of tongs, a couple of screwdrivers, a couple of pairs of pliers and one or two skewers.

All you feeble old men should head down to a nearby dollar store.
They sell a V-shaped contraption that screws onto the bottom of your kitchen cabinets ( out of sight ), and when you need to open a jar lid, you push the jar lid into the V, which has a friction surface, and turn the jar.
Easy-peasy.

Incidentally ... your fingers are weaker than your thumb, so always turn in a direction that tends to 'tighten' your fingers.
( think of a pipe wrench )

Beetroot the worst. A few cc of boiling water, a bit of fast conduction, expansion, tip the water off, a quick wipe, evaporation, some torque, beetroot!

NB water from the kettle on the top not the sides, do it in the sink. Use a tea towel and rubber gloves.

5 hours ago, MigL said:

All you feeble old men

I play drums so I have to look after my hands, they ache after a set these days.

13 hours ago, MigL said:

All you feeble old men should head down to a nearby dollar store.
They sell a V-shaped contraption that screws onto the bottom of your kitchen cabinets ( out of sight ), and when you need to open a jar lid, you push the jar lid into the V, which has a friction surface, and turn the jar.
Easy-peasy

Yep. Also there's the easy-peasy, doesn't even need installation or hot water or ice picks, jar wrench,...

BTW, is it true that drumming with your hands (vs sticks) can cause pink in the urine? This is a question for @pinball1970

1 hour ago, TheVat said:

Yep. Also there's the easy-peasy, doesn't even need installation or hot water or ice picks, jar wrench,...

BTW, is it true that drumming with your hands (vs sticks) can cause pink in the urine? This is a question for @pinball1970

Looks a bit like an emasculator for animals.

2 hours ago, TheVat said:

Yep. Also there's the easy-peasy, doesn't even need installation or hot water or ice picks, jar wrench,...

Those always go missing just when you need them.
When you don't need them, you're tripping over the three extra sets you bought because the originals were missing when you needed them.

Or, maybe you guys are feeble, and I'm forgetful of where I put things.