4 hours ago, TheVat said:

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

Never heard that, the only thing that colours my urine is Marrowfat peas.

19 minutes ago, pinball1970 said:

Never heard that, the only thing that colours my urine is Marrowfat peas.

When I was a tiny boy I loved beetroot and my parents did in fact once call the doctor because my urine went pink. Betanin:

A zwitterion, apparently, at least at some pH values.

P.S. Diagram seems to have an error, the O substituent on the ring joined to the sugar should be OH.

Edited November 22Nov 22 by exchemist

13 minutes ago, studiot said:

58 minutes ago, exchemist said:

When I was a tiny boy I loved beetroot and my parents did in fact once call the doctor because my urine went pink.

Yes ,I buy beetroot juice and a small amount drunk cold is quite nice.

Except,a while back (perhaps I had the remains of a cold) I coughed up what looked like blood into the sink.It took me a while to realize it was beetroot juice lodged in my throat.

And ,yes it does turn urine and stools red or pink quite promptly.

Edited November 22Nov 22 by geordief

13 hours ago, exchemist said:

my urine went pink. Betanin:

I have been trying to eat more Beetroot, so I will check my urine next time I have a significant amount.

21 hours ago, pinball1970 said:

Never heard that, the only thing that colours my urine is Marrowfat peas.

Well, the drumming thing apparently relates to red corpuscles in the hand splitting and then the iron-rich contents passing through the kidneys and excreted.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3213680/

On 11/22/2025 at 10:31 AM, geordief said:

Looks a bit like an emasculator for animals.

Heh. Or men, if they're forced to admit they used it to open a jar. 😄

Edited November 23Nov 23 by TheVat

On 11/21/2025 at 5:07 PM, 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.

All you needed was a screwdriver.. quick and easy.. pry off the lid and let air in, and once the pressure is equalized, you can unscrew it without any problems.

On 11/21/2025 at 5:29 PM, geordief said:

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

That's a bad idea because you'll ruin the lid.

On 11/21/2025 at 5:29 PM, geordief said:

It also helps if hands and lid are very dry.

You're right here. Jars are easier to open if you put a cloth on them first.

Just now, geordief said:

  On 11/21/2025 at 4:07 PM, studiot said:

L

37 minutes ago, Sensei said:

All you needed was a screwdriver.. quick and easy.. pry off the lid and let air in, and once the pressure is equalized, you can unscrew it without any problems

Be careful.Screwdrivers can slip very easily.The glass itself is very slippy and you don't want the end of the screwdriver going into your wrist .

It can be frustrating if you are not used to it and your attention can skip a beat.

Maybe hold the jar upside down on a flat surface?

Come on !
We are on the second page of discussion on opening jars ?
Some of the members here can probably calculate the trajectory for a moon landing.

I didn't think jar lids would be such a problem; most housewives can manage 😄 .
( I can imagine the problems you guys have doing laundry )

1 hour ago, MigL said:

;most housewives can manage 😄 .

Debatable (a separate thread?)

12 hours ago, MigL said:

Come on !
We are on the second page of discussion on opening jars ?
Some of the members here can probably calculate the trajectory for a moon landing.

I didn't think jar lids would be such a problem; most housewives can manage 😄 .
( I can imagine the problems you guys have doing laundry )

Would any of those who favour the low pressure theory care to offer a mechanics explanation as to how a pressure differential developes the necessary restraining torque on the cap ?

Here also is another picture this time of a marmalade jar.

The new jar shows the cap in its unopened state, looking like thousands of other such lids with one-piece lids.
And the particular supplier used to use that type of cap with several clutch tabs forced onto the ridges in the glass.

But the supplier has recently changed to a two piece lid for reasons I don't understand,
A dismantled new lid (sorry I had to distort it to get it apart) is also shown in the photograph.

I can't see the gain to the manufactured that more than offsets the extra manufacturing steps necessary to fit the lids in this way.

I am also not sure if the lids are mechanically crimped onto the jars or are fitted hot and allowed to shrink on cooling.

Either way I think the restraining friction is a result of this clamping force.

I have used the two-part lids.
They usually come with Mason jars, used for 'canning' home-made preserves such as jams, peach slices in syrup, cherries in alcohol, even pickeled vegetables or tomato/pasta sauce ( I used to help my mom when I was young ).

They are similar in operation to the other 'tabbed' lids, and both have a rubber friction ring where the lid contacts the glass.
The usual procedure is to fill with hot preserves and cap tightly with the threaded ring, on the now soft rubber sealing surface of the lid.
As the contents ( and the rubber seal ) cool, the head space will now be at a lower pressure than atmospheric and the seal will re-harden to provide a not-easily slipping seal.
The seal is almost always good enough that the threaded ring part of the two-part lid can be removed without loss of seal for years, and the ring re-used for next year's canning ( for the frugal among us ); however the lid part cannot be re-used, but they are available separately without the threaded ring.

I keep my jam/marmalade in the refrigerator once opened, and putting them back in the fridge to cool again after use, makes them very hard to open the next time.
A little bit of differential pressure makes for a good seal.
FYI Airplane doors are not 'locked'; it is their design ( 'plug' ), and a couple of pounds of DP, that keeps them from opening, although there have been one or two occasions where a 'crazed' passenger has managed to open a door and depressurize the plane ( probably at lower altitudes ).

Yes I fully agree that a vacuum seal is developed.

But the seal is separate from the clamping force, as shown in this video from Kilner.

Kilner jars are the Uk equivalent of your Mason type.

They are for home preserving, not commercial practice.

The difference being that the commercial jars and lids are not designed for reuse and their 'screw' down force is minimal, unlike the home variety.

This video is very clear.

On 11/23/2025 at 11:28 PM, geordief said:

Be careful.Screwdrivers can slip very easily.The glass itself is very slippy and you don't want the end of the screwdriver going into your wrist .

It's physically impossible. You're holding the jar in your left hand, so your hand is holding it from behind, and your right hand is holding the screwdriver. You can't hurt either wrist.

Insert a screwdriver (only a flathead/minus type) into the gap between the jar and the lid, and gently turn it clockwise until you hear the hiss of air entering the jar. It's just a millimeter to the right. Once the pressure has equalized, you can unscrew the lid. There's no hocus pocus involved. You don't need to be a nuclear physicist to know how to open a jar.

I open beer bottles like this every day.

Edited November 26Nov 26 by Sensei