Yesterday, after struggling to open a glass jar,
I resorted to a knife to pry it open. Not for the first time.

Which got me wondering, how do they evacuate the
jar, before screwing on the lid?

Another thought, a survey of public science illiteracy,
ask: is the lid stuck because it's pressurized, or
evacuated? What would be the proportion of replies?

--
Rich

onsdag den 4. januar 2023 kl. 00.54.51 UTC+1 skrev RichD:
> Yesterday, after struggling to open a glass jar,
> I resorted to a knife to pry it open. Not for the first time.
>
> Which got me wondering, how do they evacuate the
> jar, before screwing on the lid?

they put the lid on while it is hot ...

Lasse Langwadt Christensen wrote:
> onsdag den 4. januar 2023 kl. 00.54.51 UTC+1 skrev RichD:
>> Yesterday, after struggling to open a glass jar,
>> I resorted to a knife to pry it open. Not for the first time.
>>
>> Which got me wondering, how do they evacuate the
>> jar, before screwing on the lid?
>
> they put the lid on while it is hot ...
>

It's often the polymer layer on the sealing surface or the threads.
Turning the jar over and banging it firmly on a countertop will often
get it loose.

And of course one can always use the 'blue wrench'. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On 2023-01-03, RichD <r_delaney2001@yahoo.com> wrote:
>
> Yesterday, after struggling to open a glass jar,
> I resorted to a knife to pry it open. Not for the first time.
>
> Which got me wondering, how do they evacuate the
> jar, before screwing on the lid?

They just top it off with steam instead of air, then as the steam cools
it condenses causing a partial vacuum, the steam is often a side-effect
of the production process.

> Another thought, a survey of public science illiteracy,
> ask: is the lid stuck because it's pressurized, or
> evacuated? What would be the proportion of replies?

You left out "friction" and "glue"

--
Jasen.
pǝsɹǝʌǝɹ sʇɥƃᴉɹ ll∀

On January 3, Jasen Betts wrote:
>> Yesterday, after struggling to open a glass jar,
>> I resorted to a knife to pry it open. Not for the first time.
>> Which got me wondering, how do they evacuate the
>> jar, before screwing on the lid?
>
> They just top it off with steam instead of air, then as the steam cools
> it condenses causing a partial vacuum, the steam is often a side-effect
> of the production process.

duh!
If I didn't sleep through my chem classes, I'd know these things.

>> Another thought, a survey of public science illiteracy,
>> ask: is the lid stuck because it's pressurized, or
>> evacuated? What would be the proportion of replies?
>
> You left out "friction" and "glue"

That's possible. But in my experience, I always hear a hiss,
as air enters.

--
Rich

On 04-Jan-23 10:58 am, Lasse Langwadt Christensen wrote:
> onsdag den 4. januar 2023 kl. 00.54.51 UTC+1 skrev RichD:
>> Yesterday, after struggling to open a glass jar,
>> I resorted to a knife to pry it open. Not for the first time.
>>
>> Which got me wondering, how do they evacuate the
>> jar, before screwing on the lid?
>
> they put the lid on while it is hot ...
>
Indeed, it's an essential part of the process. The food has to be hot
enough to be sterile when the lid is put on. That way there's nothing
alive inside to make the food go bad.

Sylvia.

On 1/4/2023 6:20 PM, Sylvia Else wrote:
> On 04-Jan-23 10:58 am, Lasse Langwadt Christensen wrote:
>> onsdag den 4. januar 2023 kl. 00.54.51 UTC+1 skrev RichD:
>>> Yesterday, after struggling to open a glass jar,
>>> I resorted to a knife to pry it open. Not for the first time.
>>>
>>> Which got me wondering, how do they evacuate the
>>> jar, before screwing on the lid?
>>
>> they put the lid on while it is hot ...
>>
> Indeed, it's an essential part of the process. The food has to be hot enough to
> be sterile when the lid is put on. That way there's nothing alive inside to
> make the food go bad.

Indeed, if one sees a *bulging* container, it may be indicative of
anaerobic bacteria having a picnic.

For "home canning" the jars are intentionally designed with lids that
facilitate this process -- the top of the lid is a separate, isolated
surface (from the threaded ring that will eventually secure it to
the jar) so the lid can be loosely attached to still warm jars
and gravity will ensure the top portion adheres to the top of the
jar despite the threaded portion of the lid being "not tight".

On Tuesday, January 3, 2023 at 7:32:29 PM UTC-5, Phil Hobbs wrote:

> >
> It's often the polymer layer on the sealing surface or the threads.

It is? What polymer layer would that be?

> Turning the jar over and banging it firmly on a countertop will often
> get it loose.

Run hot water over lid and it becomes easily removable.

>
> And of course one can always use the 'blue wrench'. ;)

The factory has a sizeable vacuum chamber room into which large numbers of trays full of jars are placed. The lids are placed on the jars to only partially engage the thread so they allow free passage of air. Vacuum is pulled and then IT LOOKS LIKE TO ME the evacuation process causes the lids to jump the threads into a tightly closed position. See lug lids in link below. Vacuum chamber won't work with continuous thread lids. There is a glass packaging institute GPI that specs out the thread drawings for all things glass containers used by industry. So we have this ingenious innovation in jar tops that screw and pop into and out of place, the lug lid.
Heat is mainly used for pasteurization.

The internet is a wonderful thing:
https://eeasylid.com/continuous-thread-vs-lug-lid-whats-the-difference/

>
> Cheers
>
> Phil Hobbs
>
> --
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC / Hobbs ElectroOptics
> Optics, Electro-optics, Photonics, Analog Electronics
> Briarcliff Manor NY 10510
>
> http://electrooptical.net
> http://hobbs-eo.com

On Wednesday, January 4, 2023 at 8:20:19 PM UTC-5, Sylvia Else wrote:
> On 04-Jan-23 10:58 am, Lasse Langwadt Christensen wrote:
> > onsdag den 4. januar 2023 kl. 00.54.51 UTC+1 skrev RichD:
> >> Yesterday, after struggling to open a glass jar,
> >> I resorted to a knife to pry it open. Not for the first time.
> >>
> >> Which got me wondering, how do they evacuate the
> >> jar, before screwing on the lid?
> >
> > they put the lid on while it is hot ...
> >
> Indeed, it's an essential part of the process. The food has to be hot
> enough to be sterile when the lid is put on. That way there's nothing
> alive inside to make the food go bad.

Uh-huh... the main culprit is this lethal thing called botulism. This may come a surprise to you, but botulism is one of the most ubiquitous soil bacteria extant. Hey, guess what? Most canned food is grown in soil. Food is grown in soil- soil contains botulism- get it? get it? Seal that bacteria up in an oxygen free atmosphere and it takes off like there's no tomorrow. Unless the product is acidic- hence all the pickling (vinegar) used in home canning.

https://www.who.int/news-room/fact-sheets/detail/botulism

>
> Sylvia.

On Wednesday, January 4, 2023 at 7:13:34 PM UTC-8, Fred Bloggs wrote:
> On Tuesday, January 3, 2023 at 7:32:29 PM UTC-5, Phil Hobbs wrote:
>
> > >
> > It's often the polymer layer on the sealing surface or the threads.

> It is? What polymer layer would that be?

The frequently-seen aluminized seal atop catsup bottles etc.
is a masterpece of electrical engineering. Plastic bottle, plastic cap,
but the seal is an electrical subcircuit, with sticky plastic as output.

<https://www.enerconind.com/sealing/cap-sealers/super-seal-jr.aspx>

On a sunny day (Thu, 5 Jan 2023 12:20:11 +1100) it happened Sylvia Else
<sylvia@email.invalid> wrote in <k1mmubF5l22U2@mid.individual.net>:

>On 04-Jan-23 10:58 am, Lasse Langwadt Christensen wrote:
>> onsdag den 4. januar 2023 kl. 00.54.51 UTC+1 skrev RichD:
>>> Yesterday, after struggling to open a glass jar,
>>> I resorted to a knife to pry it open. Not for the first time.
>>>
>>> Which got me wondering, how do they evacuate the
>>> jar, before screwing on the lid?
>>
>> they put the lid on while it is hot ...
>>
>Indeed, it's an essential part of the process. The food has to be hot
>enough to be sterile when the lid is put on. That way there's nothing
>alive inside to make the food go bad.
>
>Sylvia.

There are endless series on Smithonian Channel about how food is made in factories.
Nice and sometimes huge machines...
Satellite dish is all you need.
They go into fighter planes and all sort of stuff too.

RichD <r_delaney2001@yahoo.com> wrote in news:f3bdb417-cf95-450e-
8283-5dae0099519bn@googlegroups.com:

>
> Yesterday, after struggling to open a glass jar,
> I resorted to a knife to pry it open. Not for the first time.
>
> Which got me wondering, how do they evacuate the
> jar, before screwing on the lid?
>
> Another thought, a survey of public science illiteracy,
> ask: is the lid stuck because it's pressurized, or
> evacuated? What would be the proportion of replies?
>
> --
> Rich
>

It is not a full vacuum. Just 'some' negative pressure. The media
placed into the hot jar is hot and the air during capping is as well.
When it cools, it pulls a "partial vacuum" on the head space in the
jar. The same way "Mason Jars" work. I did not believe it was that
easy, but it is.

In order to open such a jar, which uses a thick, soft polymer as a
gasket material and does not like to readily realease, Turn it upside
down and rap it sharply on the ass end with the palm of your hand.
If this process worries you, have someone who knows about it show
you. It does not take a very hard rap. Anyway, afterward the lid
comes off easy. The rap of your hand creates a shock wave that
causes a momentary breech of the gasket, freeing it up compared to
its long term sealed position.

Things which are packaged cold can be lidded inside a special
chamber incorporated into the lidding machine.

Carbonated beverages utilize positive pressure, which they
themselves generate in the "head space" of the "pressure vessel" that
is a soda bottle.

Lasse Langwadt Christensen <langwadt@fonz.dk> wrote in news:29c0e39a-
da77-4f88-9ddf-3f4d14e80f25n@googlegroups.com:

> onsdag den 4. januar 2023 kl. 00.54.51 UTC+1 skrev RichD:
>> Yesterday, after struggling to open a glass jar,
>> I resorted to a knife to pry it open. Not for the first time.
>>
>> Which got me wondering, how do they evacuate the
>> jar, before screwing on the lid?
>
> they put the lid on while it is hot ...
>
>

Hey! Do you know what the origin for the Ball Drop in New York City
on New Years Day is?

Neil DeGrasse Tyson does. Cool little vid about it.

<https://www.youtube.com/watch?v=6XhRjh4CLtw>

On Thursday, January 5, 2023 at 7:11:23 AM UTC-5, DecadentLinux...@decadence.org wrote:
> RichD <r_dela...@yahoo.com> wrote in news:f3bdb417-cf95-450e-
> 8283-5dae...@googlegroups.com:
> >
> > Yesterday, after struggling to open a glass jar,
> > I resorted to a knife to pry it open. Not for the first time.
> >
> > Which got me wondering, how do they evacuate the
> > jar, before screwing on the lid?
> >
> > Another thought, a survey of public science illiteracy,
> > ask: is the lid stuck because it's pressurized, or
> > evacuated? What would be the proportion of replies?
> >
> > --
> > Rich
> >
> It is not a full vacuum. Just 'some' negative pressure. The media
> placed into the hot jar is hot and the air during capping is as well.
> When it cools, it pulls a "partial vacuum" on the head space in the
> jar. The same way "Mason Jars" work. I did not believe it was that
> easy, but it is.

Not really. It's a very detailed oriented process:

UDA 2005 survey:

A national survey of home canners finds that up to 57% use methods deemed unsafe by USDA standards

https://www.nal.usda.gov/exhibits/ipd/canning/timeline-table

"Normal thorough cooking (pasteurisation: 70°C 2min or equivalent) will kill Cl.botulinum bacteria but not its spores. To kill the spores of Cl.botulinum a sterilisation process equivalent to 121°C for 3 min is required. The botulinum toxin itself is inactivated (denatured) rapidly at temperatures greater than 80°C . "

121C would be 212+ 1.8 x 21= 250oF. You're not going to get that in a water bath, you need a pressure cooker. And it's beyond critical that every little thing be thoroughly sterilized before use.

https://www.fsai.ie/faq/botulism.html#:~:text=botulinum%20a%20sterilisation%20process%20equivalent,greater%20than%2080%C2%B0C%20.

On Thursday, January 5, 2023 at 12:35:10 AM UTC-5, whit3rd wrote:
> On Wednesday, January 4, 2023 at 7:13:34 PM UTC-8, Fred Bloggs wrote:
> > On Tuesday, January 3, 2023 at 7:32:29 PM UTC-5, Phil Hobbs wrote:
> >
> > > >
> > > It's often the polymer layer on the sealing surface or the threads.
>
> > It is? What polymer layer would that be?
> The frequently-seen aluminized seal atop catsup bottles etc.
> is a masterpece of electrical engineering. Plastic bottle, plastic cap,
> but the seal is an electrical subcircuit, with sticky plastic as output.
>
> <https://www.enerconind.com/sealing/cap-sealers/super-seal-jr.aspx>

That's pretty fast!

On 1/5/2023 7:27 AM, DecadentLinuxUserNumeroUno@decadence.org wrote:
> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote in news:29c0e39a-
> da77-4f88-9ddf-3f4d14e80f25n@googlegroups.com:
>
>> onsdag den 4. januar 2023 kl. 00.54.51 UTC+1 skrev RichD:
>>> Yesterday, after struggling to open a glass jar,
>>> I resorted to a knife to pry it open. Not for the first time.
>>>
>>> Which got me wondering, how do they evacuate the
>>> jar, before screwing on the lid?
>>
>> they put the lid on while it is hot ...
>>
>>
>
> Hey! Do you know what the origin for the Ball Drop in New York City
> on New Years Day is?
>
> Neil DeGrasse Tyson does. Cool little vid about it.
>
> <https://www.youtube.com/watch?v=6XhRjh4CLtw>

Thanks!
Ed