Diamine 30ml 'Ink Samples' Plastic bottles becoming concaved and creating an 'air lock' when left unused...???

[51ISH]

I have a  few of these (but with the 'old label' ) 

 

https://cultpens.com/products/diamine-ink-30ml-bottle?variant=43600812540147

 

They have all been sat unused for a number of years. I noticed today all the 'walls' of the bottles had become 'sucked in' and concaved. When I opened the bottle it was like an 'air lock' had been released giving the sound of a 'pop' / 'soda' bottle had been opened.  Just wondered what would cause this?

Try to keep it simple please, I haven't done Physics since the mid '70''s 🤣🤣🤣  So, anyone that want's go into Boyles Law and similar, this is not the thread for you 🤣🤣

[ParramattaPaul]

16 minutes ago, 51ISH said:

I have a  few of these (but with the 'old label' ) 

 

https://cultpens.com/products/diamine-ink-30ml-bottle?variant=43600812540147

 

They have all been sat unused for a number of years. I noticed today all the 'walls' of the bottles had become 'sucked in' and concaved. When I opened the bottle it was like an 'air lock' had been released giving the sound of a 'pop' / 'soda' bottle had been opened.  Just wondered what would cause this?

Try to keep it simple please, I haven't done Physics since the mid '70''s 🤣🤣🤣  So, anyone that want's go into Boyles Law and similar, this is not the thread for you 🤣🤣

This is just guess mind you, but you said they'v sat unused for years, so I think they've been heated and cooled repeatedly over the years and that has caused them to decrease their internal air pressure causing the walls to bend as the outside air pressure has become greeter.

[51ISH]

1 minute ago, ParramattaPaul said:

This is just guess mind you, but you said they'v sat unused for years, so I think they've been heated and cooled repeatedly over the years and that has caused them to decrease their internal air pressure causing the walls to bend as the outside air pressure has become greeter.

 

Yes, I think that makes a lot of sense   Even just looking at this year my (indoor) barometer has shown huge variations  in air pressure.

[ParramattaPaul]

I neg

21 minutes ago, 51ISH said:

 

Yes, I think that makes a lot of sense   Even just looking at this year my (indoor) barometer has shown huge variations  in air pressure.

I neglected to mention atmospheric pressure changes -- the passing of high or low pressure systems -- as a component, but yes that too could compress the elastic walls of a vessel.  In fact, that is essentially how an aneroid barometer works.

[MidSouthern-Dad]

Water can slowly evaporate through the walls of plastic containers.  That’s why you sometimes see never opened ink cartridges run low or even dry.

 

A lot of us will transfer ink from plastic containers into empty glass ink bottles for this reason.

[51ISH]

7 minutes ago, ParramattaPaul said:

I neg

I neglected to mention atmospheric pressure changes -- the passing of high or low pressure systems -- as a component, but yes that too could compress the elastic walls of a vessel.  In fact, that is essentially how an aneroid barometer works.

 

I would think the temperature hardly ever falls below 20'C in my house even overnight 🤣 I can't stand 'the cold' If I'm home during the day it's always at least 23'C 😁 The Utility companies love me....

[txomsy]

If I were to guess...

 

That's typical when you change altitudes. I suppose you haven't moved, which might explain it, but it might (just might) be possible they were at some point open and closed at a lower atmospheric pressure than the one there is now.

 

This could even have been the pressure when they were originally filled.

 

With time the plastic walls may have slowly yielded to the external pressure (or have weakened so that they might be now more sensible to changes in external pressure).

 

A wilder explanation might be a Maxwell's daemon. If the plastic behaves as a semi-permeable membrane, the bottles may have lost some ink component (say, water) without letting other molecules (air components) to enter and with it reduced the inner pressure. But I do not know if that plastic can allow water out without allowing air in. The plastic in cartridges certainly doesn't behave that way, for otherwise, evaporated cartridges would have shrunk to the volume of the remaining ink, which I have never seen (and I've had cartridges almost completely evaporated).

 

I've seen similar behavior with other ink bottles, but then there had been moves between different altitudes in between, so I always thought it was a difference in air pressure.

 

And I've also seen it when traveling and changing altitudes.

But, in any case, the underlying reason is a difference in pressure between the inner and outer sides.

[51ISH]

5 minutes ago, MidSouthern-Dad said:

Water can slowly evaporate through the walls of plastic containers.  That’s why you sometimes see never opened ink cartridges run low or even dry.

 

A lot of us will transfer ink from plastic containers into empty glass ink bottles for this reason.

 

Don't get me started on cartridges running low or dry....I've never got so covered in ink trying to 'rehydrate' some recently

[51ISH]

4 minutes ago, txomsy said:

If I were to guess...

 

That's typical when you change altitudes. I suppose you haven't moved, which might explain it, but it might (just might) be possible they were at some point open and closed at a lower atmospheric pressure than the one there is now.

 

This could even have been the pressure when they were originally filled.

 

With time the plastic walls may have slowly yielded to the external pressure (or have weakened so that they might be now more sensible to changes in external pressure).

 

A wilder explanation might be a Maxwell's daemon. If the plastic behaves as a semi-permeable membrane, the bottles may have lost some ink component (say, water) without letting other molecules (air components) to enter and with it reduced the inner pressure. But I do not know if that plastic can allow water out without allowing air in. The plastic in cartridges certainly doesn't behave that way, for otherwise, evaporated cartridges would have shrunk to the volume of the remaining ink, which I have never seen (and I've had cartridges almost completely evaporated).

 

I've seen similar behavior with other ink bottles, but then there had been moves between different altitudes in between, so I always thought it was a difference in air pressure.

 

And I've also seen it when traveling and changing altitudes.

But, in any case, the underlying reason is a difference in pressure between the inner and outer sides.

 

@txomsy All that talk of altitude pressure changes is bordering on Boyles Law my friend 🤣 I haven't moved houses since the ink was delivered and I haven't taken them SCUBA diving either 🤣  I hope you realize I'm just kidding, and thank you for your reply

[ParramattaPaul]

38 minutes ago, 51ISH said:

 

@txomsy All that talk of altitude pressure changes is bordering on Boyles Law my friend 🤣 I haven't moved houses since the ink was delivered and I haven't taken them SCUBA diving either 🤣  I hope you realize I'm just kidding, and thank you for your reply

No, you haven't moved, but you had the ink for 'donkeys' as you said.  Small pressure/temperature changes can cause expansion and shrinkage over an extensive period of time that accrues sufficiently to become noticeable.  

[51ISH]

7 minutes ago, ParramattaPaul said:

No, you haven't moved, but you had the ink for 'donkeys' as you said.  Small pressure/temperature changes can cause expansion and shrinkage over an extensive period of time that accrues sufficiently to become noticeable.  

 

Luckily the Diamine Sherwood Green seems to be behaving as well as it always did I've released the 'air locks'. I'll try to keep a better eye on them in future.

[The Elevator]

It’s a lot easier for an increase in internal pressure relative to the outside world to force air out, than it is for a decrease in the internal pressure to suck air in.
 

This is because the pressurized bottle can lift the cap by a microscopic amount of distance, and allow the air to escape. A vacuumed bottle will simply suck the cap down tighter so no air will re-enter. 

 

so repeated fluctuations in outside air pressure or temperature can cause an overall shrinking effect.

[51ISH]

7 minutes ago, The Elevator said:

It’s a lot easier for an increase in internal pressure relative to the outside world to force air out, than it is for a decrease in the internal pressure to suck air in.
 

This is because the pressurized bottle can lift the cap by a microscopic amount of distance, and allow the air to escape. A vacuumed bottle will simply suck the cap down tighter so no air will re-enter. 

 

so repeated fluctuations in outside air pressure or temperature can cause an overall shrinking effect.

 

Thank you for keeping the explanation so even I could understand.

[ParramattaPaul]

5 hours ago, The Elevator said:

It’s a lot easier for an increase in internal pressure relative to the outside world to force air out, than it is for a decrease in the internal pressure to suck air in.
 

This is because the pressurized bottle can lift the cap by a microscopic amount of distance, and allow the air to escape. A vacuumed bottle will simply suck the cap down tighter so no air will re-enter. 

 

so repeated fluctuations in outside air pressure or temperature can cause an overall shrinking effect.

Well said.

 

[txomsy]

You do not need to go scuba or climbing to see visible changes. But one needs to change a few hundred meters. In any case, I assumed you didn't, but you still have atmospheric pressure changes. They are small, maybe unnoticeable, but they are. Plastic is flexible and, as all materials, suffers fatigue. After a long time suffering expansion/contraction it will weaken and become more sensible to changes until it may become visible.

 

It is like invisible fingers periodically pushing. Or sunlight on exposed plastics. The effect becomes evident after some (long) time. And on unexposed is the same. Think the plastic lining of car doors: it may take 10 years, but in the end it falls off.

 

I hadn't thought of the cap.