I thought I’d have a bit of science fun with my 6yo boy (sorry, 6 and a half!) and we built a vacuum chamber. I’ve bought a large glass jar that has a metal lid, a 50ml syringe and tube, and some valves. See pic below…

The problem we are having with it, it isn’t not airtight. I have put in an unopened pack of Smith’s chips and tightly put the lid on. But when we pump the syringe to try and suck out all the air, no matter how long it’s pumped for, there is no change in the chip pack.

I haven’t bought a pressure gauge yet but plan to get one in the next week or so.

The gold valve in the top is closed. Both valves in the lid are held in place with hot glue, and no air holes. The tap on the side has had a rubber o-ring put in place and sealed with hot glue, and the tap itself full of hot glue as well, so no air is getting through there. The only place air could get through is the thread of the metal lid – so I wrapped the thread with that thin blue plumber’s tape stuff that’s supposed to stop drains leaking, and even a line of hot glue around the inside of the lid, but still made no difference. So today removed the glue from the lid and the plumber tape and put a ring of silicone around the inside of the lid, hoping it will be flexible enough to seal it when it’s screwed down.

So firstly, any other ideas how to air-seal it if the silicone hasn’t worked (once dried, I’ll be able to try it)? And secondly, what sort of things should we put in there to try? I did see a YouTube video and would like to try shaving cream :)

JTQ said:

I thought I’d have a bit of science fun with my 6yo boy (sorry, 6 and a half!) and we built a vacuum chamber. I’ve bought a large glass jar that has a metal lid, a 50ml syringe and tube, and some valves. See pic below…

The problem we are having with it, it isn’t not airtight. I have put in an unopened pack of Smith’s chips and tightly put the lid on. But when we pump the syringe to try and suck out all the air, no matter how long it’s pumped for, there is no change in the chip pack.

I haven’t bought a pressure gauge yet but plan to get one in the next week or so.

The gold valve in the top is closed. Both valves in the lid are held in place with hot glue, and no air holes. The tap on the side has had a rubber o-ring put in place and sealed with hot glue, and the tap itself full of hot glue as well, so no air is getting through there. The only place air could get through is the thread of the metal lid – so I wrapped the thread with that thin blue plumber’s tape stuff that’s supposed to stop drains leaking, and even a line of hot glue around the inside of the lid, but still made no difference. So today removed the glue from the lid and the plumber tape and put a ring of silicone around the inside of the lid, hoping it will be flexible enough to seal it when it’s screwed down.

So firstly, any other ideas how to air-seal it if the silicone hasn’t worked (once dried, I’ll be able to try it)? And secondly, what sort of things should we put in there to try? I did see a YouTube video and would like to try shaving cream :)

Try a powerful vacuum cleaner instead of a syringe.

JTQ said:

I thought I’d have a bit of science fun with my 6yo boy (sorry, 6 and a half!) and we built a vacuum chamber. I’ve bought a large glass jar that has a metal lid, a 50ml syringe and tube, and some valves. See pic below…

The problem we are having with it, it isn’t not airtight. I have put in an unopened pack of Smith’s chips and tightly put the lid on. But when we pump the syringe to try and suck out all the air, no matter how long it’s pumped for, there is no change in the chip pack.

I haven’t bought a pressure gauge yet but plan to get one in the next week or so.

The gold valve in the top is closed. Both valves in the lid are held in place with hot glue, and no air holes. The tap on the side has had a rubber o-ring put in place and sealed with hot glue, and the tap itself full of hot glue as well, so no air is getting through there. The only place air could get through is the thread of the metal lid – so I wrapped the thread with that thin blue plumber’s tape stuff that’s supposed to stop drains leaking, and even a line of hot glue around the inside of the lid, but still made no difference. So today removed the glue from the lid and the plumber tape and put a ring of silicone around the inside of the lid, hoping it will be flexible enough to seal it when it’s screwed down.

So firstly, any other ideas how to air-seal it if the silicone hasn’t worked (once dried, I’ll be able to try it)? And secondly, what sort of things should we put in there to try? I did see a YouTube video and would like to try shaving cream :)

marshmallows are good for visual representation of low pressure.

have you got a couple of valves on the line from the syringe? otherwise you are only pulling 50ml out and it won’t be much of a change

Bubblecar said:

Try a powerful vacuum cleaner instead of a syringe.

As much as I’d hate to say it right now, I haven’t got one… I’m having to borrow one at the moment whenever it’s needed.

Stumpy_seahorse said:

marshmallows are good for visual representation of low pressure.

have you got a couple of valves on the line from the syringe? otherwise you are only pulling 50ml out and it won’t be much of a change

Ahh yeh that’d be a good one to try :)

Yeh on the lid, there’s 2 valves going out into the syringe, and 1 valve on the side of the syringe itself to release the air when the plunger (?) is pushed back in. I know it’s not going to be releasing much air with each pump of the syringe, but at the moment it’s the best I’ve got so it’s just a case of sitting there for a little while and pump pump pump pump…. until something happens.

JTQ said:

Stumpy_seahorse said:

marshmallows are good for visual representation of low pressure.

have you got a couple of valves on the line from the syringe? otherwise you are only pulling 50ml out and it won’t be much of a change

Ahh yeh that’d be a good one to try :)

Yeh on the lid, there’s 2 valves going out into the syringe, and 1 valve on the side of the syringe itself to release the air when the plunger (?) is pushed back in. I know it’s not going to be releasing much air with each pump of the syringe, but at the moment it’s the best I’ve got so it’s just a case of sitting there for a little while and pump pump pump pump…. until something happens.

What I’d do, is put a balloon on the valve outlet on the side of the syringe, this way you can show him the amount of air you have removed from the jar

Stumpy_seahorse said:

What I’d do, is put a balloon on the valve outlet on the side of the syringe, this way you can show him the amount of air you have removed from the jar

I didn’t even think of that … I’ll do that as well :)

Stumpy_seahorse said:

JTQ said:

Stumpy_seahorse said:

marshmallows are good for visual representation of low pressure.

have you got a couple of valves on the line from the syringe? otherwise you are only pulling 50ml out and it won’t be much of a change

Ahh yeh that’d be a good one to try :)

Yeh on the lid, there’s 2 valves going out into the syringe, and 1 valve on the side of the syringe itself to release the air when the plunger (?) is pushed back in. I know it’s not going to be releasing much air with each pump of the syringe, but at the moment it’s the best I’ve got so it’s just a case of sitting there for a little while and pump pump pump pump…. until something happens.

What I’d do, is put a balloon on the valve outlet on the side of the syringe, this way you can show him the amount of air you have removed from the jar

Brilliant!

Michael V said:

Stumpy_seahorse said:

JTQ said:

Ahh yeh that’d be a good one to try :)

Yeh on the lid, there’s 2 valves going out into the syringe, and 1 valve on the side of the syringe itself to release the air when the plunger (?) is pushed back in. I know it’s not going to be releasing much air with each pump of the syringe, but at the moment it’s the best I’ve got so it’s just a case of sitting there for a little while and pump pump pump pump…. until something happens.

What I’d do, is put a balloon on the valve outlet on the side of the syringe, this way you can show him the amount of air you have removed from the jar

Brilliant!

I have my moments..

try turning the seal in the syringe around.

> what sort of things should we put in there to try?

Oh you beauty!

We could have done with your help on the SSSF Google X-Prize challenge.

The one thing I’d love to try first is “vacuum welding”. Mechanical movements involve friction between parts, and a really thin layer of air aids that movement enormously. In space, mechanical movement is really dodgy because without that thin layer of air the parts that are supposed to move freely end up welding themselves together. https://en.wikipedia.org/wiki/Vacuum_cementing

The second thing I’d like to try is the degradation of materials in space. Any material with pockets of liquid or gas will de-gas. Start by trying to get different grades of oil to boil at room temperature in the vacuum flask. Does plastic become brittle? What happens with other common liquids, eg. hand wash, honey, mayonnaise?

The third thing I’d like to try is biology experiments. Which animals (plants, fungi, bacteria) can survive at 1/3 atmosphere pressure? Does slow reduction in pressure over a period of a week or more improve the survival rate? Does cooling or heating improve the survival rate?

The fourth thing I’d like to try is … possibly chemical reactions at low pressure. eg. what pressure will extinguish a flame?

mollwollfumble said:

> what sort of things should we put in there to try?

Oh you beauty!

We could have done with your help on the SSSF Google X-Prize challenge.

The one thing I’d love to try first is “vacuum welding”. Mechanical movements involve friction between parts, and a really thin layer of air aids that movement enormously. In space, mechanical movement is really dodgy because without that thin layer of air the parts that are supposed to move freely end up welding themselves together. https://en.wikipedia.org/wiki/Vacuum_cementing

The second thing I’d like to try is the degradation of materials in space. Any material with pockets of liquid or gas will de-gas. Start by trying to get different grades of oil to boil at room temperature in the vacuum flask. Does plastic become brittle? What happens with other common liquids, eg. hand wash, honey, mayonnaise?

The third thing I’d like to try is biology experiments. Which animals (plants, fungi, bacteria) can survive at 1/3 atmosphere pressure? Does slow reduction in pressure over a period of a week or more improve the survival rate? Does cooling or heating improve the survival rate?

The fourth thing I’d like to try is … possibly chemical reactions at low pressure. eg. what pressure will extinguish a flame?

I reckon you’d be pumping that syringe for a very long time for any of those…