Keep Your Drinks Carbonated for Days (DIY Kitchen Accessory)

by NirL

20K18670

Intro: Keep Your Drinks Carbonated for Days (DIY Kitchen Accessory)

In this instructable I'll show you how to make a really simple kitchen accessory to keep your carbonated drinks fizzy for days (and more!) using only air pressure!

There's almost nothing more disappointing than a soda drink with no bubbles. So I thought, there should be a simple solution for this! But I couldn't find one online, so I made one! Some people told me this could be made for profit, but honestly, I don't want to do that :)

Hope you enjoy my project and make your own!

STEP 1: Why Is the CO2 Escaping Only AFTER We Open the Bottle??

Have you ever wondered why carbonated drinks run out of bubbles after a while, but it only happens after we opened the bottle?

The answer has to do with air pressure inside the bottle! It turns out that by keeping the bottle pressurized, bottles cannot form and escape the liquid. This happens because dissolved CO2 takes less volume than CO2 in gas form, and by keeping a the bottle pressurized we're not letting those bubbles expand and form. So, the equilibrium state of the soda bottle is a state where the bubbles are dissolved in the liquid.

When we buy soda bottles they come pressurized (you can feel that the bottle is rock hard), but once we open them the pressure is released and the equilibrium state changes! Now, bubbles want to form and escape the liquid. It's not all bad news! We want this to happen, because otherwise we wouldn't get any fizziness when we drink it! The C02 would remain dissolved for ever.

But what happens when we want to keep the soda drink carbonated for a later time?

Well, if we keep the cap tight, bubbles can still escape the liquid! They keep escaping until the air pressure inside the bottle is high enough to stop them, but if your bottle has enough room in it, plenty of gas can escape the liquid before the formation of bubbles seize. This is why 90% full soda bottles remain carbonated longer than 50% full soda bottles do!

Solution to the Problem - Soda Companies Wished You Didn't Know This!

To stop the bubbles from escaping, we can actively pressurize the bottle (pump air to make the pressure higher) once we're done drinking!

This works like magic - one moment you see bubbles escaping the liquid (practically going to waste!) and a moment later (after you pressurize the bottle) the is no more bubble formation!

STEP 2: Drill a Hole in a Bottle Cap

Drill a hole in the diameter of the air valve. It's better to have a hole that's a little too small than a little to larger. You can always widen the hole with a larger bit or just screw the valve in with some force like I did. I used a wood drill bit, but other drill bits would work as well.

STEP 3: Attach the Air Valve

Screw the air valve in. Make sure the inlet is facing outwards (so you can attach a pump to it later!). Screw it as tight as possible to make sure no gases can escape.

STEP 4: Pressurize!

Once the cap is screwed in, attach an air pump and pressurize. I have a hand-held pump that was built for bicycles and it worked great. Keep pumping until you see the gas bubbles stop forming! And that's it! You're done!

Keeping your beverages cold will also help keeping them carbonated for longer.

STEP 5: You're All Done!

You're all done! The valve I used is supposed to be food-safe, but personally I don't trust cheap products that much. So, I just keep the bottle standing and the valve never touches my drinks :)

Hope you make your own cap! Let me know if you do, and if you have any questions feel free to ask!


If you liked my instructable you're welcome to check out my instructables page for more :)

See you soon!

If you want to support me in making more projects, you can buy me a coffee!

Donations of any amount are appreciated, and 100% of your donations go to future projects!

Thanks to all the people who have already supported me!!

57 Comments

NirL 2 years ago

Hi,
Thanks a lot for the comment! Sorry for the late response, I just got the notification! Do hesitate to contact me if I don't answer :)

In any case, I didn't mention it in my text, but the valves I first used (those that came with rubber washers) we leaking. Eventually I found that the rubber washers are not necessary. I ordered a bunch from AliExpress and indeed some of them were pretty awful, so I added a link to the ones that worked best for me (well, it basically just worked! the others didn't).
Regarding the price - I think it says 0.01$ with a 'New User' discount, which I don't think you will actually get... AliExpress have good deals if you find the a good seller, but their advertising is the worst.

Thanks a lot for the kind words! :)
Nir

MTKapp27 2 years ago

I think it would be really cool to see you write up an instructable of the process you went through to make this. (~10 failed 3D prints) Include what your thought process was and what you learned.

NirL 2 years ago

Thanks for the comment! I always wonder what most people would prefer. Most often, people just want to see the end result, and in a sense I get why they feel that way. However, learning from other people's mistakes is much more insightful and seeing only the 'best' path taken to the final goal.
Anyway, there's a link to the 3D printed air valve I made (my best iteration I guess :) )


It's made of 3 parts - 2 stationary parts (larger objects) and one moving part. The moving part has room for a spring to be placed in it. I used a standard pen spring to make it accessible. It works pretty good, but not good enough. I leaked even with some grease on it.
Let me know what you think!

GTO3x2 2 years ago

I've made a similar cap, only it was just a bathroom sink stop valve with gasket material for sealing. This works, to a degree, but is not made to add air pressure, which may be much better. In my subsequent searching, I thought I found that air is not what needs to be done because it has to do with the partial pressure of CO2 gas in the system. I turn the bottle upside down and let that pressure dispense the drink, thus keeping the volume only CO2. It still eventually loses pressure, but it is somewhat better of retention of carbonation than normal bottle-opening. Dispensers have been made (and are currently sold) to connect a bottle to (upside down), flip a lever and dispense the drink. But they were cheap, leaked and/or didn't get popular.

You can see in my picture of my caps that the one bottle didn't work well, at all, this time around, LOL - had to actually squeeze the bottle to get the pop out. It's usually better, though.

richiebricker 2 years ago

Ive heard that simply squishing in the walls of the bottle works great because its doing the same thing, Not giving the CO2 room to form

GTO3x2 2 years ago

That can't be. All that pressure is lost during expansion, then pressurization. The indented bottle in the picture is like that out of neglect and an instance where it went flat.

NirL 2 years ago

Squishing the bottle might not work because the bubbles would expand the bottle back to its original shape. This might actually be worse than doing nothing. However, if you squish the bottle and make it stay that way (using a rope or something), it might work (essentially, you're making the bottle smaller).
So I think I'll have to agree with GTO3x2 on this :)
Thank you both for the input!

jdh2550 2 years ago

Nice simple idea - but what we need is a little science to really make this sing

What I want to know is how much PSI is needed to keep the fizz.

@NirL - do you know how many PSI it takes to stop the bubbles?

My ideal solution would be a valve I could simply blow into (for personal drinks only of course!!!). But could my 50 yr old lungs create the pressure (it's a pretty small volume though). Or I could lug around my Harbor Freight compressor (just kidding - I know you just use a hand pump). (p.s. thanks for the note in reply to @TinkerGuy about bubbles vs dissipation - that makes sense)

@paul15282h - sure, if you pump like crazy you could make the bottle explode. But, umm, surely the bottle is strong enough to hold the pressure because the drinks company put a pressurized liquid in it in the first place? Or is the structural integrity of a partially filled bottle the issue?

NirL 2 years ago

Thanks for the question :)
From what I found online, soda bottles come pressurized at about 40 PSI or higher. I wanted to attach a pressure gauge, but the one I have is not calibrated (see picture) :(

My guess is that you need less than 40 PSI to keep the bubbles from forming, but it's hard for me to tell. Also, my intuition says that using your breath won't work. An easy way to test this is to open a fresh soda bottle and trying to blow air in, I'm not sure you could fight the bubbles that easily. After all, even inflating balloons can be a struggle for our human lungs..

Regarding the safety issues - I would probably be more worried about the imperfection we inflicted on the bottle cap than the bottle itself. Once pressurized, the bottle itself feels the same force pushing outwards whether filled mostly with air or liquid. The force the bottle 'feels' (F) is pressure (P) times the area (A):
F = P * A
in the direction of the pressure gradient = outwards. try searching 'pressure' in wikipedia or any fluid dynamics textbook. If failure does happen, I'm not sure if you'd want to have liquid or gas inside, but that's a different story I guess...

Hope that answered some of your questions, let me know if it didn't :)

richiebricker 2 years ago

Fish are very sensitive to everything, especially temperature changes and dont forget they are very alergic to air

paul15282h 2 years ago

JDH2550,
Yes, to a certain extent. I am not an engineer but as I understand it the more volume of gas (vapor) the greater the potential energy. The liquid is not compressible, the gas is. Therefore the greater volume of gas the more violent a failure would be.
In my opinion one should do a structural integrity test using extreme caution. To verify the safe pressure. I believe someone used a soda bottle to make a air pressure rocket. That would give you the an idea of safe pressure.

Hank43 2 years ago

Did you try using a CO2 cartridge inflater? I wonder if that would restore some of the fizz.
Something like

richiebricker 2 years ago

CO2 guy is trying to ruin youre fizz by putting CO2 in it!!! lol :)

NirL 2 years ago

I did not try one of those :) To restore the fizz you'll have to put it into the drink itself (like soda-stream machines). I wasn't going for that, but a DIY version is a great idea! :)
Thanks for the comment!

paul15282h 2 years ago

This is very dangerous! Do not over pressurize the bottle! The cap may not be able to stand very much pressure. If the cap breaks it could cause injury.

Use caution! No more pressure than reasonable.

richiebricker 2 years ago

Yeah but a funny injury. And whos gonna clean up all that damn soda? Ah they probably got a hack for that too

NirL 2 years ago

Thanks for the comment paul! :) you're right, pumping too much could be dangerous! Standard caps are able to stand a few atmospheres but once you poke a hole in them they could become weaker.

jdh2550 2 years ago

but you've replaced that hole with food grad stainless steel...

ghostie222 2 years ago

I didn't read all 31 comments, so this may have been answered already. I'm embarrassed to ask this dumb question:
How do you know that the air going into the bottle from the bicycle pump is clean air? Could you innocently be putting contaminated air into the bottle (not food safe)?

Thanks for answering this question, as silly as it might be.
Mary Ann
P.S.: One thing worth mentioning is that you have a couple of typos. The one that really needs correcting is you have at the bottom of your script the word "sanding" and I think that you meant "standing"..."If you keep the bottle standing..."
No judgement, just an observation.
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