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I am looking for some trick or gazzette to keep a bigger bottle of coke longer so that it doesn't lose all the fizz everytime it's opened again! Something which could keep the CO2 longer so that a bigger bottle could be used longer? Anything we have?

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You can get a little pump that attaches to the top of the bottle.

https://www.amazon.co.uk/Jokari-Fizz-Keeper-Pump-2-Litre-Bottles/dp/B00004XSH3

Fizz-Keeper Pump Cap

It pumps in air to pressurize the bottle, thus preventing the carbon that makes the drink fizzy from escaping the liquid.

  • I have one of these, the whole point is that it pumps air out creating a vacuum – bigbadmouse Mar 28 '18 at 11:42
  • Must be different to that one. Those pump air in. If they pumped it out the plastic bottle would be crushed. – aaa Mar 28 '18 at 13:32
  • it would depend how far you pumped it - the liquid stops the bottle crushing in on itself – bigbadmouse Mar 28 '18 at 13:40
  • Consider when the bottle is only 10% full and you pump all the air out. – aaa Mar 28 '18 at 13:41
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    @bigbadmouse You are mistaken. There is no vacuum created. This pumps air into the container to conserve the high pressure to keep the CO2 in solution. The pressure is greater than the ambient. The containers are designed to be under pressure. You may be mistaking vacuum pumps for wine bottles which can withstand negative pressure without collapsing. Further, still wine must not pressurized. Sparkling wine is stored under pressure; (more pressure than this plastic pump can generate or hold) so try to re-cork it if you can to conserve it. Better; finish the whole bottle with friends. – Stan Mar 28 '18 at 18:18
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Something that will help a little is to get it very cold before it's opened, and don't let it warm up. Don't even let it warm up after you reclose it, as it will reach equilibrium faster when warm. I'm tempted to say it's because carbon dioxide is more soluble in cold water, but the physics of carbonation is much more complicated than simple solubility.¹ And while I don't know much about the underlying physics, the gas will escape faster if it is warm (and build up more pressure, assuming the container is closed).

Also, let it sit very still for some hours or days before it's opened. When you jostle or shake it, not only are nucleation sites introduced, but the (not quite) bonds between the carbon dioxide and the water are disturbed, and the solution is less able to bear the supersaturation until its former state is re-established.

If you want to cheat, you can buy a CO₂ canister from a welding supply store and make a lid with a nozzle glued into it. Top up the CO₂ by getting the soda nice and cold then pumping in some gas, keeping the pressure low so the plastic doesn't burst. When the pressure drops as the gas is absorbed, pump in some more. When the pressure is low enough, remove the nozzle and put a normal cap on. If you're really enterprising, you can produce CO₂ in a separate chamber with acid and baking soda.Regulating pressure will be a challenge.

1: Some brief further explanation here: https://winemakermag.com/1308-inert-gases-techniques

  • Paragraph 1 describes stasis or equilibrium. Paragraph 2 is mis-leading as there are no bonds formed by dissolving the gas into the liquid. Paragraph 3 describes 'SodaStream' which can also be used to "cheat" fizzlessness. Fizzlessness (?) – Stan Mar 28 '18 at 18:27
  • @Stan I don't fully understand the physics of stable supersaturated gases in liquid. If you do, please explain or link to a resource so I can improve my answer. If not, I humbly remind you that fizzy soda exhibits hysteresis, and that obviously isn't explained by temperature or pressure. – piojo Mar 29 '18 at 1:51
  • @Stan Also, using a carbon dioxide canister is in no way equivalent to pumping in air. The former will strongly increase the partial pressure of carbon dioxide, the later barely will. – piojo Mar 29 '18 at 1:58
  • I was referring to Henry's law. The Coke has two states in this question; one is under pressure and one is reduced, all other factors not withstanding. In either case, a stasis will be achieved. The desirable one is with CO2 in the Coke. The other is flat Coke. – Stan Mar 29 '18 at 2:03
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    YES. SodaStream uses compressed CO2, not air. The net result is that CO2 content in the Coke is increased over any other common household solution. – Stan Mar 29 '18 at 2:05
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Colas go "flat" because of loss of CO2. The only way to keep the CO2 in solution is to prevent it from getting out. While the bottle is sealed, the liquid reaches an equilibrium where the partial pressure of CO2 outside the liquid (but still inside the bottle - the little "air" space at the top) is equal to the partial pressure of CO2 inside the liquid.

As soon as the bottle is opened, the partial pressure of CO2 in the "air" space drops and you see CO2 effervescing from the liquid. This is the liquid's attempt to reach equilibrium again. While the cap is off, equilibrium will not be reached until the CO2 in the liquid is equal to that of ambient air (about 0.04% - aka "flat"). Putting the lid back on helps limit this process, but will NOT prevent the liquid from losing its "fizz". The liquid will reach another equilibrium point after some time at which, the concentration of CO2 in the liquid has dropped in order to stabilize the concentration of CO2 in the air space.

The pressurization gadget mentioned at the very top of the responses does NOT work at all as it does next to nothing to add CO2 to the air space. Ambient air is about 0.04% CO2. You will not be able to pressurize the bottle with enough air to prevent the release of CO2 from the liquid. Not possible.

The only way to prevent the liquid form going "flat" is to introduce CO2 at the same rate at which it leaves. This means you need a system that injects CO2 into the bottle as the liquid is poured out. I'm not aware of anything that does this at the moment.

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If you buy your soda in a big plastic bottle, I recommend squeezing out as much air as you can before you screw the cap back on. My theory is that the carbonation wants to leave the soda, but if there is nowhere for it to go (no big pocket of air in the bottle), then the carbonation will stay in the soda.

(I'll determine whether my theory is right by the number of thumbs up and thumbs down I get on this answer.)

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    I'm up-voting you back to zero as I see no difference at all between your method and the air removal pump method - except yours is cheaper. – bigbadmouse Mar 28 '18 at 11:41
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    I think this is counterproductive, because carbon dioxide is kept in solution at an equilibrium based on pressure. If you squeeze out the air in the bottle, the soda will lose more carbon dioxide before pressure begins to build and equilibrium is reached. – piojo Mar 28 '18 at 15:35
  • Sorry Brett, but piojo is correct. Squeezing the air out is worse than simply recapping the partially-filled bottle for the reason piojo gives. – Stan Mar 28 '18 at 18:21
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    @Stan Makes sense, now that I think about it. Thanks. – BrettFromLA Mar 29 '18 at 1:16
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Its a bit more involved, but you can get a carbonator cap. We use it in homebrewing to carbonate beer and to keep it carbed. It allows you to hook up a co2 tank to a 2 liter bottle. You would need the cap, a regulator and a co2 tank or cartridges.

cap: https://www.homebrewing.org/CarbaCap_p_108.html co2 regulator: https://www.morebeer.com/products/co2-injector-ball-lock.html

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A bottle of soda will lose it's fizz if it is opened when warm,so when you decide to open a large bottle,the first thing to do is to refrigerate it. When the bottle is cold, you can open it and pour the soda. Don't let it get warm after you open it. Pour the soda, re-cap it,then put the entire bottle back in refrigerator. From then on,the way to pour servings of soda will be:

  • take bottle from refrigerator
  • pour soda
  • re-cap bottle
  • put bottle in refrigerator
  • This is essentially piojo's answer in point form. – Stan Apr 3 '18 at 13:15
  • I'm all for explaining the chemistry behind things,but this exchange is Lifehacks and not Chemistry. I don't think a chemical explanation is supposed to be here. – user23758 Apr 3 '18 at 18:17
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We all know that for each time it's opened some fizz escapes. Reducing the number of times it is opened (or handled) therefore reduces the amount of fizz escaping.

One way for a larger bottle to retain fizz can therefore be to divide the contents into several smaller bottles, so as to reduce the number of openings before actually being consumed.

Note that this should be done with the beverage being as cold as possible to reduce loss of fizz when pouring to the other container(s).

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Keep the bottle cold and in an upright position. If you drink the coke within a day or two, it will keep fresh and sparkling, and you should hardly notice the difference.

Tip: The more coke there is inside the bottle (and the less air), the less CO2 will escape from the coke and into the (closed) bottle while it is stored in the fridge (results from Henry's law). Pour over coke from a half-full bottle over to a smaller container (or into another half-full bottle of coke, to fill one single bottle), and you will save space and loose less sparkling gas.

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Some theory

CO2 "evaporation" is a result of the gas trying to reach an equilibrium between what is solved in the liquid (coke) and what is in the air above (Henry's law).

Keep in mind:
  1. Less CO2 escapes if the temperature is kept low (CO2 is more 'soluble' in low temperature, and less will escape from the liquid)
  2. Less CO2 escapes if the bottle is kept upright (smaller surface area than when the bottle is laid down, so this will slow down the 'evaporation' process)
  3. Less CO2 escapes if the bottle is almost full (smaller 'air' volume to fill with CO2 escaping from the liquid)
Also remember:

The moment you have opened a bottle of coke, then non-sterile air from the surroundings mixes with the content inside the bottle. An opened container will only keep fresh (without growth of bacteria or fungus) for a limited number of time (a week or two).

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