Product: Food Dispenser
Re-Pop   (+3)  [vote for, against]
the real way to preserve carbonation

Buying 2-liter bottles of soda is so disappointing. After the first 1/2 it starts to go flat and lose any character it might have had, or tacit approval because it had bubbles. The local supermarket didn't have any 12-packs of 12-oz cans; only 8-packs of 10-oz cans at 80% of the 12-pack price. 80 oz for $6.99 against 144 oz for $8.98. So I reluctantly bought the 2-liter bottle for $2.69, 67.23 oz. But I hate it when it goes flat. What to do?

If you use the current tech of pumping up the pressure you will delude yourself, as I did, into thinking you are maintaining the carbonation in the fluid. The CO2 will try to equalize anyway and leave the fluid despite any increase in pressure over it. Any preservation of the bubbles is minuscule, if at all. The only way to preserve the carbonation is to reduce the volume of the vessel, whether you pressurize it or not.

This handy unit is a screw-on cap with a pump like the ones that don't work, but this pump inflates a bladder that fills the space in the bottle over the liquid. Whatever carbonation is left in the soda will not have space to move into. With a flip lid for pouring that releases any pressure before soda flows, the user sets the bottle upright again and pumps up the bladder, replacing any additional space created by the portion taken.
-- minoradjustments, Aug 04 2023

Goon Bag
[a1, Aug 04 2023]

Designed for carbonated beverages [a1, Aug 04 2023]

Do you know what these are used for?
Sure, you put them into soda bottles to keep the fizz! [a1, Aug 05 2023]

Inflatable bladders are one of the methods for trying to keep a half empty glass bottle of wine from going off. Though those systems are designed merely to remove air, not to increase pressure as well
-- pocmloc, Aug 04 2023

My 2 minute Google degree tells me that the CO2 wants to equalize equivalent volume with the atmosphere. So you don't just need higher pressure, but CO2 pressure. Get a pump which uses CO2 cartridges to pressurize.
-- Voice, Aug 04 2023

Alternately, a box & bag arrangement as used for bad wine (link: goon bag). To handle carbonation pressure the bag might need to be a bit more robust, but it's a proven method for dispensing liquids while excluding air from the container.
-- a1, Aug 04 2023

// To handle carbonation pressure the bag might need to be a bit more robust //

And of course, after I thought that - I find someone else thought it before I did. (link: Nova-bib).
-- a1, Aug 04 2023

I've used the hand vacuum pump and soft rubber reed-valve plugs to preserve wine in glass bottles. That works great, but I've never been able to enjoy the last half of even a quart bottle of carbonated beverage.

As distinct from the Goon Bag, that just has to go flaccid in order to succeed, and the Nova-bib, which I don't understand how it keeps its carbonation except by re-carbonating the remainder and is so-o-o-o complicated, the Re-pop is a cap with a hand pump that screws onto the neck of any soda bottle. Crack a 2-liter bottle of Coke. Pour what you want, and then screw the Re-Pop on instead of the original cap. Turn the head of the cap and a shaft rises from the middle of the cap. This is the hand pump. Pump away, inflating the bladder built into the base of the Re-Pop until the volume over the remainder is sufficiently reduced, much the same way there's always a bit of space over an unopened bottle's contents. You could integrate a little circular pass/fail pressure gauge into the cap to let you know you've reached to optimum pressure. [You don't need to add any CO2, you just need to reduce the space it can expand into.]

How many of us have filled condoms with mundane fluids and enjoyed the ensuing hilarity? Materials will not be problem. A quick rinse and the Re-Pop is ready to nuzzle its next nozzle.
-- minoradjustments, Aug 05 2023

I think you’re just not drinking enough. Open it, drink it all. Problem solved.

I didn’t look closely at the Nova-Bib design, I only found if by looking to see if anyone had adapted the bag in a box idea to carbonated beverages. Theirs might be too complicated, as you say. I’m thinking it should be simple as long as the spout prevents air from entering the bag. Spout at the lowest point, original “charge” of CO2 at the highest, shouldn’t that be enough?

And as an aside - If hilarity ensues when YOU fill a condom, you’re probably doing it wrong.
-- a1, Aug 05 2023

//How many of us have filled condoms with mundane fluids and enjoyed the ensuing hilarity?//

First off; [marked-for-tagline],
Second off mmmm'no. Only one fluid.

Ah say, ah say, you're using them all wrong boy. Gotta get you're head in the game.
-- 2 fries shy of a happy meal, Aug 05 2023

// Spout at the lowest point, original “charge” of CO2 at the highest, shouldn’t that be enough?//

I see what you're saying. If you let the bag shrink as the fluid is dispensed the CO2 has nowhere to expand up into. It sounds right but I don't know if the gas/fluid thing works that way. Will the volume of the bag remain the same as the carbonated fluid left in it as it is dispensed? The only ways to keep carbonation are 1) replace served fluid with charges of CO2 from an outside source with a smart valve (probably what the Nova does.), or more simply 2) reduce the volume over the fluid in the container as it's used, whether it's rigid or a bag. There are a few ways to do that, either with a sliding piston in a specialized container, rolling down the top of the bag like a toothpaste tube under pressure, etc. I chose the pump and bladder for portability, ease of use, and the condom thing.
-- minoradjustments, Aug 05 2023

But as the bag is drained its volume decreases regardless. No piston or squeezy thing necessary.
-- a1, Aug 05 2023

random, halfbakery