Carbonation is a process where soda makers pressurize soda with carbon dioxide. That means they pump a whole lot of carbon dioxide into a container. This forces some of the carbon dioxide to dissolve into the soda. But, this solution is unstable – very little carbon dioxide can stay in solution, which is why if sodas are left out, they go flat. How to keep your 2-L bottle of soda from going flat is simple: when not in use, keep it capped tightly and in a cold place (refrigerator or cooler).
Some people think squeezing the bottle to reduce the volume of air in the bottle will prevent it from going flat. NOT TRUE! Look at it like this:
What To Do:
Get a 2-L bottle of soda.
Drink about half.
Squeeze the bottle so there is very little air space in the bottle.
Cap it off tight.
Leave it alone overnight.
Check it the next morning.
What you should see the next morning is that more “air space” has appeared. That air space is not due to a leak in the cap, but rather the carbon dioxide coming out of solution. By squeezing out the air, you have given the carbon dioxide more space in the bottle, so it is in fact MORE LIKELY to come out of solution than if you had just left the air in there.
In fact, the best thing you can do is add MORE AIR to the bottle by pressurizing it. Even just a bottle that has had some drunk from it, when reopened, will hiss as the increased pressure from the carbon dioxide coming out of solution increased the pressure inside the bottle. So, if you can pressurize the bottle with air, less carbon dioxide can come out of solution. There are several devices on the market that can help keep your soda carbonated by allowing you to pressurize the bottle, like the “Fizz Keeper.”