Pressure – As first glance, this part of the equation makes the most sense. Here’s what we know: The higher the gas pressure above the liquid in the bottle, the more gas will be pressed into the liquid. Makes sense. However, here’s the kicker. Once you open the bottle, the vast majority of the carbon dioxide molecules that were forced into the soda at the bottling plant come flying out. It’s that unmistakable sound of PSSSSST!
What about those gadgets called Fizz Keepers (you know, those pumps sold at the grocery store that supposedly re-pressurize the soda)? Do they work? When you pump the piston up and down, you’re pumping plain old air (mainly oxygen and nitrogen) into the bottle. However, scientists tell us that the escaping gas can be pushed back into the liquid only by forcing more molecules of that particular gas (in this case carbon dioxide) into the space above the liquid. In reality there isn’t one more molecule of carbon dioxide in the liquid after pumping the Fizz Keeper gadget than if you had simply screwed the cap on tight. You guessed it… the gadget is just a glorified soda bottle cap. Yes, it gives you that satisfying PSSSSST! sound, but that’s all it does. So, in terms of PRESSURE there’s not much that can be done.
Temperature – Let’s cut to the chase. The secret to keeping your soda alive with plenty of reusable fizz is to keep the soda cold… plain and simple. The higher the temperature, the less the carbon dioxide molecules will dissolve. (By the way, try letting the bottle of soda sit out in the sun before dropping in the breath mints and watch out!) It’s especially important to keep the bottle tightly sealed while it is out of the refrigerator since the higher temperature makes the gas want to leave the liquid. Pour yourself a glass of refreshing soda, cap the bottle, and put it right back in the refrigerator. Keep it cold… keep the fizz.
