Beer Info FAQ

Why Do Carbonated Drinks Go Flat When Left Open?

Carbonated drinks, also known as fizzy drinks, are beloved for their refreshing and bubbly nature. However, if you've ever left a carbonated drink open for too long, you may have noticed that it loses its fizz and becomes flat. But why does this happen? In this article, we will explore the science behind why carbonated drinks go flat when left open and provide tips on how to prevent this from happening.

The Carbonation Process

To understand why carbonated drinks go flat, it's essential to grasp the carbonation process. Carbonation is the process of dissolving carbon dioxide gas (CO2) into a liquid, creating those delightful bubbles. When a carbonated drink is manufactured, it undergoes a process where carbon dioxide is infused into the liquid under pressure. This process allows the CO2 to dissolve and remain in the liquid until the container is opened.

Loss of Carbonation

When a carbonated drink is exposed to the air by opening the container, several factors contribute to the loss of carbonation:

  1. Escape of Carbon Dioxide: The most significant factor is the escape of carbon dioxide gas from the liquid. When the container is opened, the pressure inside decreases, causing the dissolved CO2 to escape in the form of gas bubbles. As more CO2 escapes, the drink loses its fizziness.

  2. Equilibrium Restoration: Carbon dioxide naturally seeks equilibrium between the liquid and gas phases. When a carbonated drink is opened, the CO2 in the liquid tries to restore equilibrium by escaping into the air. This process continues until the concentration of CO2 in the liquid and the surrounding air reaches equilibrium, resulting in a loss of carbonation.

  3. Temperature Effects: Temperature plays a role in the rate of carbonation loss. Warmer temperatures accelerate the escape of CO2, causing the drink to go flat more quickly. Conversely, colder temperatures can slow down the loss of carbonation, allowing the drink to retain its fizz for a longer time.

Preventing Flat Drinks

While it's inevitable that carbonated drinks will eventually go flat once opened, there are a few steps you can take to prolong their fizziness:

  1. Refrigeration: Storing carbonated drinks in the refrigerator can help slow down the loss of carbonation. The colder temperature reduces the rate at which CO2 escapes, allowing the drink to maintain its fizz for a longer period.

  2. Sealing the Container: After opening a carbonated drink, make sure to seal the container tightly. This helps minimize the contact between the liquid and air, reducing the rate of carbonation loss.

  3. Using Carbonation Caps: Carbonation caps are special caps that can be used to reseal carbonated drink bottles. These caps allow you to restore some of the lost carbonation by injecting CO2 back into the bottle. While this method may not fully restore the original fizziness, it can help extend the life of the carbonation.


In conclusion, carbonated drinks go flat when left open due to the escape of carbon dioxide gas, the restoration of equilibrium, and the effects of temperature. While it's impossible to prevent carbonated drinks from eventually losing their fizz, storing them in the refrigerator, sealing the container tightly, and using carbonation caps can help prolong their carbonation and keep them fizzy for a longer time.

Frequently Asked Questions

Q: Can shaking a carbonated drink make it go flat faster? A: Yes, shaking a carbonated drink can accelerate the loss of carbonation. The agitation causes the CO2 bubbles to expand and escape more quickly.

Q: Does the type of container affect the rate of carbonation loss? A: Yes, the type of container can impact the rate of carbonation loss. Plastic bottles are more permeable to gases, allowing CO2 to escape more easily compared to glass bottles or cans.

Q: Can I restore the fizziness of a flat carbonated drink? A: While you cannot fully restore the original fizziness of a flat carbonated drink, using carbonation caps can help inject some CO2 back into the liquid and extend its carbonation life.

Q: How long does it take for a carbonated drink to go flat once opened? A: The rate at which a carbonated drink goes flat can vary depending on factors such as temperature, container type, and the amount of carbonation initially present. On average, it may take a few hours to a couple of days for a carbonated drink to go flat once opened.

Q: Can I use a vacuum sealer to preserve the carbonation of a carbonated drink? A: Vacuum sealers are not recommended for preserving the carbonation of carbonated drinks. The pressure created by the vacuum sealer can cause the liquid to foam and potentially lead to an explosion when opened.

Q: Are there any additives or techniques to help retain carbonation in homemade carbonated drinks? A: Yes, there are additives and techniques that can help retain carbonation in homemade carbonated drinks. These include using priming sugar during the brewing process, proper bottling techniques, and ensuring a tight seal on the bottles.

Remember, while carbonated drinks may lose their fizz over time, they can still be enjoyed even when flat. So, sit back, relax, and savor the flavors, regardless of the carbonation level!