Over-carbonated beer can make for a messy situation. Avoid exploding bottles by getting to the source of the excess carbonation and making some quick changes to amend the problem and save your brew. In the case that the beer is not salvageable, identify the mistake and apply the lessons learned to your next batch of beer.
One of the first components of fixing over-carbonated beer is identifying what is causing the excess carbonation. Bottling beer before it is done fermenting, storing it in an area that is too warm and adding too much corn sugar at bottling are three key reasons for an over-carbonated brew. Use a hydrometer to check the specific gravity of beer to ensure that it is done fermenting before bottling, because an incomplete fermentation causes the greatest problem. Bottled beer should be stored in a room with a temperature around 50 to 60 degrees Fahrenheit to prevent over-carbonation. Carefully measure corn sugar before adding it to the beer at bottling to ensure the correct amount is used.
The refrigerator is the first line of defense in helping to deal with an over-carbonation problem. While it does not solve the problem, it does make it more manageable and prevents bottles from exploding most of the time. Refrigerate over-carbonated bottles for a few days and try them again to see if this helps with the problem.
If bottles are sealed using crown caps, there is a solution to rid the beer of some of its carbonation; however, this does not work with swing top bottles. Pry the cap of a bottle just slightly, using a bottle opener, until the sound of carbon dioxide escaping the bottle is audible. Once the sound of the gas escaping stops, use the capper to recap the bottle with the same cap. Chill the beer before serving.
If the beer is infected with bacteria, it will smell bad, have a sour flavor upon opening and be over-carbonated. Bacterial contamination is irreversible, but it can be avoided in the first place through good sanitation. Ensure that all equipment used in the beer-making process is properly sanitized by washing and sterilizing it before use to avoid bacterial contamination in the future.