Few things frustrate a homebrewer as much as over carbonation because a bottle-conditioned beer with too much carbon dioxide could be ruined by too much foam or even explode!
Beer becomes over-carbonated when there is too much priming sugar used during bottle conditioning, or the beer has not yet completely finished fermenting when it is bottled. Use a hydrometer to ensure that fermentation is complete and properly measure priming sugar to avoid over-carbonation.
Read on to find out more about the science of carbonation and the specific steps to get the best quality foam for your beer!
Why is my homebrew beer over carbonated?
Nothing is more frustrating than finishing a several-month homebrew project only to have a volcano of foam erupt from your bottle the moment you take the cap off.
Beer becomes over-carbonated due to overactive yeast. If there is too much priming sugar in a bottle, or if the beer is allowed to carbonate for too long, high carbonation levels can build inside the bottle.
If yeast is left in a warm, hospitable environment with enough sugar, they will keep converting sugar into ethanol and carbon dioxide indefinitely. The two ways you can stop this process are to restrict the available sugars or to refrigerate your beer (yeast enters hibernation at temperatures below 55°F).
To prevent over carbonation in future batches, you’ll want to make sure to measure your priming sugar properly and to make sure to halt the final fermentation within 2-3 weeks by refrigerating your beer under 55°F.
Depending on the severity of the problem, you can degas your current batch either by letting your beer chill in the freezer or by physically removing the carbon dioxide from the bottle.
While adjusting temperature is fairly straightforward, using the right amount of sugar can be a little tricky. Sometimes beer can still explode even after being left to carbonate for the right amount of time.
You can get excess carbon dioxide If too much priming sugar is added before bottling. You can also see over carbonation If the batch isn’t completely finished fermenting before bottling since leftover sugar can still be converted into carbon dioxide.
Is over-carbonated beer bad?
Over carbonation is not only frustrating and hazardous, but it can also negatively impact your final pour.
When you open or pour from an overpressurized bottle, the foam that spills out will be incredibly volatile, carrying a lot of your beer out within the first few seconds and leaving the rest of the bottle flat. Even if you manage to get most of the overflow into a glass, there’s just no way to get a good head of foam from an overpressurized bottle of beer.
Since foam decomposes exponentially, the high quantity of loose foam you get from the over-carbonated beer will break down very quickly and prevent the formation of the kind of thick, stable head you get from a long, slow pour of properly carbonated beer.
Apart from ruining your chances at pouring a thick head of foam, seeing half your bottle pour out onto the floor is both messy and frustrating. A bottle exploding from extreme pressure is outright dangerous.
For the sake of your safety, sanity, and satisfaction with your homebrew project, I’ve listed a few ways to salvage a batch of over-carbonated beer, and some tips on how to prevent it from happening in the future.
How to fix over carbonated homebrew beer bottles
Over carbonation is not only annoying and wasteful, but it can even be dangerous if one of your bottles breaks under pressure. Luckily there are a few tricks that can help salvage the rest of your batch, even if you lost half your first bottle as foam.
Because the problems of over carbonation come down to overpressurization, the only way to salvage over-carbonated beer is to find a way to reduce the pressure in the bottle in one of these ways:
- Allow the bottles to depressurize naturally over time
- Lower the temperature of the bottle
- Physically degas and reseal the bottle
The easiest option is to wait; beer bottles aren’t entirely airtight, so the highly pressurized environment will seek equilibrium with the pressure of the outside air over time. Unfortunately, this method can take quite a bit of time and will have variable results.
Another way to depressurize your bottles is to take advantage of physics. Gas particles move at higher speeds at higher temperatures, which in turn exerts more outward force, or pressure, on whatever container they are being stored in. That means that by lowering the temperature of our beer, we can lower the bottle’s pressure.
In addition, carbon dioxide has been shown to be more soluble in water at lower temperatures, leaving less gaseous carbon dioxide to pressurize the bottle. So if we lower the temperature of our beer bottles by letting them chill in the freezer, even though the amount of carbon dioxide remains the same, we can potentially decrease the pressure enough to get a gentle pour from a previously overpressurized bottle.
If your bottles are so over-carbonated that neither of the above fixes work, you can always physically degas your bottles. To do this, you’ll need a long bottle opener with a lot of leverage, like this one. You’ll want to put just enough pressure on your bottle cap that you can hear slight hissing from the gas escaping the seal. You shouldn’t see any bend in the bottle cap if you do it right, and no liquid will escape. When you’ve let some of the gas escape, you can reseal your bottle with your bottle capper.
Unfortunately, all of these fixes will require a little bit of trial and error, depending on the level of carbonation in your bottles. In the end, the best way to solve over carbonation is to prevent it from the beginning.
How to prevent over-carbonated bottled homebrew beer
We know that over carbonation results from too much sugar available for the yeast in your beer to convert into ethanol and carbon dioxide.
To prevent over carbonation in the future, we want to be very careful about the amount of sugar available after bottling, whether that sugar is leftover sugar from fermentation or priming sugar. It’s also important to remain aware of how much time the yeast is left to carbonate the beer.
With some practice and experience properly measuring the three factors involved in carbonation (sugar, yeast, and time), you will be able to ensure perfectly carbonated bottles every time.
How to know when fermentation is finished
While it’s easy to get excited about new homebrew, it’s important not to skip ahead to bottling before fermentation is complete.
If beer is bottled too soon, the excess sugar will continue to ferment in the bottle and completely change the recipe. All of the carbon dioxide that was supposed to be expelled through an airlock during the last fermentation stage will build up inside the bottle and almost always result in over carbonation.
You’ll want to be careful even if you see fermentation slow down. Because yeast breaks down different sugars at different rates, your sucrose will be completely fermented before your malt extract.
Luckily, there are some pretty straightforward ways to tell if fermentation is done:
- Use a hydrometer to measure your beer’s gravity – This method will require some planning since you will need to take measurements before and after fermentation, but it is by far the most accurate way to keep track of the fermentation process. Final gravity readings will be included in your recipe, so using a hydrometer will vastly improve the accuracy and consistency of your brews.
- Observe the physical changes – If you don’t have a hydrometer or forget to take an initial reading, you can always look for signs that your yeast have finished converting sugar to carbon dioxide.
For a complete breakdown on these methods and on how to use a hydrometer, you can read my in-depth discussion here.
How to properly measure priming sugar when bottling
While measuring ingredients seems like a pretty straightforward process, there are some best practices to keep in mind.
When following a recipe, it’s important to measure your ingredients by weight, not volume. That means when given a choice, you should always take out your scale instead of your measuring cups.
When you measure by weight, you account for any differences in the sugar’s processing method and maintain precise accuracy even when you scale up your recipe. That’s why professional breweries and bakeries prefer to measure by weight.
If you don’t have a recipe, or if your recipe only provides a volumetric priming sugar measurement, you can always use a calculator like this one by Northern Brewer to get the exact amount of sugar needed for various priming sugars and styles of beer.
How to know when your beer is properly carbonated
If you followed the best practices above and followed your recipe to the letter, telling when your beer is properly carbonated should be a simple matter. You can go ahead and follow your recipe’s recommendation for the time needed to produce proper carbonation, usually 2-3 weeks.
Here are few ways to track carbonation levels:
- Sediment – Because carbonation is basically another short round of fermentation, you can keep an eye out for sediment building up at the bottom of your bottles to clue you in to the yeast’s progress.
- Carbonation – You can also try turning a bottle over to look for small carbonation bubbles rising up the side of the glass.
- The raisin trick – If you’re nervous about sugar levels and you want a really obvious sign that it’s time to fridge your beer before they over carbonate, you can even put a raisin in one of your bottles; once the bottle carbonates, the raisin will rise to the top.
In the end, beer brewing is all about accuracy, so as long as you follow the recipe and the recommendations above, you should never have to worry about over-carbonated beer again!
Check out the web story version of this article here!