Bottle conditioning is the process of carbonating beer in a bottle. Sugar is added to finished beer then siphoned into bottles. Residual yeast cells consume the sugar and produce carbonation. The carbonation then dissolves and carbonates the beer. Most beers can be carbonated and conditioned in about 2 weeks.
Judging fermentation completion
First, the beer must be finished with fermentation. This is best done by both letting the beer sit in primary for at least 2 weeks, and checking the final gravity.
If the final gravity matches what the recipe estimates it should be, fermentation is complete. If you are not sure, the best method is to check and record the final gravity, wait a couple days, then re-check the final gravity. If the gravity has dropped, fermentation is still taking place, and the beer should be allowed to finish. If the gravity is stable, fermentation has completed and the beer can be bottled.
Never rely solely on how the beer or airlock looks to judge fermentation completion. Sometimes, temperature or pressure changes may force dissolved CO2 out of suspension and out the airlock, making it seem as if the beer is still fermenting. Always check the gravity of the beer with a hydrometer before packaging the beer.
All equipment that will touch the beer much be sanitized. This includes: bottling bucket, racking cane and tubing, bottles and caps, a spoon, and a thief for taking a sample of the beer to check the final gravity.
First, a priming solution is made by boiling corn sugar in 1 cup clean water (refer to your recipe for the amount of corn sugar needed). Priming sugar is simply any sugar use to prime, or carbonate, beer. The best sugar to use is corn sugar, as it is the easiest for yeast to digest and is readily available. Boiling will make sure the solution is sanitized, and only a minute or two is needed. The solution is cooled, then poured into the bottling bucket.
The beer is then racked into the bottling bucket. Rack slowly and carefully here; you want to avoid oxygen contact as much as possible. This is most easily done by putting the end of the siphon tubing under the level of priming solution. This will allow beer to siphon directly into the priming solution, as well as help the solution mix evenly into solution. Additionally, gently stirring the beer with a spoon will help even distribution. This is important; if the solution is not evenly dissolved into the beer, you may end up with uneven levels of carbonation in the bottles.
When starting the siphon, avoid the sediment (or trub) on the bottom of the fermenter. Transfer only the clear beer over. It is best to start the bottom of the racking cane at least 6 or so inches from the bottom of the fermenter. As the level of the beer lowers, carefully lower the bottom of the racking cane, leaving the settled trub behind.
Once the beer is in the bottling bucket, open the spigot to fill each bottle. Slant the bottle slightly sideways, so beer slowly falls down the sides of the bottle; this will help minimize splashing. If using a bottling wand, simply press down on the bottom of the bottle with the filler to fill the bottles. Cap the bottles as you go with a bottle capper .
As mentioned in the Carbonation, Conditioning, and Aging section, different beer styles are best with different levels of carbonation. This is most easily attained at bottling by changing the amount of added priming sugar. The amount of sugar used has a direct relation on the final carbonation level. More sugar leads to more fermentation, causing more carbonation in the finished beer. If building a recipe using a recipe calculator, refer to the amount specified by the calculator. Otherwise, charts exist on the web, or a rule of thumb (4-5 ounces, or ¾ cup) can be used.
After the bottles are filled and capped, store them at room temperature and away from light for 2 weeks. During this time, yeast will consume the priming solution, producing carbon dioxide, and carbonating and conditioning the beer. After 2 weeks, the bottles can be stored in the refrigerator. The refrigerator will cool the beers down as well as help CO2 dissolve evenly throughout the bottle.
Is it carbonated?
There are a couple things to look for when serving homebrew to judge carbonation and conditioning. First, during the 2-week carbonation/conditioning phase, a small layer of sediment should build up in the bottles. This sediment is composed of yeast cells, and is a good first indicator that carbonation is occurring.
You should hear the bottle pop slightly when opening the beer, and you may see some small wisps of CO2. If you hear a loud pop, and perhaps foam coming out of the bottle, conditioning may not be complete. Let the beer sit for an extra few days, both at room temperature and in the refrigerator.
When pouring the beer into a glass, pour carefully. Let the clear beer flow into the glass leaving the sediment behind in the bottle. Go slow; it’s best to start with the glass tilted when doing most of the pour. Towards the end, tilt the glass upright; this will allow a good head to form. This is called a “homebrew pour”, and may take some time to perfect.
In the glass, look for a good, thick head with small bubbles that lingers; this is a good sign of a well-conditioned beer. Large bubbles that dissipate quickly is usually a sign that the beer may not be finished conditioning. As you drink the beer, pay attention to overall flavor, body and smoothness. If these don’t seem quite right, the beer may need to condition longer.
Over- and under-carbonation
Over-carbonated beer is easy to notice. The bottle, when opened, will pop loudly, and will begin to foam. Be careful if you encounter this, as the foam can cause a big mess. When poured, the beer will have a lot of foam that dissipates very quickly. The beer will taste very sharp and acidic as well. This is caused by the large amount of carbonic acid (CO2 dissolved in the beer).
If you notice your beers becoming increasingly carbonated over a period of a couple weeks or longer, you may have a bottle infection (usually called a “gusher infection”). This is caused by a contamination during bottling, and the beer will get worse over time. You should seriously consider dumping the beer if this is the case, as bottle bombs are a serious health hazard. When dumping this beer, put the bottles carefully in a Tupperware tote, cover them with thick blankets, wear heavy gloves, and carefully open each bottle to relieve pressure.
Luckily, following proper sanitizing and bottling procedures, gusher infections are exceedingly rare.
Under-carbonated beer is likewise easy to notice. The bottle will not pop loudly when opened, the pour will likely have a thin head that dissipates quickly, and the beer will feel thick on the palate. If the beer is still young, you may want to give the beer more carbonating time. If the beer does not carbonate, and has been sitting for at least a month with zero signs of improving, you may consider attempting to re-carbonate the beer. Re-carbonating is done by opening each bottle, and adding a small amount of yeast and some sugar. Here, the best option for sugar will be carbonation drops, which are small sugar pills made for adding to bottles.