If the airlock is not bubbling, it may be due to a poor seal between the lid and the bucket or leaks around the grommet. Fermentation may be taking place but the CO2 is not coming out through the airlock. This can also be caused by adding too much water to the airlock.
Within 24-36 hours, carbon dioxide normally starts bubbling through the airlock, as long as everything is working correctly and if the fermenter is sealed properly. Fermentation can take as little as 3 days if you are using a fast-acting yeast and the temperature is ideal.
Most probably the yeast is simply taking longer to get the job done or, less likely, wild yeast and bacteria have taken residence. Most likely it is the strain of yeast that is simply taking a little longer than usual. If in doubt have a sniff in the fermenter.
The short answer: Although most ales ferment in 2-5 days, I always recommend you wait at least 2 weeks before moving to bottles/kegs for the best results. Lagers on the other hand ferment in 2-3 weeks followed by several weeks or even months to condition.
It's not bubbling!
If an airlock fails to bubble, all it means is that the pressure within the fermentor isn't high enough to make it do so.
If the airlock is not bubbling, it may be due to a poor seal between the lid and the bucket or leaks around the grommet. Fermentation may be taking place but the CO2 is not coming out through the airlock. This can also be caused by adding too much water to the airlock.
After pitching yeast, simply check on the mash every 12 hours or so to make sure that sometime during the first 12-48 hours after yeast is added there is movement in the airlock (the airlock should bubble a at least few times a minute).
The primary reason for fermentation to not start is the health of the yeast, or too little healthy yeast, and this is usually the cause. Perhaps the packet or vial of yeast was old and there was little healthy yeast left to do the job.
Beer, we always recommend that you bottle your beer no later than 24 days in the fermenter. You can go longer but the longer your beer sits the more chance you have to get an infection and get off-flavors in your beer.
The duration of a secondary fermentation or conditioning phase can vary from as little as a week to over 6 months. Actual time will vary and you should let your taste buds and nose determine when a beer is ready for bottling. During extended secondaries, you should make sure your airlock does not dry out.
Heat things up. Warming up the carboy is probably the most reliable way to restart a stalled fermentation. Some yeast strains are more temperature sensitive than others and may require some warmth to complete the job.
The yeast need this oxygen to grow and to produce important cell wall constituents. It is important to introduce enough oxygen into wort at the beginning of fermentation. Shaking the fermenter will, at best, add about half the recommended level of 10 parts per million oxygen into solution.
You can catch a stalling fermentation within the first 24 hours by noticing that your pH levels aren't falling rapidly. Because beer doesn't ferment at a constant rate, after this one-day window you shouldn't worry until the gravity reading has stagnated for at least 48-to-72 hours.
How Do I Know if My Fermentation Airlock Is Working? Once your bacteria and yeast are going to town on those sugars, you should start to see the CO2 bubbles moving through the fermentation airlock. The more active the bacteria and yeast are, the more bubbles they will make.
Will an airlock clear itself. Even if you run out of water, air should automatically clear in a well-constructed low-pressure water pipe system. The air should naturally climb to the top and discharge as the pipe system fills up.
Low water pressure can happen for a variety of reasons. Airlocks are often overlooked yet can be one of the simplest issues to rectify. An airlock in the pipes will eventually result in no water at all if it isn't taken care of. Even worse, it can cause blockages, overflows and other serious problems.
The short answer is that, on average, it takes about four hours to brew beer, one to two weeks to ferment and condition, two hours to package in bottles, and one to two weeks to naturally carbonate in bottles.
In short, if all of the sugars have been consumed, the answer is yes. The longer the fermentation process takes, the more sugar is converted into alcohol. As more sugar is converted, the resulting beer will feature a higher alcohol content.
Oxidization usually tastes stale or old or like wet cardboard or paper. Oxidation occurs mostly when an excessive amount of oxygen is introduced to the wort when it's still very warm or after fermentation is complete during bottling or kegging.
So let's talk about what fermentation looks like. During fermentation you will get foamy bubbles on the top of your beer, this is called krausen and is perfectly normal for brewing. Depending on the batch that you are brewing you may get a very high krausen or a low krausen.
Fermentation times can be shortened by using powdery (non-flocculent) strains of yeast or by mechanically stirring the fermenting wort. The yeast can also be roused toward the end of fermentation by the injection of carbon dioxide or by using a re-circulating device.
A secondary fermentation is done by moving your beer to a another fermenter towards the end of fermentation. This could be anywhere from the 3rd to 7th day. Ideally, leave your beer in secondary fermentation for at least one week, but feel free to add more time if additional ingredients are added for flavor.
Worst that will happen is that as the brew puts pressure in the airlock, the excess water will be pushed out the holes in the lid.
Trying an Open Fermentation
As soon as you notice fermentation starting to slow down rack into a carboy and put the airlock in place. Your fermenter should only be open during “primary” fermentation which is when the first 70% or so of your sugars are fermented (here's more on Primary vs Secondary Fermentation).
In reality, the fact that the bubbling stopped is only an indication that the fermentation may be done, but is is not an absolute indicator. It does not necessarily mean that all the sugars are gone from the wine must, and it definitely doesn't mean that the fermentation can't start up again.