There are various schools of thought about the best time to bottle home brew. It may be later than you think.
Generally speaking, one of the best (and easiest) things you can do to improve your home brew is leave it in the fermenter for a couple of weeks before bottling.
Doing this will give you a much tastier beer because of the extra time the yeast has to ferment the beer properly. This applies to all brewing methods, whether kit, extract or all grain.
Primary and Secondary Fermentation
During fermentation yeast convert sugars in the wort into alcohol and carbon dioxide. They also produce a number of other by-products which affect the taste of the beer.
Depending on the beer style these are more or less desirable.
A lot of ales, for instance, derive much of their character from the fruity sub-tastes produced during the beer making process.
Lagers or lighter ales, on the other hand, rely on a purity of finish as a hallmark of their style.
Yeast in Action
If you have an airlock fitted to your fermenter you’ll be able to observe the action of the yeast soon after you seal in your beer.
Bubbles of air will frantically escape through the bubbler, usually within twenty four hours. The activity will gradually die down to one or two blurps a minute, and after three days or so you probably won’t be aware of any yeast action.
Don’t jump to conclusions though – that doesn’t mean that nothing’s going on.
A bubbling airlock is not the only sign of fermentation.
Once the yeast have worked their way through the sugars, processing all of the fermentable ones and leaving behind the non-fermentables which give the sweet malty taste to beer, they move onto their second course.
Slowly they reprocess some of the fermentation by-products, starting the stage of brewing known as secondary fermentation.
Given enough time, yeast will clean your beer thoroughly and you’ll bottle with the best chance of a decent batch.
As a general rule of thumb around two weeks from brew day should be fine, but bear in mind that heavier, stronger beers usually require longer.
Dangers of Rapid Bottling
Other than the benefits outlined above, there is another good reason for leaving your brew in the fermenter.
Assuming that they are otherwise healthy, yeast will continue to process fermentable sugars until they are gone, releasing carbon dioxide gas as they go.
Although the airlock may have stopped bubbling, the process could still be happening inside at a much slower rate.
Gas isn’t accumulating in enough quanitities to escape in a noticable way, but it’s still being generated. If you bottle before the yeast can finish, fermentation of the remaining sugars will continue inside the bottle.
If enough sugars are left in the brew the gas given out can be substantial, enough to explode your bottles. So be careful.
Checking if Fermentation is Complete
If you want to bottle as soon as possible and let the secondary fermentation take place in the bottle, there is a way to check that the risks of exploding bottles are low.
Hydrometers measure the density of water, or beer, and can tell you about the fermentation progress.
Because sugar in a liquid increases the density, a reading taken before fermentation should be higher than at the end, when the yeast have converted it into alcohol and gas.
This means that with two hydrometer readings (before and after) you’ll be able to judge whether fermentation has taken place.
Monitor Your Beer
One way to check is to compare your readings with the predicted gravities given by the recipe.
However, as most brewers don’t get exact matches of sugar profile even when following the same recipe, another way to check is to take two hydrometer reading separated by a day or so.
If the density hasn’t changed your beer’s probably done.
So, When to Bottle?
As a minimum wait until primary fermentation has completely finished, usually after four or five days.
Wait another week so the yeast can clean up your beer and your taste buds will thank your patience.