Racking, dry hopping and fining
As the end of fermentation approaches, there are several optional steps brewers can take, including transferring the beer to another fermenter to finish and adding hops. Once fermentation is finished, finings can be added to help settle out the yeast and clear the beer.
Racking is the transfer of the beer from the primary fermenter (the one in which you pitched the yeast into the wort) to a secondary fermenter as fermentation is coming to an end. Some people strongly believe that removing the beer from the yeast cake, hop debris and other "impurities" results in a better-tasing beer than a brew that has not been racked.
On the other hand, many brewers swear that racking has absolutely no positive impact and is an unnecessary step that gives another chance for an infection to be introduced. It's horses for courses. Give it a go and if you believe it is good for your beer, go with it.
Step by step: Racking
The only extra bits of equipment you will need to rack a beer are a second fermenter and a length of food-safe hose. The hose needs to fit on the tap of the primary fermenter and be a little longer than the height of whatever the primary fermenter will be placed on when racking. The reason for this is that when racking the beer needs to run gently into the secondary fermenter with no splashing, so as to avoid admitting oxygen into the beer that at this stage could spoil it.
- Place the primary fermenter (the one full of beer) on a table or bench.
- Sanitise the second fermenter and the plastic hose.
- Place the secondary fermenter on the floor beneath the tap of the primary fermenter.
- Loosen the lid or cling wrap from the primary fermenter
- Draw off a little beer from the primary fermenter to clear any trub from the tap, and discard it.
- Attach the hose to primary fermenter and put it into the seconary fermenter.
- Coil any extra hose it in the bottom of the secondary fermenter to ensure the beer is delivered as gently as possible.
- Make sure the tap on the secondary fermenter is turned off!
- Turn on the tap on the primary fermenter and adjust it to a steady flow. Avoid letting it run too fast and splashing in the secondary fermenter, which would admit oxygen.
- If necessary tip the primary fermenter as the level drops so that the tap remains submerged but no trub is drawn into it.
- When the transfer is complete remove the hose from the secondary fermenter and fit the lid or a piece of plastic food wrap.
- Put the fermenter somewhere for the remainder of the fermentation.
Note: The same or similar method as racking is employed when transferring a beer to be matured in a fermenter or lagered.
Boiling and the fermentation itself drives off aroma and some taste from hops, so adding a portion of hops during or after fermentation helps retain hop character in the beer. This is known as dry hopping. Adding hops at this stage will contribute mainly aroma, perhaps a little flavour and absolutely no bitterness because hops need to be boiled to extract their bitterness.
For more information on dry hopping and other methods of hopping in the primary or secondary fermenter (i.e. after racking) see the section on Adding hops and grain.
Finings are added after fermentation to help yeast drop from suspension to the bottom of the fermenter, or "drop bright". Household gelatine can be used for fining, while isinglass, made from the swim bladder of fish, is a traditional fining agent. Chefs prefer leaf gelatine to powdered gelatine because it does not impart a flavour to the finished dish. For the same reason, use leaf gelatine for fining if you can get it.
In Australia, most homebrewers do not use finings. Fining is most often associated with cask-conditioned ales, so in Britain it is much more popular.
Step by step: fining
If using isinglass, follow the instructions on the packet. If there are none, use the procedure below.
- Confirm fermentation has finished.
- Rack the beer following the instructions above, so that as much yeast as possible is left behind in the primary fermenter.
- If using a leaf of gelatine, soak it in cold water for one minute then gently squeeze out any excess liquid.
- Dissolve a 15g sachet of gelatine, the soaked leaf of gelatine or finings in a cup of hot water.
- Allow the liquid to cool slightly, covered.
- Draw off about 500ml (two cups) of beer.
- Gently mix the beer with the gelatine liquid.
- Tip the mixture back into the fermenter.
- Stir very gently to mix the fining liquid though. Do not be vigorous with the stirring or oxygen will be admitted and risk spoiling the beer.
- Allow the beer to clear for about a day then bottle or keg.
When is my beer ready to bottle or barrel?
The time it takes to ferment the wort will vary depending on how much sugar there is, how much yeast was pitched, the type of yeast and the fermentation temperature. The only definitive and foolproof way to know that the beer has stopped fermenting is that the SG is about the expected final gravity and it has been stable for two consecutive days. The most unreliable way to tell if your beer has finished fermenting is that it stops bubbling through the air lock, because it may well be that the carbon dioxide is escaping through a leak or the fermentation has stalled.
Never bottle a beer that has finished fermenting because doing so risks the danger of creating "bottle bombs", or exploding bottles caused by the build-up of pressure as a result of fermentation continuing in the bottle.
For instructions on taking specific gravity readings and using them to calculate alcohol content in beer, see the section on Specific gravity & alcohol content.