There’s nothing worse than opening your long awaited bottle of home brew only to find the beer flat and lifeless. Thankfully it’s easy to make sure this doesn’t happen.
If you understand why beer has gas in the first place, you can prepare the conditions necessary for it to form.
Why Beer has Gas
The bubbles in beer are produced by yeast as they convert sugars to alcohol and carbon dioxide gas during fermentation.
The gas is normally released from the fermentation bucket through the airlock (signalling to the brewer that fermentation is in fact taking place) so the beer has very little gas at the point of bottling.
If you try the brew at this point it will taste like flat beer.
How to Add Gas to Beer
To add gas to the finished beer, home brewers introduce priming sugar during bottling.
The yeast suspended in the beer ferment these sugars while inside the bottle. Because the bottle is sealed, the gas stays and becomes an integral part of the beer.
Generally, there are two ways of adding the priming sugar: as a solution mixed with the whole batch, or in small quantities put straight into each bottle.
A sugar solution of approximately the same gravity as the beer is mixed (and boiled) and gently stirred into the wort. A typical mix of cane sugar for a 20 litre batch is approximately 110g.
It’s then left to settle for twenty minutes before bottling as normal.
Because you rely on dispersion for the sugar to evenly mix into the beer there’s potential for some bottles to be more carbonated than others.
Often, flat beer comes about for this reason. Don’t be impatient - allow the sugar time to mix into all parts of the wort.
It’s vital in this process that all equipment is sanitised and nothing is allowed to infect the beer.
Every time you mess with the beer there’s a risk of contamination from wild yeast or other bacteria.
Spoonful of Sugar
Some home brewers drop a spoonful of sugar into each bottle before syphoning the beer.
This method is easy but fairly inaccurate and can lead to flat beer or overly gassy brews.
Too much sugar causes excess gas which can potentially explode the beer bottles. The risk of contamination to the beer is slightly less than with a priming solution because no additional liquid is added.
Unless you’ve got a good reason not, avoid this method if you’re hoping for consistency between brews.
Carbonation drops are a variation on the spoonful of sugar method.
These tablets of brewing sugar are put into each bottle to give a standardised dose. The drops ensure that each bottle carbonates equally and avoid the need to prepare a priming solution with the sanitising that that involves.
Of course, you’ll still need to sanitise the bottle tops and syphoning equipment during bottling.
The downside of carbonation drops is the lack of flexibility in terms of flavour.
It’s often interesting to add sugars that complement the beer, such as brown sugar to a dark bitter or honey to a summery ale.
On the other hand, the carbonation drops are flavourless so are a good general solution to a problem.
They’re possibly the easiest way of consistently carbonating home brew, but offer little flexibility.
I’ve Correctly Primed. So Why Is My Beer Still Flat?
If you knew all of the above already, have primed your beer correctly yet still wonder why you have flat beer there are a number of possibilities you could consider:
- The yeast may have settled to the bottom – shake and see if that solves it (a solution from John Palmer)
- The yeast may not have worked yet – it often takes up to two weeks for the yeast to finish production. This is often the case if the home brew releases gas when opened but has little head retention.
- The temperature is too low for the yeast to work effectively. Either move the beers to a warmer area or wait longer.
If you’ve followed the steps above it’s just a matter of patience.
Now you won’t have to worry about flat beer again.
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