How to carbonate your homebrew in bottles

Fermentation finishes, you have a look in the fermenter, and the beer in there is completely flat, which is exactly right and catches nearly everybody the first time. All the carbon dioxide the yeast made over the last week or two has been bubbling straight out through the airlock, so the fizz has to go back in afterwards, and that is what carbonation is.

There are two ways to do it. You can give the yeast a small feed of sugar in the bottle and let it make the gas for you, which is bottle conditioning, or you can put the beer in a keg and push carbon dioxide into it under pressure. Kegging gear is not part of our homebrew range, so if that is the road you are going down you will be getting the keg and the gas from somewhere else, and that is totally fine. Everything below is the bottle method, because it is what every kit is set up for and it is what nearly everyone actually does.

What is happening inside the bottle

When you bottle, there is still live yeast in suspension even though the beer looks clear enough, and that yeast has simply run out of food. You give it a measured feed of sugar, you cap the bottle, and it eats the sugar and makes carbon dioxide the same way it did in the fermenter. This time the gas has nowhere to escape to, so it dissolves into the beer, and a fortnight later you have got something with a head on it.

That is the whole mechanism, and once you have got it in your head the rest of this makes sense, because every carbonation problem comes back to one of four things: too little priming sugar, too much of it, yeast too cold to do the job, or beer that went into the bottle before it had finished fermenting.

Priming sugar, and the easy version

Dextrose is the usual choice for priming because it ferments out cleanly and leaves no flavour of its own behind. Plain white sugar works too and plenty of people use it without any trouble. Malt extract works as well, though it is slower to go and you need a bit more of it.

If you are bulk priming, which means stirring the sugar through the whole batch just before you fill the bottles, weigh it rather than guessing, because the gap between a nicely carbonated beer and a bottle that goes off like a party popper is only a few grams either side.

The easier route, and the one I would point a first timer at, is carbonation drops. They are pressed sugar tablets, you put the number the packet gives for your bottle size into each bottle, and the measuring is done for you. It costs a little more per batch than a bag of dextrose and it takes away the one step where a beginner is most likely to come unstuck.

Bottles and caps

Brown glass beats clear or green, because light gets into beer and makes it taste skunky, and brown glass blocks most of it. Glass bottles take a crown seal and you need a capper to put them on, either a hammer capper you hit with the heel of your hand or a bench capper you work with a lever. PET bottles take a screw cap and need none of that, which is why the kits come with them.

Whatever you use, everything that touches the beer gets sanitised first. Cleaning takes the residue off and sanitising kills what is left on a surface that is already clean, and those are two separate jobs rather than one.

Where to leave them, and for how long

Bottles want somewhere at room temperature, above 18 degrees, for about two weeks. Cold yeast will not carbonate, so a batch sitting in an unheated shed through the coldest part of the year can look for a month like you have done something wrong when the only thing wrong with it is the temperature.

After the two weeks, put them in the fridge for a couple of days before you open one. Carbon dioxide dissolves better into cold beer, so a properly chilled bottle pours with a head on it while the same bottle at room temperature will gush up the side of the glass and half of it ends up on the bench.

Flat beer and bottle bombs come from the same place

Flat beer is almost always too little priming sugar, or bottles that have been too cold to get going. Give them another week somewhere warmer before you write the batch off, because slow is far more common than dead.

Bottles that blow their caps off, or worse, come from either too much priming sugar or beer that was bottled before fermentation had actually finished, so the yeast still had a feed in the beer on top of the one you gave it. The hydrometer is what settles that, and a reading that has not moved in two or three days means fermentation is done. Bubbles in the airlock do not mean anything at all, because a lid that is not quite sealed will let the gas out somewhere else entirely and the airlock will sit there looking idle while the beer ferments away underneath it.

Shop related products

• Coopers Dextrose 1kg. The standard priming sugar, and it ferments out without leaving a taste behind.
• Coopers Brew Enhancer 2 1kg. Goes in on brew day and gives you the body and head retention that make the carbonation worth having.
• Coopers Original Draught 1.7kg. A forgiving tin to practise the whole process on.
• Coopers Light Malt Extract 1.5kg. For priming with malt instead of sugar, or for building body into the next batch.

The rest of it is in the homebrew collection, and the Coopers range is here.

Did you know we also stock the bottling gear in store, including carbonation drops, PET bottles and PET bottle caps, crown seals in packs of 100 and 250, hammer cappers and bench cappers, bottle brushes, a 2 scale hydrometer with the test jar, glass thermometers and no rinse sanitiser. A fair bit of the homebrew range carries our supplier branding so it does not go up on the website. Give us a ring on (08) 8536 4333 to check what is on the shelf.

If you want to work out a batch before you come in, Brewhilder is our homebrew helper and it will talk you through it.

More from the brewing bench

• What fermentation actually does, and how to keep yeast happy
• How to store your homebrew so it still tastes right
• Top 5 common homebrewing mistakes and how to fix them

Waiting the full fortnight is the hardest part of brewing and I am no better at it than anybody else.

Cheers,
Candeece