How to Carbonate Your Beer Naturally

A Primer on Priming: How to Carbonate Your Beer Naturally

Carbonation for a beginning homebrewer can be very easy. Boil the packet of corn sugar that came with the kit and mix it in, right?

Well, there’s a lot more to understanding the priming process than simply knowing how much you usually put in. Many brewing styles use different levels of carbonation to achieve their distinctive mouthfeel, and it helps to understand how your choices, when carbonating with sugar, can affect the mouthfeel of your finished product.

Know Your Beer Style

Most ingredient kits come prepackaged with 4 ounces of corn sugar. Some homebrew shops don’t even vary this amount by the style in the kit, so your Irish Stout has the same carbonation as your IPA. Unfortunately, this can hurt the overall effect of your beer.

IPA’s have higher carbonation than stouts in order to help carry the hop aromas up out of the glass and to your waiting nose. The stout, however, depends on lower levels of carbonation to help achieve the smoother, velvety mouthfeel. Think about how Guinness feels on your tongue, and then think of how Lagunitas IPA feels on your tongue. They are different experiences in part because of their carbonation levels.

Choosing the right carbonation level for the beer style you’re brewing is key. The BJCP Style Guidelines are a great guide for carbonation levels, but I’m also including a reference for some common styles below:

• British Pale Ale (Bitter, ESB, etc.) — 1.5-2.0
• Porters and Stouts — 1.7-2.3
• Belgian Ales — 1.9-2.4
• American Pale or IPAs — 2.2-2.7
• German or Czech Lagers — 2.2-2.7
• Belgian Sours — 2.4-2.8
• Wheat, American — 2.7-3.3
• Wheat, German — 3.3-4.5

To calculate the amount of sugar to use for this beer, you just need to know how much beer you have, what your target carbonation is, and what kind of sugar you’ll be using.

Know the Limits of Your Bottle

Beer bottles aren’t dangerous until they are over-carbonated. Then they become the deadliest weapon in a homebrewer’s arsenal of mistakes.

Make sure you know how much pressure your bottles are rated for, and don’t try to hit the high end of the carbonation scales unless you have confirmed your bottles are rated for it. The Belgian Sours and American Wheats at higher carbonation levels can really push some glass bottles to the edge, especially if the brewer makes a measuring mistake.

Choosing the Right Sugar

You can technically carbonate with any kind of fermentable sugar, but no matter what kind you use always measure by weight, as measuring by volume is horribly inconsistent.

Corn Sugar:

Corn sugar is the most common because it does not add any significant flavor contributions and it is pretty inexpensive. For 5 gallons of beer, 4 ounces (again, by weight) of corn sugar should yield you right at 2.5 volumes of CO2 in your beer, which is about average for an American Pale Ale.

Table Sugar / Cane Sugar:

Table (cane) sugar is a good option if you find yourself without corn sugar on bottling day, but be sure to measure it by weight, not volume, as some companies grind their sugar finer than others. This can lead to over or under carbonation. It, too, offers little in the way of flavor additions at the volume used for priming. Keep in mind, too, that cane sugar carbonates just a bit more than corn sugar, so if you’re pushing the limits of your packaging, you may want to take it easy here.

Malt Extract:

Malt extract is another common choice, as a lot of brewers already have this around, and like the idea of avoiding the introduction of adjuncts to any stage of their brewing process. To use malt extract, you’ll need more than you would of cane or corn sugar. Also, watch for the hot break in the boil process. It can cause boil overs, which aren’t a problem for the sugars.

Honey:

Honey should typically be avoided at bottling, as it is difficult to know the gravity of honey without first diluting it and taking a gravity reading, which is a royal pain. It’s really just better to go with cane sugar, corn sugar, or malt extract. They tend to be far more predictable.

Brown Sugar, Molasses & Sorghum:

Darker sugars, such as brown sugar, sorghum, or different types of molasses, can add significant aftertaste at bottling, which may be desirable in some beers, especially darker beers. So, just keep that in mind as you make your choice on what type of sugar to use.

For different sugars, you also need to know they offer different amounts of fermentable sugars by weight. For instance, If we use cane sugar as the base, you’ll need 1.1 times as much corn sugar to achieve the same carbonation and 1.3 times as much brown sugar. For using malt extract, you’ll need about 1.5 times as much by weight. Other sugars such as honey, molasses, and sorghum will vary by their weight, and you’ll need to have a good idea of their gravity before proceeding.

OK, but what is a “Volume?”

A volume of CO2 is a measurement of the pressure in the beer. It is essentially shorthand for “a unit of CO2 per unit of beer”. In other words, a gallon of CO2 dissolved into a gallon of beer makes one volume of CO2.

So how do I know how much CO2 is in my beer?

Here’s the really fun part: You probably don’t. The beer comes out of the fermenter with some residual CO2 dissolved in it, and you’re estimating how much sugar you need to add to a closed system to dissolve more CO2 in it to create the bubbles.

It’s pretty much guesswork, except it isn’t. We know how to calculate this because of a guy named William Henry, a chemist who gave us… well, Henry’s Law.

Mr. Henry came up with several laws about how gasses work in our world, and this particular law states this:

“At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid”

Essentially, as long as you know your temperature of the beer, you will know how much CO2 is still dissolved in it from the process. So, when using a priming calculator, make sure and enter the temperature of the beer as it was fermenting, not the temperature it will be sitting at in the bottle.

Here is an estimate of the amount of CO2 in your beer at the fermentation temperature listed:

Temp. (°F)	Vol. CO2		Temp. (°F)	Vol. CO2
32°	1.7		55°	1.1
35°	1.6		60°	1.0
40°	1.45		65°	0.92
45°	1.3		70°	0.85
50°	1.2		75°	0.78

Because of Mr. Henry, we can use charts and handy online calculators to tell us how much priming sugar to use. Brewblogger has an easy one to use. Thanks, Mr. Henry.

Let’s do it by hand!

Yes, I’m a huge nerd, but here’s how we’d do one by hand. Let’s say I have a stout that has been fermenting at 68 degrees, and I’m ready to bottle it.

Because of Henry’s Law, we can know that we already have about 0.9 volumes of CO2 dissolved in the beer. We are aiming for the mid-range volume in our finished product, which is 2.0 for a stout, so we need to find a way to increase our carbonation by 1.1 volumes.

To do this, we need to add 1.1 gallons of CO2 per gallon of beer in our 5 gallon batch, which equals 5.5 gallons of CO2.

A key number to remember is that it takes ½ ounce of sucrose (corn sugar) per gallon to raise that gallon by one volume of carbonation. So, to raise a 5 gallon batch by 1.1 volumes, we would need the following:

So, by adding 2.75 ounces of sucrose to the beer, you increase the CO2 volume from 0.9 to 2.0, which was our target for the stout.

Keep in mind variations as small as an eighth of an ounce per gallon can have a noticeable difference in carbonation. For that reason, it is always advisable to bulk carbonate the whole batch rather than trying to carbonate each bottle individually, as some older homebrewing books might advise.

Carbonating by Batch

To carbonate a batch of beer, boil your chosen priming sugar in about a pint of water on the stove for 10 minutes. Dump this into your bottling bucket, and then siphon your beer on top of it. Make sure to stir the beer, as the sugar may have distributed unevenly in the batch, and this will prevent gushers and flat beers.

Connect your hose to the bottling bucket’s spigot and the bottling wand to the other side. One by one, fill your sanitized bottles to about 1 to 1.5 inches from the top of the bottle, then cap them with sanitized caps.

Give them at least two weeks at room temperature to carbonate, and longer for high gravity beers.