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Force Carbonating Beverages the Inexpensive Way

Want to learn how to build this system?  This site explains how

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    Home brewing beer and soft drinks can be an expensive hobby, especially when filtering the beer and force carbonating.  Home-brewing supply stores sell expensive hardware to filter and carbonate beer, however the hardware store offers less expensive methods for doing this.

Background Information

-How does carbonation work?  

    Henry's law states that the mass of a gas dissolved into a solution is directly proportional to the partial pressure of that gas surrounding/above the solution.  In other words, in order to get Carbon Dioxide into (carbonate) a beverage, it is necessary to have a given amount of Carbon Dioxide pressure surrounding/above the solution.  


-How do you get Carbon Dioxide pressure?

    To get Carbon Dioxide pressure, one can pump Carbon Dioxide into a closed system (force carbonation) such as a keg; or use yeast and priming sugar (in a closed system such as a keg or a bottle) to create Carbon Dioxide pressure (natural carbonation).


-How does yeast make Carbon Dioxide Pressure?

    Yeast eats sugar, this is known as fermentation.  The products of fermentation are Carbon Dioxide and alcohol.  When brewing beer, the wort is allowed to ferment until the yeast has eaten all of the fermentable sugars in the solution (more or less depending on attenuation of the yeast etc...).  This is how beer becomes alcoholic.  Typically, the Co2(Carbon Dioxide) emitted during fermentation is allowed to escape the system (Co2 bubbles out of the airlock), therefore the beer does not become carbonated during fermentation.

    After fermentation there is yeast suspended in the beer, when you add priming sugar (during the bottling process) to the beer, the yeast eats the sugar and gives off a small amount of alcohol, and Co2. This Co2 is trapped inside of the bottle, or keg, and it builds up Co2 pressure.  The Co2 is then absorbed by the beer; when a target amount of Co2 has been absorbed into the beverage, the beer is carbonated.  If too much sugar is added, the beer can become over carbonated (the pressure can build up high enough to cause the bottle/keg to explode) This method of carbonation can take weeks.  This method of carbonating a beverage is called natural carbonation or bottle conditioning.

    While making soda, yeast is added to the solution for carbonation.  The yeast eats some of the sugars in the soda which gives off Co2 and a small amount of alcohol (not a significant amount of alcohol).  The trapped Co2 carbonates the soda.  To stop fermentation (carbonation), the soda is placed into a refrigerator to make the yeast go dormant (yeast will go dormant at a cold enough temperature, this temperature depends on the type of yeast used).  Ale yeast will typically go dormant at 50 degrees or less.  If the yeast was not made to go dormant, it would eat all or most of the sugar in the soda, and the amount of Co2 pressure would build so much that the bottle/keg would explode (not to mention the soda would be moderately alcoholic, and not very sweet). Follow the carbonation instructions on the recipe in order to get the desired carbonation level.


-How does force carbonating work?

    To force carbonate, simply add Co2 pressure to a solution (a beverage in this case).  This is usually accomplished by using a Co2 cylinder and a regulator to add Co2 pressure to a closed system (usually a keg); however, later in this tutorial I will show how to build a pump, capture Co2, then pump it into a mini keg (or a two liter bottle) to carbonate.  

-How much pressure does it take to carbonate a beverage?

    The required pressure for carbonating is dependent upon two things: how much carbonation is desired (Soda is usually about 3 parts Co2 per volume, some English Ales are as low as 1.8 parts Co2 per volume), and the temperature of the solution (soda or beer).  

-How do you use the carbonation chart?

    Check the temperature of the beer/soda [the temperature of the beer/soda is usually a few degrees (F) warmer than the refrigerator that it is in, so just measure the (inside) temperature of the refrigerator, then add a few degrees to get the approximate temperature of the beverage].  Measuring the temperature of the refrigerator is easier than measuring the temperature of the beverage, so this method is preferred.  Once you have the temperature of the beverage, look to the chart to see the desired carbonation level; then look up on the chart to see the required Co2 pressure.  Example, the beverage is at 40 degrees F, and the desired carbonation level is 2.75 parts per volume, therefore the Co2 pressure required is 15PSI.  Click on the following hyperlink for a more comprehensive/complete chart (Microsoft Excel is required to view this chart) Carbonation Chart.xls.

-How much carbonation is typical for different types of beer?

    British-style ales 1.5 - 2.0,  Porter, stout 1.7 - 2.3

   Belgian ales 1.9 - 2.4,  European lagers 2.2 - 2.7

   American ales & lagers 2.2 - 2.7,  Lambic 2.4 - 2.8

   Fruit lambic 3.0 - 4.5,  German wheat beer 3.3 - 4.5

(Carbonation chart and beer carbonation information courtesy of:  )


-How long will it take to force carbonate?

    Depending on the body/gravity of the beer/soda, it might take up to 4 days.  Typically I force carbonate for 4 full days just to make sure carbonation is complete.


-Why filter your beer?  

    The residual/suspended yeast in the wort from fermentation can lead to off flavors, reduced crispness, chill haze, and sediment in the finished product.  However, to naturally carbonate beer/soft drinks, it is necessary to use the residual yeast (or to add yeast, if carbonating soda) to carbonate the beverage.  If you filter out the yeast after fermentation (when making beer), or simply do not add yeast when making soda, naturally carbonating the beverage cannot be accomplished (because the yeast is not present to add Carbon Dioxide to the beverage); therefore, to carbonate the beverage, it must be force carbonated.


-Can you filter the beer, then naturally carbonate it?

   Yes but you must not filter all of the beer.  If you filter 100% of the beer, the answer is no because there will be no residual yeast to eat the priming sugar; thus, natural carbonation is impossible. 

   Since it only requires 10% of the residual yeast to naturally carbonate beer, it is possible to filter 90% of the beer, add the 10% unfiltered beer back into the solution, add the required amount of priming sugar, then bottle.  Once you bottle the beer, it must be kept at a temperature of about 70-75 degrees for about three weeks in order to carbonate the beer.

**Note: when kegging beer (rather than bottling) prime the beer using 1/3 cup priming (corn sugar) sugar (per 5 gallons of beer) instead of the usual 3/4 cup (per 5 gallons of beer) priming sugar for bottling it.

**Note: to prime the beer, boil the priming sugar in 1 pint of water for 5 minutes, let it cool, then add it to the beer before bottling/kegging. (make sure the equipment is sanitized)

**Note:  When Force Carbonating beer, do not prime the beer.

**Note:  When Force Carbonating soda, do not add yeast to the soda.  (If the recipe calls for natural carbonation, but you are going to force carbonate, you might need to reduce the amount of sugar in the recipe slightly because yeast will not be present to eat some of the sugar)


The next page will show how to build a system to capture Co2 and pump it into a keg to force carbonate:

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