Tiny Bubbles A Primer on Beer Carbonation Chris Saunders May 1, 2017 A Primer on Beer Carbonation 1/40
Chemistry Overview Molecular Weights, Units & Constants Ideal Gas Law Henry s Law CO 2 in Beer What is a Volume? Calculating Volumes of CO 2 Post-fermentation CO 2 in solution Carbonating Beer Natural Carbonation Carbonating with Sugar/Speisse Capping Concerns Force Carbonation Keg Carbonation Carbonation Stones Concerns A Primer on Beer Carbonation 2/40
Molecular Weights, Units & Constants Molecular Weight Mass of a molecule of a substance, based on 12 as the atomic weight of 12 C Avagadro s Number 6.022 10 23 The number of units in one mole of any substance, as defined by it s molecular weight. Example The molecular weight of CO 2 is 44.01 g/mol A Primer on Beer Carbonation 3/40
Example - How many moles are in 65g of CO 2? mols CO2 = 65g 44.01g mols CO2 = 65 g mol mol 44.01g mols CO2 = 65 44.01 mols mols CO2 = 1.47693706mols A Primer on Beer Carbonation 4/40
Molecular Weights, Units & Constants Cot d Universal Gas Constant R Physical constant that is used in many fundamental equations in physical science such as the ideal gas law. Sometimes seen in chemistry textbooks as R = 0.0821 L atm K mol Though we will be using the constant for PSI since that s what brewers typically work in [4] R = 1.2059 L PSI K mol A Primer on Beer Carbonation 5/40
Ideal Gas Law[1] PV = nrt P: Absolute pressure in PSI V: Volume in Litres R: Universal Gas Constant T: Temperature in Kelvin A Primer on Beer Carbonation 6/40
How man grams of CO 2 in 1L at Standard Temperature and Pressure (STP)? P = 14.7PSI T = 32 F = 273.15K V = 1L PV = nrt 14.7PSI 1L = n 1.209 L PSI n = 14.7 PSI 1 L 1.209 L PSI K mol 273.15 K K mol 273.15K n = 0.044513304mols g CO2 = 0.044513304 mols 44.01 g mol g CO2 = 1.96g CO 2 / L A Primer on Beer Carbonation 7/40
How many grams of CO 2 the following 1/2bbl keg? Pressure gague is reading 28 PSI Temperature probe shows 46 F V = 1/2 bbl 117L/ bbl = 58.5L C = ( F 32) 5 9 T = 273.15K + (46 32) 5 9 T = 273.15 + 7.78 = 280.93K P = 28(gauge) + 14.7(atmospheric) = 42.7PSI A Primer on Beer Carbonation 8/40
Grams CO 2 in keg? Continued Calculate the number of moles of CO 2 PV RT = n RT RT n = PV RT n = n = 42.7PSI 58.5L 1.2059 L PSI K mol 280.93K 42.7 PSI 58.5 L 1.2059 L PSI K mol 280.93 K = 7.374mols g CO2 = 7.374mols 44.01 g mol = 324.53 A Primer on Beer Carbonation 9/40
Henry s Law The concentration of a [slightly soluble] gas in beer [such as CO 2 ] is directly proportional to the pressure of that gas in the gaseous phase at a constant temperature. [2, p. 65] A Primer on Beer Carbonation 10/40
How do we get CO 2 into beer? How carbonated we want our beer to be (Volumes of CO 2 )? How much liquid we are going to carbonate? How much headspace is there going to be? What temperature is our beer at? (If kegging) A Primer on Beer Carbonation 11/40
What is a Volume? A Primer on Beer Carbonation 12/40
Calculating Volumes of CO 2 As per Henry s Law, the amount of CO 2 in our beer is proportional to the headspace pressure and a constant temperature. If either of these values change, independently we will end up with a different level of carbonation. A Primer on Beer Carbonation 13/40
Calculating Volumes of CO2 Using a Table A Primer on Beer Carbonation 14/40
Calculating Volumes of CO 2 Using a Formula There are numerous formulas which try to approximate the ASBC carbonation lookup tables. A. J. delange developed a formula to approximate the CO2 table curves[6, p. 3] Determine Volumes CO 2 given known gauge pressure and temperature V = (P gauge + P atm ) (0.01821 + 0.090115e ( T F 32 43.11 ) ) 0.003342 e: natural logarithm base ( 2.71828) P atm : is atmospheric pressure, which is 14.7 PSI A Primer on Beer Carbonation 15/40
Calculating Volumes of CO 2 Using a Formula Cot d Since the formula is an algebraic equation, we can move known values around in order to solve what gauge pressure is required to hit our desired level of carbonation. Required gauge pressure to reach desired vols CO 2 V +0.003342 P gauge = P ( T 32 0.01821+0.090115e 48.11 ) atm A Primer on Beer Carbonation 16/40
Example What gauge pressure is needed for 2.6 vols at 34 F? Using Formula 2.6+0.003342 P gauge = 14.695 0.01821+0.090115e 2/48.11 P gauge = 2.603342 0.10465426 14.695 P gauge = 10.18PSI Using Lookup Table A Primer on Beer Carbonation 17/40
How does beer stay carbonated? A net transfer of gas into the beer will continue so long as the pressure of the gas in the headspace above the beer is higher than the pressure of the gas in the beer. [2, p. 65] A Primer on Beer Carbonation 18/40
Post-fermentation CO 2 in solution Even at atmospheric pressure there is going to be some CO2 dissolved into solution. This is highly dependent on what the highest temperature your beer was held at post fermentation. This is why lagers take longer to show active fermentation and gravity samples need to be degassed. A Primer on Beer Carbonation 19/40
Example - How many Volumes of CO 2 are left in finished beer at 15 C? P gauge = 0 T = 15 (5/9) + 32 = 59 V = 14.7 (0.01821 + 0.090115e (59 32)/43.11 ) 0.003342V = 0.971690645 = 0.97vols A Primer on Beer Carbonation 20/40
Carbonating Beer There are many ways to carbonate the product. The most common ways are: Natural carbonation via sugar / speisse Natural carbonation via capping Force carbonation from CO 2 tank A Primer on Beer Carbonation 21/40
Natural Carbonation Easiest form of carbonation to perform Is said to produce a more delicate carbonation Use less CO 2 when kegging Usually the starting point for most homebrewers A Primer on Beer Carbonation 22/40
Carbonating with Sugar/Speisse Fermentables are added back into the product after fermentation has finished completely Unless you are trying to be all Bavarian Purity sugar is an excellent tool The most common sugar used is Dextrose which is 90% fermentable. This makes calculating sugar additions very easy Using wort or malt extract can be done but you need to know how fermentable it is. If using same wort, need to account for it and save some. A Primer on Beer Carbonation 23/40
Getting the CO 2 from your sugars Not all of the fermentable sugars are converted into CO 2. About half of the extract is converted into alcohol and other by-products with about 46% being converted into CO 2 [2, p. 66] Fermentables that can be used for carbonation [3] Name % Fermentable Why? Corn Sugar (Dextrose) 90% Monohydrate Table Sugar 100% Demerara Sugar 100% Honey 75% Dissolved solids Maple Syrup 65.2% Dissolved solids Briess Light DME 75% Contains unfermentable dextrins A Primer on Beer Carbonation 24/40
Example - How much dextrose is needed to carbonate 20L of beer to 2.6 vols? Beer finished at 15 C: 0.97 vols CO 2 Need to add 2.6 0.97 = 1.63 vols 1 vol CO 2 is 1.96g / L, so need 1.96g/L vol 1.63 vols = 3.19g/L Required fermentable extract per litre 3.19g/L 0.46 = 6.93g/L Required dextrose per litre 6.93g/L 0.90 = 7.7g/L Required dextrose for batch 7.7g/ L 20 L = 154g A Primer on Beer Carbonation 25/40
Capping Commonly used by English brewers in which nearly finished beer is transferred into casks and capped off. The beer finishes fermentation in the cask and all the CO 2 is absorbed into solution. Challenges Requires close monitoring of fermentation in order to cap at the right moment Need to know what the fermentability of your wort is Capped vessel needs to be able to hold the pressure (unitank, keg, etc.) A Primer on Beer Carbonation 26/40
Example At what gravity do we cap to get 3 vols? Forced ferment shows a final gravity of 1.010 (2.5 Plato) Determine how many g/l of CO 2 we need 3.0 vols 1.96g/L/ vol = 5.88g/L How many grams of extract is this? 5.88g/0.46 = 12.78g Convert to Plato 12.78g/1000g/L = 1.278 P Cap the fermentor at FG + Carb extract = SG cap 2.5 P + 1.278 P = 3.78 P => 1 + (3.78 4)/1000 => 1.015S.G. A Primer on Beer Carbonation 27/40
Concerns with Natural Carbonation Need to be confident with determined final gravity Packaging before terminal gravity over-carbonation, gushers, or exploding packages Forced fermentation testing is your friend! When adding fermentables also need to consider filling headspace with CO 2 for proper equilibrium pressure i.e. How much sugar do we need if we want to carbonate 35L of beer with 15L of headspace Calculate extract needed for solution Calculate extract needed for headspace Capping requires very precise timing Capping too late uncarcarbonated beer Capping too early overcarbonated Spunding can provide a more user-friendly approach A Primer on Beer Carbonation 28/40
Force Carbonation Instead of letting yeast add CO 2 to our product, we use manufactured gas and force it into solution. You don t know what process your CO 2 is coming from. In rare cases may contain by-products that are bad to your health. New installations can be tricky to debug. Verify that your new setup doesn t have any leaks by spraying everything with soapy water. Slow leaks are an expensive way to end up with flat and oxidized beer. A Primer on Beer Carbonation 29/40
Keg Carbonation Most common approaches for homebrewers Set it and forget it via gas post Rock and roll carbonation method Burst carbonation Remember Henry s Law! Beer won t easily carbonate at 20 C without tons of pressure Set low pressure to prevent a vaccuum and get that beer super cold Once beer is at carbonation temperature adjust your gauge Use formula or Zahm & Nagel carbonation chart A Primer on Beer Carbonation 30/40
Keg Carbonation Gotta go fast! Carbonation happens faster when the surface area of CO 2 exposed to liquid is increased Gas in post: Only the top surface of the beer is exposed to the gas Slow uptake in carbonation Bev out post: Bubble the gas through the cold beer Bubbles have more surface area faster dissolution of CO2 into the beer Slightly higher pressure to overcome pressure of the beer and headspace Carbonation Lid: bubble gas through a carbonation stone Fastest way to carbonate a beer Stone creates very tiny bubbles lots of surface area!! A skilled user can carbonate hundreds of hl of beer in a matter of hours A Primer on Beer Carbonation 31/40
Carbonation Stones Magic? Not really Carbonation stones get so many tiny bubbles passing through the beer that the CO 2 gets absorbed into the liquid much more quickly. When using a carbonation stone you need to mindful of the pressures you are playing with. Too low and the gas won t go through the stone Too high and you ll pull off volatiles and create foaming in your tank / keg A Primer on Beer Carbonation 32/40
Carbonation Stones Wetting Pressure In order to use your stone correctly you first need to figure out what it s wetting pressure is. Finding the wetting pressure[5] Ensure carbonation stone is clean & not plugged Caustic / PBW wash after use Acid washing helps remove protein buildup (Nitric or Acetic Acid) Hook up carbonation stone to CO 2 supply Submerge stone in water and turn up the pressure until you start seeing fine bubbles Also verify that your setup doesn t have any other leaks Record the regulator setting Slowly turn down the pressure until gas stops passing through the stone Record this value as well can help with debugging future carbonation issues A Primer on Beer Carbonation 33/40
Carbonation Stones Operation Wetting pressure isn t everything! Also need to deal with head pressure along with any hydrostatic pressure from the beer itself Every 28 inches (71 cm) of beer adds 1 PSI not really a problem for most homebrewers Need to know what your equilibrium pressure for desired carbonation level A Primer on Beer Carbonation 34/40
Example What pressure is required for this carbonation stone? Want to carbonate a 20L keg at 40 F to 2.4 vols Wetting pressure of stone is 4 PSI Equilibrium Pressure: 10 PSI Hydrostatic Pressure: 0 PSI Wetting Pressure: 4 PSI Regulator Pressure: 14 PSI A Primer on Beer Carbonation 35/40
Example What pressure is required for the same stone the following BBT? 280 of beer in BBT at 44 F to 3.0 vols Equilibrium Pressure: 18 PSI Hydrostatic Pressure: 280 28 = 10 PSI Wetting Pressure: 4 PSI Regulator Pressure: 32 PSI!!! A Primer on Beer Carbonation 36/40
Force Carbonation Concerns Carbonating in Keg Carbonating from gas post may be slow Carbonating from bev post is faster. Check valves are a must! Burst carbonation can result in over-carbonation Shaking can damage foam forming proteins and introduce haze Using carbonation stones Require a bit more work to operate Via venting can carbonate beer very fast Incorrect use can scrub away aromatics and damage foam stability A Primer on Beer Carbonation 37/40
Summary I Chemistry Overview Molecular Weights, Units & Constants Ideal Gas Law Henry s Law CO 2 in Beer What is a Volume? Calculating Volumes of CO 2 Post-fermentation CO 2 in solution Carbonating Beer Natural Carbonation Carbonating with Sugar/Speisse Capping Concerns Force Carbonation Keg Carbonation Carbonation Stones Concerns A Primer on Beer Carbonation 38/40
References George Fix. Principles of Brewing Science. Brewers Publications, 1999. Stephen R. Holle. A Handbook of Basic Brewing Calculations. Master Brewers Association of the Americas, 2010. homebrewtalk wiki - Fermentable Adjuncts. Sept. 2013. url: http://www.homebrewtalk.com/wiki/index.php/ Fermentable_adjuncts. Values of the Universal Gas Constant R in various units. 2016. url: http://www.katmarsoftware.com/gconvals.htm. Jim Tomczyk Dave Meheen Marty Velas. Carbonation Demystified: Carbonation Basics, Natural Carbonation and the CO2 Supply. A. J. delange. CO2 Volumes in Beer. url: http://www.wetnewf.org/pdfs/brewing_articles/co2% 20Volumes.pdf. A Primer on Beer Carbonation 39/40
Questions? Chris Saunders http://famouslastworts.com A Primer on Beer Carbonation 40/40