Q: Is there a way of carbonating beer through a carb stone that you would recommend? I have seen it done several ways but I am not sure what is the best. should one vent the tank while carbing, carb the tank through the stone while applying head pressure or just push gas through the stone with no vent. Maybe none of these are the best way and you have another technique?
A: Carbonating through a tank requires:
- An ASME pressure rated tank 30 psig (2 bar) is best
- Good refrigeration to hold temperature at a fairly precise level
- Adequate tank over pressure protection, either a pressure-vaccum relief valve or burst disc
Be very careful, high pressure is very dangerous!
As you probably know already the relationship between temperature, pressure and carbonation is pretty well understood. The Zahm chart will give you a good reference for predicting carbonation in volumes of CO2 at different temperatures and steady state pressures. There are different carbonation methods available to brewers. The most elegant (and expensive) are automated carbonation set-ups that will dose and monitor CO2 levels on the fly. There are also in-line carbonators which do a very clean job of injecting CO2 as the beer is pumped through piping on its way to a bright tank.
For smaller operations though the in-tank carbonation stone is still the gold standard. The stainless steel stone should be occasionally cleaned by soaking in acid solutions to clear out beer stone build ups but provides fairly predictable carbonation. The set up should include a back check valve to avoid beer backing into the CO2 line and the CO2 line should be fitted with a 0.2 micron filter. Flush CO2 through the line before connecting to the tank to evacuate out air. Beer to be carbonated should be as cold as possible to reduce the pressure necessary to carbonate and for best CO2 solubility. I do not recommend venting the tank while carbonating as this will volatilize and blow off precious hop oils and aromas as well cause foaming in the tank wasting foam causing components that you want to retain for the beer . Instead apply carbonation slowly to the closed tank up to the pressure needed for the carbonation level desired. Test the carbonation level and make adjustments to the pressure level as needed.