What Causes Flat Beer?

Flat beer is caused by distribution methods which use compressed air or the improper mix of beer gas (25% CO₂). A 25% CO₂ mix does not have enough CO₂ to properly dispense of most non-nitrogenated (domestic) draught brands, causing beer to go flat.

Flat beer is wasteful because you are putting extra (poor quality) beer in every glass. An ideal 5/8" head is the equivalent of 4% of a pint, so by pouring flat beer your bar loses 4% of the beer revenue.

Air is one of beer's worst enemies; it begins to destroy the product immediately on contact. The oxygen content of the air acts as a flavour contagion, contaminating the drink with the flavours that the air has been exposed to – every flavour in the room. Additionally, air contributes to the growth of several organic contaminates, requiring more frequent line cleaning.

A Great Gas Blend Means a Great Pint.

There are many components in a draught beer system that influence pouring a great pint of beer. Using the proper gas mixture is one of the most important factors.

All draught beers are brewed with a certain amount of carbon dioxide dissolved into the beer and it is important to maintain that level of CO₂. The BGS system provides two blends of gas. A 75% nitrogen and 25% CO₂ for "nitrogenated" beers like Guinness, Kilkenny, Caffrey's etc which have a relatively low carbonation content (1.2 volumes) and a 50% N₂ and 50% CO₂ for domestic and craft beers which have a higher CO₂ content (approx. 2.5 volumes). Maintaining the carbonation content in beer allows you to pour the proper "2 finger" head on every beer from the top to the bottom of each keg resulting in increased yields and profits for your establishment.

Nitrogen is the perfect choice as a second gas for several reasons. Many beers use nitrogen as an ingredient. The best-known example and the originator of the concept is Guinness Stout on draught. The Guinness brewers go to great pains to dissolve nitrogen in the beer, which improves the quality of the head. Nitrogen (N₂) is the ingredient responsible for the "whippedcream-like" foam in Guinness and other beers like Kilkenny, Boddingtons, Caffrey's, and Murphy's Stout. N₂, in the right proportion, is required in the gas used to push these beers. Without it, the dissolved N₂ would come out of solution and these beers would not be the same.

Nitrogen is one hundred times harder to dissolve in beer than CO₂. While this is a challenge for the brewers mentioned above, it makes N₂ a good choice for dispensing "normally carbonated" beers. N₂ is not readily absorbed, does not react chemically under normal circumstances and will not affect beer flavours. N₂ is 78% of the air we breathe, making it safe and readily available. A relatively new product called a "Nitrogen generator" is available from several sources in the Canada today. Nitrogen generators filter relatively pure N₂ from air and can be a very economical source of Nitrogen. They can be built or used with a blending device and a CO₂ source to provide all the gas for any bar or facility.

What Causes Foamy Beer?

Foamy beer is caused by the use of 100% carbon dioxide as a dispense gas in draught systems. By using solely CO₂ to pressurize the beer, the total concentration of CO₂ in the beer skyrockets, creating foamy beer from the taps. This is manifested as excess head, which is poured out into the tray by the bartender as wasted product. It also creates foamy residue in the keg, meaning that an additional 5% of each keg's beer is wasted.

Finally, the greatest offense of foamy beer is to the customer. Excess head that must be poured out spills over the side of the glass, making it wet and sticky. Furthermore, the raised carbon dioxide content distorts the flavour of the beer, causing it to taste sharp.