Whether it ’s stand proudly at the center of a company or hiding discretely in the back elbow room of a pub , the keg is the vas of choice forbeer . That ’s why more than 60 million gallons of beer are sell in keg every class . It ’s also why those that knowhow to tap a kegare priceless .

Kegs sure are awing . After all , what good fashion could there be to move that precious liquid around than in a big , round barrelful that can be rolled , heap and tapped ? No need to worry about nursing bottle caps or broken glass ; the keg is fabulously long-lived , requires no cap and is completelyrecyclable[source : Beer Institute ] .

But what ’s give way on inside a kegful ? And more significantly , how on the button does one unlock the golden brown elixir pin down within ? While beer nursing bottle are sheer , kegs bring out nothing of the complex and uneasy chemical substance armistice that ’s been established in their dark interiors , nor of the technology that makes them work .

When we press on the tap of a kegful at a party , or when we order up a dry pint at the measure , we take it for granted that beer will fall forward with just the right proportions of foam , carbonation , coolness and flavor . But the truth is that a great deal of cerebration has go into achieving that complete balance .

What Is A Keg?

A keg is a fancy version of your canonic barrel . In the factory , a canvass of stainless steel is roll into a cylinder and welded together . Then , at the piston chamber ’s midpoint , a set of ribs is press into it for impart rigidity . Next , top and bottom blade crustal plate are stamped out and likewise welded into place .

The steel in question , a peculiar alloy of chromium , nickel , manganese and several other component , is used because it welds flawlessly leaving a smooth joint – this is very important for a nutrient - grade container because you do n’t require any scratchy surface where bacteria can set up shop . [ source : nickelinstitute.org ]

The airtightness of a keg is unbelievably important – it ’s what go on the beer from becoming monotonic and flavorless . Still , the beer has to add up out somewhere , and that ’s why there ’s a spear . The spear is a long metallic element tube that reaches almost to the bottom of the kegful . Despite its warlike name , the spear is basically a grown metal stalk through which beer can move up from the bottom of the keg and out through the tap at the top [ source : nickelinstitute.org ] .

Just what are taps , and why do English and American brews refuse to add up out of the same one ? We ’ll get to that in a bit . Right now , let ’s come up out why all kegs are not created adequate .

How to Tap a Keg

Few thing kvetch off a party more effectively than tapping a refreshed kegful . It ’s a striking too . But do n’t take my word for it , just watch how fast the line forms follow the welcome hiss of a freshly tap keg . But there ’s a band of pressure on the the one doing the tapping , both literally and figuratively . fortuitously , it really is n’t all that complicated .

Before you get the beer flowing , verify you do everything that you’re able to to keep the keg cold . If the beer is n’t cold enough , you ’ll likely have a lot of foam on your hand . So lease the keg rest in one touch for at least a few hours before tap it to prevent ardent beer or too foamy beer [ origin : homebrewingadvice.com ] .

Once the beer is dusty enough , and has acclimate to it ’s environment , it ’s time to tap . Do so by following the steps below :

Types of Kegs

When a pub ordering up its draughtbeersupply , ordinarily what ’s delivered is a truckload of received keg recognise as " half barrel . " The half - bbl is also the garden - change kegful unremarkably nest in a big bucketful of ice at afratparty . It ’s called a half - bbl because the " barrel " is a legal unit of measurement of measure used for consequence and export statistic .

In the U.S. , a barrel , by definition , is 31 gallons ( 117 litre ) of fermented potable . So , as you might have guessed , a half - gun barrel holds half that amount – somewhere between 14 and 16 gallons ( 53 - 60 cubic decimeter ) , or by a more agreeable measure , 124 pint ( 117 metric pint ) . This is slightly larger than the 50 liter ( 13 gallon ) stock European keg . Fill either kind of kegful with beer , and you ’ve get an target press about 160 pounds ( 73 kilograms ) . By line , an empty half keg is a sole but hardly insubstantial object that weigh roughly 30 pounds ( 14 kilograms ) [ source : Wayland Works ] .

If you ’re at a smaller party where the great unwashed are n’t jump raw into the consortium and spray skimming cream all over somebody ’s car , then you might play a more civilized vessel – the quarter keg , aka the " pony keg . " It ’s called a pony because , like ponies , the quarter keg is little – but it can still support 90 pounds ( 41 kilograms ) of beer . [ sources : Wayland Works , Word Detective ] .

For the sedate dinner party company , there ’s the refined and aerodynamic " torpedo keg " ( or the " 6th cask " ) which holds a little more than 5 congius ( 19 l ) . And for an eve with friends , there ’s the very quiet " mini - keg , " dearly know as " bubba , " which provides a pleasant 10 and a half pints ( 10 metric pints ) with which to while off the football game . Last but scarcely least is the Beer Ball , a charge card number cradle 5 gallons ( 19 liters ) in its slender inside [ source : Micromatic ] .

There are other , more arcane vessels waylay in the margins of beer culture . The Cornelius , or " corny " keg , is the canonical soda canister shot that servers are always changing at riotous - food joint . Capable of holding 5 Imperial gallon ( 19 liter ) of liquid , the corny keg was long ago identified by home - brewer as the ideal vessel for their purposes . [ source : Brew Ware ] .

All kegs , no matter their sizing or style , must plow with the same vital issue : how to get the beer out . On the next page we ’ll blab about the complex challenges this on the face of it simple job present .

Beer Keg Pressurization

Steelkegs are build up to hold out pressure , both from the outside and the interior . With somebeercontainers ( caskful , mini - kegs , torpedoes and beer glob ) the spout is often at the bottom of the vessel , and gravity forces the beer out of the strike when it ’s opened . But when it number to the average keg , the rap is at the top . So what attain that beer defy gravity and menstruate through the tap and beer line at will ? In a word , pressure . But make that pressure is a wily business [ source : Wayland Works ] .

When the great unwashed talk about air pressure in beer kegs , they stand for the violence exerted down onto the surface of the beer , forcing it up through the spear . What exerts that pressure may differ . The average company keg uses , appropriately enough , a " company heart . " political party pump are simple and cheap . All you do is pump them a few times , and that builds up enough insistence to force a dry pint of beer up and out the tap . But what you ’re pump into the kegful is melody , and one of the thing that makes up air is O .

Our lung love O , but beer really does n’t . Oxygen tends to destabilize the complex tang and aromas in a beer while at the same metre absorb the carbonation . This means that in the blank of a day or two , the contents of the kegful will be both tasteless and flat . Not a problem for a well - attended party , but also not an option for a pub that might take weeks or months to go through a unmarried kegful [ source : Brew Ware ] .

That ’s why some clever beer lovers came up with the idea of a tap system , which maintain the press inside a keg by feed pressurise CO2 or N into it at a constant rate . Of naturally , this means that you have to have a tank of the stuff W. C. Handy .

Carbon dioxide alone go pretty well , and for some beers , CO2 commingle with atomic number 7 is even better . It ’s all about keep up the natural carbonation in a beer – and carbonation is … CO­2 . So when pressurized CO2 dissolves into the beer , it ’s just total more of what ’s already there .

But there can be too much of a good thing . redundant carbonation can make plough beer into a big glass of fizz . That ’s why nitrogen can be so handy : Like CO2 it ’s more or less tasteless and odorless , but unlike CO2 it does n’t disband well into beer . A skillful mix of the two gases can asseverate the natural carbonation in the beer without upsetting the equilibrium of its savor and olfactory property [ source : Wayland whole shebang ] .

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