(Apologies if the formatting of this is weird, I wrote it in Markdown format and had to convert to BBCode)
What are mini-kegs?
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Mini-kegs (MKs) are large, coated steel cans with a five liter (1.32 gallon) nominal capaticy. They are manufactured by Ball for the European market. The specifications can be found here:
http://www.ball.com/product-catalog/view/beverage-cans/5-litre-party-barrel/
They are rated for pressures of up to 4 bar (around 58 PSI), but in practice they shouldn't exceed around 35 PSI for maximum reusability.
Many German imports are available off-the-shelf in 5 liter mini-kegs, which are reusable. The mini-kegs of Heineken and Newcastle that you see in the grocery store are
not reusable as they are pressurized with an internal CO2 cartridge and regulator device. They do not have a bung closure; instead, they are sealed and can only be opened by cutting. Some American microbreweries like Bell's, Rogue, and Widmer have also started distributing select beers in (reusable) MK form - hopefully this will be a trend!
Why would I use mini-kegs instead of Cornelius kegs?
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I love MKs for the following reasons:
1. I make small batches
2. I don't drink a whole lot of beer, and I don't want 5 gallons of beer sitting around for months and spoiling while I slowly chip away at it
3. I can drink a variety of beer and change it often
4. They are extremely portable and easy to fit in any fridge or cooler
5. They are cheap (free if you reuse the ones you got beer in!)
In short, they are perfect for me, and they might be for you too! Or they might not.
Will I save money by using mini-kegs?
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The short answer is: not a lot, but some. If you are considering mini-kegs just to cut costs, you'll likely be disappointed.
If you brew normal five gallon batches, you won't save anything. It takes four mini-kegs to keg a five gallon batch, and for the price of four new mini-kegs you could get a used five gallon Cornelius keg and likely be happier.
Small batch brewing is where mini-kegs shine. If you brew one- or 2.5-gallon batches, and currently bottle them, mini-kegging may be for you. A small 2.5- or three-gallon cornelius keg is difficult to find used, and new they can range from $70-120. A one-gallon batch will fit in a single $12 mini-keg, and a 2.5- or 3-gallon batch will typically fit in two of them (with perhaps a few bottles worth left over). That is already a savings.
However, to have a draft system, you will still have to invest in:
1. A CO2 cylinder
2. A CO2 regulator
3. A CO2 manifold
4. Gas and dispensing hardware
These make up the bulk of the startup cost for any kegging system. However, if you ever decide to upgrade from mini-kegging to regular kegging, these components can all be brought over to the corny keg system! So rest assured that you won't really be wasting any money on starting with mini-kegs.
In addition to the common draft hardware, you'll also need a mechanism to tap the mini-kegs. We'll get into that later on.
Types of mini-kegs and closures
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There are actually several different varieties of mini-kegs.
I've already mentioned the common reusable mini-keg.
These come with several different type of closures.
The reusable closure is made of gray rubber, with a white plastic insert. These are manufactured by Wecomatic GmbH, a German company. Two different inserts are available, Hermetic and Hermetic PS. The Hermetic PS gives you a better seal due to the wide, solid disc; the ones you get from homebrew shops are usually the regular Hermetic inserts which are hollow plastic with a small ring on the inside
When you buy a mini-keg of German beer, look for the gray bung. That tells you it's reusable. Also, a bonus is that these kegs are usually sealed with the Hermetic PS insert, which is otherwise difficult to obtain in the U.S. Kostritzer Schwarzbier and Bitburger Pils both use these.
There are two types of non-reusable closures (at least I consider them to be non-reusable). These are made of black plastic or rubber and a plastic tab. These are designed primarily to be used with the included gravity tap.
Turning the tab opens a valve which allows air into the keg to facilitate gravity dispensing. These closures are a craps-shoot, because there are two kinds which look very similar. The three-piece variety allows you to remove the plastic tab and then tap the keg much like the reusable bung. But there's another variety that's two piece and cannot be tapped because the black bung is solid. These bungs have to be completely removed and replaced with a Wecomatic bung in order to tap the keg. Yellow Snow had these last year, although Rogue told me they would look into changing that for this year's release.
Of course, we also have the non-reusable beertender kegs.
These aren't reusable. Don't buy unless you like Heineken or Newcastle and don't care about reusing the keg.
In addition, there are some variations on the reusable mini-keg.
Huber Packaging, GmbH makes a reusable mini-keg that also has a integrated CO2 cartridge. It's called easyKEG. I've only ever seen this in the U.S. holding Cuvee de Trolls. It's very expensive. These could be useful for re-use - if you drink the Cuvee de Trolls at home, and leave the built-in CO2 intact, you could use it later to dispense homebrew on-the-go without having to bring a CO2 bottle. Unlike the Beertender kegs, these are sealed with a bung and the CO2 cartridge is built into the top of the keg. There is a plastic tab on the top which is used to control the release of CO2 into the beer.
(Insert top-view photo of easyKEG)
There is also a variation of the mini-keg that does not have the integrated gravity tap. This would be ideal for homebrew, because it would clean up much more readily than the available ones. Sadly, I've never seen these in the US.
Dispensing from mini-kegs
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Most reusable mini-kegs include a gravity tap that you can pull out from the bottom. Ignore this unless you plan on drinking all ten pints in a few hours.
Also popular is the Party-Star tap that takes a CO2 cartridge and dispenses from a spout in a similar fashion to the Heineken mini-kegs. This is great for taking a MK to a party, but it's useless if you want to have a real draft system built around MKs.
If you scour the web, many people have compiled instructions for building a MK tap that connects to a draft system. Perhaps I am exceptionally bad at building things, but I wasted a lot of effort on buying and returning parts before I gave up on building my own. For not much more money than it takes in parts to build these, you can actually buy a pre-made device from a German company called Wecomatic. They are also the ones who manufacture the resuable bungs that you see on many off-the-shelf MKs as well as the homebrew models. The product is called the Flexi-Tap. I bought the 5/8" version with a 4mm nozzle (seals to 3/16" beer line with a tight clamp) and a 10mm nozzle (seals to 5/16" CO2 line). I got four of these to make the shipping from Germany worth my while, which does add a considerable expense to the system. Please note that if you buy this you might have to switch the nozzles around (I guess in Germany they use big beer lines and small gas lines). But, the system is for my office so I was able to expense it (YMMV) and I figure this is a one-time investment like faucets and hardware. Once you have the taps, you can just connect them up to the draft system like you would any other hose-barbed device. Later, I ditched the beer nozzle and installed valved quick-disconnects instead. I also installed a quick-disconnect on the gas side, but a cheaper non-valved one will server here due to the Flexi-Tap's built in check valve on the gas side.
(Insert photo of Flexi-Tap with QDs)
To tap a keg, just stab the dip tube into the white insert in the bung. The insert will drop into the keg. Continue pushing the dip tube all the way to the bottom of the keg and click the retention hooks onto the rim of the keg. That's all there is to it!
(Insert video of tapping mini-keg)
Sometimes you will get a little bubbling from the interface between dip tube and bung. Push down the tap some more and wiggle it a bit and this should seal it up.
Some off-the-shelf kegs of commercial beer have a different bung with a pull-tab to let in air (when using the gravity tap). Gently pull the tab off of the bung and there should be another piece underneath. This piece can be stabbed into the keg just like the white insert on the homebrew bungs. If you are unable to stab the bung, you might have one of the solid two-piece bungs. In that case, you have to remove the bung and replace it with a Wecomatic bung.
(Insert video of tapping 3-piece bung)
Force carbonating mini-kegs
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The main reason I wanted to get into kegging is that I hate bottle conditioning. I hate waiting, I hate the uncertainty and I've just had bad experiences with flat beer (oh, back in the closet for another couples of weeks I guess!). With a keg system, you can force carbonate your beer quickly, and mini-kegs are no exception! These things will easily take 20 PSI which is all you need to get your beer carbonated overnight.
All you need is an extra reusable bung (these are under a buck) and a 1/2" to 3/8" hose barb adapter (these are around a quarter at US plastics:
http://www.usplastic.com/catalog/item.aspx?itemid=23253&catid=465) for each mini-keg that you want to force carb.
(Insert video of mini-keg force carbonating)
1. Purge the mini-keg with CO2 and fill with COLD finished beer (I like to rack under CO2 using an orange carboy cap - it makes this incredibly easy with little to no O2 exposure)
2. Remove the white insert from one of your bungs and seat it in the keg opening
3. Attach the 3/8" end of the hose barb adapter to a gas line and connect to your system (make sure the gas is OFF!).
4. Plug the 1/2" end into the hole in the rubber bung. Jam it down in there.
5. Turn your reg all the way down and turn the gas on. Slowly increase the reg pressure to 13-14 PSI (depending how carbonated you want your beer) and make a note of the adjuster position at this pressure. Then slowly increase to around 20 PSI. The barb should stay sealed in the bung with no leakage. Verify this with some star-san spray.
6. Pick up each keg and shake it vigorously for 60 seconds. You will hear and feel the gas moving into the beer. The temperature of the keg will also feel like it is dropping significantly.
7. Turn the regulator adjustment screw back to the position for 13-14 PSI. The pressure gauge will not move because the kegs are already pressurized to 20 PSI. Shake each keg for a few more seconds and the gauge should drop. Verify a good seal again.
8. Leave them at 13-14 PSI overnight and in the morning you should have perfectly carbonated beer!
You can also set-and-forget at 13-14 PSI for a few weeks if that's what you prefer (or if you want to serve some kegs and carbonate others without a dual body regulator)
Once you're done carbonating, turn off the gas to the keg and pull out the adaptor. Quickly pull out the bung and replace it with a complete, sanitized two-piece bung (with the insert plugging the hole).
If you don't mind tying up one of your flexi-taps for a few days or a week, you can also just put the flexi-tap in there and carbonate using that, assuming your beer out has been valved.
Cleaning mini-kegs
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In theory, a good soak in PBW or OxyClean followed by a thorough rinse and sanitizer spray should be sufficient. But I find that a gentle scrub with a MK brush (available from most online HBSs for a couple bucks) is a must to get them really clean. I don't bother with the gravity spout at all (I wish I could get them without!), but if you have ever opened it then you should drain some cleaner and sanitizer through it to make sure there's no nasties hiding in there. I have heard you can even pull the entire spout assembly out and replace it with a second bung to make cleaning easier, but I haven't ever done that.
(Insert video of mini-keg cleaning)
Make sure you recover the insert from the mini-keg during cleaning. It usually falls out during rinsing, but if it doesn't it can be tricky to recover.
Other concerns
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Mini-kegs are tin-plated steel, not stainless. This means that if you don't treat them carefully, you could end up scratching off the tin plating and exposing the steel underneath. The steel will quickly rust if this happens. So be gentle.
(Insert photo of rusty scratches)
If you ruin a mini-keg, don't dispair. A free mini-keg is only ten pints of delicious Kostritzer away!
Make sure you ask your favorite local brewery if they are willing and legally able to fill a mini-keg with your favorite beer in growler fashion. Most will say no, but sometimes you'll strike gold.
