Brewing

Foam Sucks

If you have one keg or many, chances are high you’ve had to deal with foam. When we say ‘foam sucks’ we really mean ‘too much foam‘ sucks. After all, a solid foam head on a well-poured beer is a beautiful thing. Europeans appreciate this and hopefully we’ll get there in America (please be patient with us, we’re still trying to figure out that metric thing).

Good Foam – Bad Foam

Foam sucks when it’s the majority of what comes out of your tap. If your glass looks like a Starbucks Frappuchino, you’ve got problems. These are solvable problems, but not always easy. Whether you have a basic kegerator or prepping to upgrade your multi-tap rig with Kegtron keg monitors (which you really should – it will be way cool) you will be much happier with taps that don’t spray foam like a fire extinguisher.

Let’s dig in!

Quick Fix

Do not read this section. Skip it! There’s no such thing as a quick fix. You’re letting the foam win!

If you won’t listen and are one of those people who search for video games cheat codes, here you go:

  • Set fridge to 38°F (3.3°C)
  • Set regulator to 11psi (0.8bar)
  • Use 7′ (2.1m) of 3/16″ (4.76mm) I.D. draft line tubing

We won’t even give an explanation here since you cheated (again). To redeem yourself, keep on reading…

When Foam Attacks: Causes & Cures

The potential sources of foam attacks are many. Chances are you’ve already know some of this intuitively or through trial & error . What’s not obvious are the most likely causes of excessive foam. So here’s our view of the culprits ranked from most heinous to minor offenders:

1. Unbalanced Draft Lines

Like bipolar crazies on public transit, unbalanced draft lines will drive you crazy and need treatment right away. The single most important factor in a good pour is balancing the serving pressure with the resistance of the serving lines. If your pressure exceeds the line resistance then dissolved CO2 will escape from the beer before it hits the tap. This is a one-way ticket to Foam City.

Serving pressure is pretty self-explanatory. If your regulator is functional and reasonably accurate, you serving pressure is the same as your gauge. The one exception is if when you turn-down your regulator: your gauge may be out of whack until you release excess pressure from your keg.

Line resistance is a little more complicated as it is a function of your line length, inner line diameter, tubing type and vertical rise between your keg & tap. Calculating this resistance requires a little math or a handy web calculator (see below).

OK, that was all background info – now for the real work:

  1. Decide on your desired keg temperature and carbonation level (expressed in volumes of CO2)
  2. Look up the proper pressure for your target temp & carb level
  3. Calculate the line length for your serving pressure. How? Mike Soltys’s calculator, that’s how! He did the math so you don’t have to. If you ever meet this guy, make sure you buy him a beer.
A few more pro tips:
  •  In the calculator above, use a flow rate of 8 seconds per US pint (8.5 sec per 0.5L) which is the norm for bars
  • Use 3/16″(4.76mm) I.D. tubing! This has a huge impact on line resistance – only go bigger if you have an very, very long run between your keg and your tap. Ditch that 1/4″ tubing!
  • Is your line length too long? Don’t trust the calculators? A great option is to use a flow control faucet (see below) so you can dial in the resistance on the fly.
  • There are many different formulas for beer line balancing on the web and most don’t agree. When it doubt, go longer! Worst case, your beer pours a bit slower but it’s easy to shorten a line. Go too short and things get foamy fast without a quick fix.

Once again (with feeling): Balance those lines! It’s the single best thing you can do to tame the foam.

2. Keg Temperature

Anyone who has been pouring for a while knows this intuitively –  ice cold beer pours easier than warm beer. Why? Science! The colder the liquid, the more CO2 can remain dissolved in the liquid. As beer warms, the dissolved CO2 breaks out of suspension in the form of bubbles -> foam.

This is precisely why most bars serve draft beer cold: 38°F / 3°C is typical. Colder beer means less foam, less waste and faster pours. Good for the barkeep but not necessarily optimal if you want to taste your beer (fuel for a future post).

As a kegerator/keezer owner you kneed to know the temperature of your kegs. Don’t trust your thermostat reading! Get a quality thermometer and tape it to your keg and let it sit for a a solid 10-20 mins and take a reading, you may be surprised. Now make sure you are hitting your target temp by using a quality external thermostat  if your rig doesn’t have a digital one built in. If you make an adjustment, let things sit overnight before taking another measurement. Beer kegs have a huge amount of thermal mass which means it will take many hours for a thermostat change to take effect.

Remember, you can serve beer above cold-ass bar temps without foaming but be aware that the warmer the beer, the less margin for error. When in doubt, start cold (e.g. 38°F/3°C) and follow the remaining steps outlined here. Once things are pouring nicely, you can edge up the serving temp to more flavor-respecting temperatures.

3. Draft Line Temperature

Experiencing hot flashes? Check your medication then check your first pour. If your initial drink is foamy but subsequent pours are just fine, chances are high your draft lines are warm. This is especially problematic for kegerator towers and DIY keezers with collars. Read about how to fix each below.

Like keg temperatures, the same rules about warm beer apply to draft lines. Keep your lines at or near the same temp as your kegs and your pours will improve.

4. Over Carbonation

OK, let’s assume you’re a diligent student of the Kegtron School of Foam Control, you’ve complete courses #1-3 above and your tap is still foaming like a mad dog? The next thing to check is your carbonation level. If your beer is over carbonated, even a rig that is otherwise dialed-in will foam. Fortunately this is a solvable problem: adjust your CO2 pressure.

Before you can fix things, you need to know your target carbonation levels. Carbonation levels are specified in volumes of CO2. The most common carbonation level is 2.5 volumes for mass-market ales and lagers. Different styles will be lower (e.g. British ales) or higher (e.g. German wheat beers and some Belgian styles).

With your target in-hand, use a handy calculator to figure out the proper regulator pressure for your target and fridge temp. If the pressure is too high, you’ll have over-carbonated beer. Too low and your beer will eventually go flat.

Pass Some Gas

If you think you’re keg is over-carbonated, there are two options:

The slow method
  1. Adjust your regulator to the new target pressure
  2. Turn off your regulator
  3. Use the gas relief valve on your keg to vent CO2 pressure
  4. Turn your regulator back on
  5. Wait a few hours
  6. Repeat steps 2-5 at least 4-5 times. Yes, it’s a pain, but it works!

 

 The fast method
  1. Depressurize the keg
  2. Apply gas into the “OUT” fitting on your keg for just a second
  3. Slowly release gas from the keg lid pressure relief valve (release too fast and it will be a foamy mess)
  4. Repeat steps 2-3 about 3-4 times

This method forces CO2 through the dip tube at the bottom of the keg. As it bubbles up it agitates the beer and creates nucleation sites for the dissolved CO2. This causes the CO2 to break out of suspension and reduces the carbonation level of the beer. Brilliant.

Read more about this method here.

Partial Keg Foam

Ever had a keg that poured fine for a while but became foamy as the keg emptied? Over-carbonation! If your fridge is cold at the bottom and warmer at the top (i.e. a temperature gradient) the average beer temp will gradually drop as you drain the keg. The lower temp leads to increased CO2 absorption. The increased head space of the emptying keg also makes it easier for CO2 to be absorbed by the beer.

The solution here is the same as above: Follow the steps above to lower the carbonation level and make sure the temperature levels are even throughout your fridge (e.g. use a circulating fan).

5. Under Carbonation

The opposite of #4, under-carbonation can also cause foaming. Is this your issue? The telltale sign is bubbles or air pockets in your beer line.

A sure sign of under carbonation

Fortunately, the cure is easier than over-carbonation: increase your your serving pressure so it is balanced as described in #1. You’ll likely need to push a few beers through your lines after the pressure has equalized.

6. Pilot Error

While it’s easy to curse inanimate objects for our pouring woes, the fact is some people simply don’t know how to properly serve a beer. Of course not you, gentle reader, but maybe your friends and family :).

Biggest Serving Fails
  • Partially opening the tap (usually by a scared, first-time server). Always open the faucet full-throttle.
  • Not tipping the glass.  If you’re setup is less-than-perfect then pouring down the side of the glass will help a bit until you get things dialed in.
  • Frozen glasses. Seriously, are you still using this bar gimmick? We hope not. Ice on the side of a glass creates nucleation sites which create foam. The extra cold glass also erases beer flavor (which usually isn’t the goal, except in certain parts of the US).

7. Your Beer is Out of Style

Unfortunately there are some styles that simply are really hard to serve from a tap without excessive foam. Hefeweizen: I’m looking at you. Wheat beers have higher protein content vs. typical beers. This gives it a fantastic fluffy head but also means you’re going to get more foam when pouring. If you serve at the proper carbonation level of 3.3-4.5 volumes of CO2 it makes things even harder.

Is there a great solution here? Maybe not, but here are some ideas:

  • Use a flow-control faucet to restrict the flow rate. It will take longer to pour, but is effective.
  • Be patient!  Pour a partial glass, wait, pour some more. Pouring a wheat beer from a bottle requires this method, so it’s legit.
  • Intentionally under-carbonate your wheat beers at more conventional level. This is Bavarian blasphemy, but an option if your drinkers don’t know any better.

8. Take a Leak

If you see beer dripping from a line or fitting the problem is pretty clear. Not only are you making a mess wasting beer(!), it may also be a sign that air is getting sucked into the line and creating foam.  Not good, but fixable with a plumbing tune up. If your tubing connections are loose, replace your lines and/or add hose clamps. If you have corny kegs, consider replacing your O-rings.

9. Clogged Fittings

An AARP meeting isn’t the only place to find clogged plumbing. If you’re a homebrewer that dry-hops in the keg, this is a very real concern. Hop debris can and will get stuck in your keg fittings and/or faucets if you’re not careful. Whatever crazy things you add to your keg, make sure you have some form of filter in place to keep the chunks out of your lines.

Another gross but real threat is…. insects! If you have a kegerator in the garage use faucet covers to keep those nasty critters out of your taps.

10. You’re a Dirty, Nasty Line

In theory, dirty lines can cause foaming, but chances are you most likely have something else at work. This doesn’t mean you’re off the hook when it comes to cleaning your lines. Do it! It will make your beer taste better and will keep out the green funk – just don’t expect a flush of cleaning solution will magically solve your foam problems.

A more legit beer line concern is the accumulation of mineral deposits within the lines, shanks and faucets. This is known as “beer stone” and can be difficult to remove. If caustic beer line cleaner doesn’t remove it, it may be time to replace your lines.

Equipment Specifics

Now that we’ve summarized the 10 Foamy Sins, let’s take a look at some equipment-specific concerns and fixes:

Faucets

One of the best ways to trick out your kegerator, keezer or jockeybox is… Kegtron! Wait, that wasn’t very subtle. Besides Kegtron, one of your best upgrades is a flow-control faucet. While slightly more expensive than a generic tap, a flow control faucet allows you to adjust your line resistance on the fly. This is magical for several reasons:

  • Dialing back the flow is equivalent to adding length to your draft lines. If your calculations don’t quite work or your prefer short lines, flow control is a beautiful thing. Adjust the flow as you pour your tap is balanced.
  • Like to change things up and serve at different pressures? Variable flow control makes it easy without changing your lines.
  • Can’t fix that first-foamy-pour? Dial back the flow for the first glass then throttle up for the next pours.

There are several vendors with flow-control faucets. Check out CMBecker, Intertap, and Perlick for some quality offerings. Want to keep your existing standard faucets but still adjust the flow? Try an inline flow control device mounted within your cooler.

Kegerators

When we’re talking about a kegerator, we’re referring to a standard kitchen refrigerator that has been converted to a beer fridge OR a purpose-built refrigerator intended specifically for kegs. Either way, kegerators are great since almost all of the interior space is surrounded by cooling coils and there are less likely to be warm and cold spots. If your tap is mounted on the door, you’ve got a great setup where the kegs and lines are going to be held at the same temp.

Is your kegerator smokin’ hot?

Having said that, many (if not most) kegerators use a draft tower to hold the faucet tap(s). This is where extra attention is needed: Since heat rises, draft towers can collect warm air and the beer lines within will warm up. This leads to the first-foamy-pour symptom.

The most straight-forward fix is a tower fan. Search the web and you’ll find numerous options to blow cold air up into your  tower. This may not be fool-proof solution, but it is a big improvement over an uncooled tower. More exotic approaches use recirculating coolant lines to keep the tower cool. You can also find neoprene tower covers to externally insulate the tower.

Whatever approach you take, your goal should be to keep the draft lines at or near the same temp as the keg.

Keezers

If you’ve converted a chest freezer into a beer-serving fridge, you’ve got a keezer. Since all keezers are DIY projects, these can take many forms. If you’ve mounted towers on the keezer lid, the kegerator commentary above applies here.

Most keezers go for the “collar” approach whereby a four-sided wooden box is placed in between the freezer walls and the lid. This is really convenient since you can drill holes for taps anywhere without hitting coolant lines (a real buzz-kill, don’t try it). The downside to a collar is that you are pretty much guaranteed to have a layer of warm air sitting at the same level as your draft lines and faucets. Not only does this mean foamy first pours, but chances are some of your kegs are warm at the top as well. Not a good combo.

Fortunately the fix is pretty easy: a recirculating fan. Have a fan constantly blowing inside the keezer will minimize the temperature difference inside and solve numerous problems at once. Choose your fan placement carefully since you want to ensure good overall circulation and bottom-to-top airflow. If you have two thermometers, place one down low and one up in the collar region to see how close you can keep the temperatures.

Jockey Boxes

A jockey box is typically a converted camping cooler with a tap on the outside and ice-covered cooling coils (or cold plates) on the inside. Jockey boxes are great to serve kegs on the go, but they don’t always behave like your kegerator.

In a kegerator or keezer, the draft lines are almost always vinyl tubing, but jockey boxes need metal coils (usually stainless steel) or coldplates to cool the warm beer down to serving temperatures. Plastic and stainless steel have very different resistances: for example, 5/16″ O.D. stainless steel beverage line has only 18% of the resistance compared to the equivalent length of 3/16″ I.D. plastic beverage line. To put this in perspective, if you normally need 7′ of plastic tubing, you’d need 39′ of stainless tubing to achieve the same line resistance!

But wait, it gets more complicated: When serving from a jockey box you’re almost always outside and you probably can’t control the temperature of your keg. If it’s a nice 77°F/15°C day, the carbonation calculators would tell you to set your regulator to 33psi/2.3bar! Your common sense alarm should be kicking in right about now.

Here’s where you need to step away from the math: In a jockey box setting you’re probably not worried about the beer going flat over the course of a few hours. Ignore the carbonation tables and dial back the pressure until it matches the line resistance of your setup. It may take some trial and error to get it just right. If you want to throw some math at it, check out this article with different resistance values for different line types.

Picnic Taps

We couldn’t finish without giving props to the ubiquitous picnic tap (aka “cobra” tap).  By most accounts, this is the biggest foam-breathing monster of them all. Why? The same 10 Foamy Sins still apply, especially these:

  • Line Length – You still need to balance the pressure with the line resistance, but for whatever reason picnic taps are almost always paired with short lines.
  • Line Temp – If you have a handheld spigot, chances are the beer lines aren’t cold
  • Pilot Error – More often than not, picnic tap operators are not skilled technicians. They need to be taught to open it up full throttle. If you have a hand pump, it gets even worse as tap amateurs feel compelled to pump the handle with every pour. Not a recipe for success.
Typical picnic tap operator

All is not lost – it is possible to balance picnic tap lines (when in doubt, go long) and you can train keg monkeys how to operate a tap (while they’re sober). Have a few extra bucks to spare? Try a flow-control party faucet and dial in your line resistance on the fly!

 

Mopping Up

After all this trash talk about the evils of foam, remember that foam really is our friend! It’s part of what makes beer a beer. Learn how to tame the 10 Foamy Sins and you can enjoy foam once again. If you can’t, remember that wine never foams…

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