• KeggingAndCarbonation

Home Brew - Kegging and Carbonation

Of course the most important thing about a keg is how to empty it ... one glass at a time.

Kegging beer for the first time is like trying to give a 200kg gorilla a swing while you are blind folded.

The links below provide some charts and information about the interaction of CO2, beer (approximated by water) and tubing. At the end of the day don't get too hung up on the numbers, if you understand the basics, then commonsense and taste buds will guide you. Some things to consider:

• Colder beer dissolves more CO2 (quite a bit more).

• CO2 takes time to dissolve in beer. The pressure you measure now might not be the pressure you read later. If you can't make sense of what is happening then maybe your beer has not reached equilibrium - you urgently need to send me samples for analysis

• Shaking the keg under pressure speeds up the dissolving of CO2.
• When your keg is full of beer (ie there is not much headspace), the pressure changes quickly as you draw off beer.
• Longer, thinner serving tubes slow down the pouring rate and can help when there is excessive foaming due to the beer coming out too fast.

• The pressure you read on your regulator *may* not be the pressure in the keg (eg if you have a check valve) more info.

• Every brewer has their own opinion and methods on this topic, including me.
• If it is your first time, everything is a bit mysterious, you will soon get the feel of it.

Crash Carbonation

The way I carbonate my kegs involves:

• Purging the headspace of oxygen. Insert CO2 and release multiple times.

• Beer at around 5°C or so (temperature has a major effect on CO2 solubility). I have also used this technique at warmer temperatures - you just need to make adjustments.

• Connecting CO2 at 400kPa or thereabouts.
• Lots of keg shaking. I don't bother counting. My gauge tells me what pressure is in the keg and watching this dip when you shake and recover when you stop gives an idea of how you are progressing.
• A few hours later I will check the carbonation and make adjustments as necessary.

I don't leave my CO2 line attached to kegs permanently, many fine brewers do. Because of this, particularly when keg headspace is low, a shot of CO2 is required every now and then at serving pressure.

Links and Resources

• Forced Carbonation I had some trouble with my beer being all head. This page has some clues. I converted this table to SI units.

• Beerlines How to calculate the dynamics of your beer lines. Size does matter. Popup Warning for this site.

• Draft Beer Balance Reference

• Carbonating at Home with Improvised Equipment and Soda Fountains

• Thermophysical Properties of Fluid Systems

• Bodensatz Keg Page details on using soda kegs for homebrew. Cleaning, refurbishing, filling and dispensing.

• Valpar Flexmaster tubing

• Valpar Brewmaster tubing

• Nylex BEVA tubing

• Purple Pig Can supply BEVA tubing and other useful bits and pieces.

Pat Casey posted this on craftbrewer.org "At a flow of 4.5 litres of beer per minute 4mm ID lines have a resistance of 42 kPa per metre, 5mm about 33 kPa, 6 mm 23 kPa, 8mm 8kPa and 10 mm 2.5 kPa."

Foaming Beer

There are a number of factors that can cause your beer to come out of the tap foamy. This list might not cover all of them but things to check:

1. Obstructions in the beer flow path, including:
   1. Beer gun/tap clogged or not opening fully.
   2. Incorrect poppets in the keg.
   3. Beer tubing kinked.
   4. Beer tubing with rough inside surface. Use beverage grade tubing.
2. Beer flowing too fast
   1. Too much pressure in the keg.
   2. Beer serving line not providing sufficient resistance to flow (ie too short or large inside diameter).
   3. Serving point way below the level of beer in keg.
3. Over carbonated beer. Even when you release the pressure from the headspace of the keg, the beer doesn't immediately go flat (same as opening a bottle).
4. Glass warm.
5. Cold beer passing through warm tap.
6. Poor pouring technique.
7. Style of beer.
8. Beer that has been sitting in the serving line tends to foam. This is where some compromise on beer line length comes into it.

Measuring the Keg Headspace Pressure

After some debate on rec.crafts.brewing about measuring the "true" pressure in the headspace of a keg, I decided to contact the manufacturer of my regulator, a Gas Arc R39.

Wayne Molloy's¹ response was:

1. "The outlet pressure on the regulator will only reduce if the gas is somehow released from the system down stream of the low pressure side of the regulator, it will not self vent if you turn down the outlet pressure with no gas flowing out of the system."

2. "The outlet pressure gauge will show you the pressure coming out of the low pressure side of the regulator, remember the pressure should be set with the gas flowing (working pressure) as the pressure will increase when the gas stops flowing (static pressure). If the keg is close to the regulator (within a few metres) you should get a reasonable idea of the pressure, if the keg is further away you will start to get pressure drop in the line, depending on how accurate you need to set the pressure this should not be an issue."

Some things to bear in mind:

1. If you have a check valve to prevent beer from accidentally flowing back into your regulator (what a waste of beer that would be) then a pressure increase in the keg headspace would not be indicated on your regulator gauge.
2. Some regulators vent excess pressure. That means if you turn down the pressure on the regulator so it vents, you will also be venting the pressure in your headspace (assuming no check valve). With my setup, I use the pressure relief valve on the keg.

paul sorenson