Foamy Heineken

[albertobob]

I have had a kegerator for over a year now and I am currently dealing with the most angry-ill tempered-foamy keg of Heineken I have had so far. I have had around twenty or so kegs since I put together my kegerator last fall. Here is the problem, when I pour a pint of beer I get about 80% foam. The condition of my kegerator is as fallows; the kegerator is at -1 degrees centigrade so about 29 degrees Fahrenheit. The reason for the low temperature is that something is wrong with the thermostat on my fridge and the next lowest temperature is about five and a half degrees centigrade or 42 degrees Fahrenheit which is well and above the standard three point three degrees C or 38 degrees F one wants to maintain. I am aware of the sensors that will automatically regulate the temperature of the fridge but I don't have the funds for one of those right now.
I have a 10lb CO2 tank with a dual regulator on it. The pressure to the keg is between twelve and fourteen PSI. The CO2 tank is fresh I have only had two other kegs draw from it. I have an in-line CO2 purifier between the regulator and the tap that I installed about two months ago new. I am using the proper tap, a S type tap for the keg of Heineken. It is a brand new tap I got from Micro Matic about a month ago. By the way I have had this keg for about three weeks and the whole time it has been at -1 degree C and 12 to 14 PSI. I cleaned my entire kegerator set up between my last keg (a keg of Sierra Nevada Brown Ale which worked perfectly I might add) and this keg of Heineken. I used the beer line cleaning powder sold by Micro Matic. I fallowed the cleaning directions and cleaned the faucet, tap, lines and shank completely. Letting them all soak in the cleaning solution for fifteen minutes. I rinsed throughly.
With the fridge being to cold the result to my understanding should be a more flat beer because at colder temperatures the CO2 has a high affinity to stay in the beer solution rather then dissolve out. This would increase the amount of carbonic acid in the beer and might make the beer seem more acidic. I am assuming one could refer to a study on this phenomenon. At the high temperature the CO2 dissolves out at a much higher rate resulting in foamy beer. I vaguely understand the relationship between temperature and pressure and the concentration of dissolved CO2 so I might be wrong. But it is to my understanding that the lower temperature should make the beer less bubbly and less foamy. As for the pressure I am not entirely sure what pressure I should be at. My elevation is about 40 ft above sea level. I am not aware of any equations to determine the proper pressure of the beer vs the outside pressure and temperature. If someone knows of such equations that would be really helpful.
Some other factors I had not mentioned before is my kegerator is in the form of an old stand up fridge with the faucet and shank built into the door. The fridge keeps the faucet around the same temperature as the fridge so the problem is not the beer getting warm as it is run from the keg to the faucet. Also my beer line is about five feet long with a difference between the tap on the keg and the hight of the faucet being about 8in.
The only thing I can think of that might be causing the beer to foam could be the lubricant used on the o-rings in the faucet. I may have not fully wiped the o-rings completely clean leaving a larger quantity of residual lubricant on the o-rings. I hadn't thought of this until now. I am using the food grade pump and probe lubricant sold by Micro Matic. Could the problem be related to an excess of this lubricant coming into contact with the beer. This is best guess, any ideas or comments would be greatly appreciated.

[lunkhead]

3 weeks at -1c. What is the beer temp? Does the beer come out the faucet clear or foamy? If clear than it must be foaming when it hits the glass. If the beer is too cold and your using 12-14 psi you may be over carbonating it. The cold beer hits the warm glass, foam?? There are charts out showing beer temp vs co2 pressure to maintain the correct volume of co2. Do a "volume of co2" search forum and you'll find links for it.

[albertobob]

From the advice of lunkhead I tracked down a table showing the volumes of CO2 dissolved into the beer I was able to firstly determine my beer is to cold as 29 degrees was not even on the chart and yes my beer is coming out of the faucet clear and foaming when it hits the glass. Yet warm glasses have never been a problem before.
From looking at the chart the relationship between temperature and pressure would seem to be linear in nature. From this observation I plotted out a best fit line for the for the volumes of CO2 at 29 degrees F for 12 to 14 PSI. I was able to determine this would put my volume of CO2 at somewhere between 3.1 and 3.3 volumes of CO2 in my keg. After a bit of further searching on the web I found that a German lager, granted Heineken is not German, should be kept at around 2.5 volumes of CO2. This mean I have almost one whole volume of CO2 in excess of what the concentration of CO2 should be. Does anyone know how to convert volumes of CO2 into grams of dissolved CO2 per mL beer? I need to track down a general chemistry book and get the equations.
Anyway I think I figured out that the pressure was to high. My solution was vent off the CO2 in the keg, I did have some worry about contamination, so I vented off the excess CO2 from where the CO2 line connects with the tap. CO2 is heavier then O2 and forms a protective blanket over the remaining beer in the keg. As I have not shaken up the keg I don't think the CO2 blanket has been disturbed. I let the keg vent for about three hours. This would mean that as the CO2 bubbled out of the beer it further developed the CO2 blanket. Basically I started to let the beer go flat. I couldn't think of a better method by which to do this. Alternatively if I just turned down the CO2 to eight and a half PSI and vented the CO2 in the air lines at the tap the extra CO2 dissolved in the beer would bubble out and raise the pressure until reaching equilibrium at some point slightly less then the original 14 PSI. Say for instance 13.7 PSI, so I could keep venting and waiting for the keg to again reach a new equilibrium point and continue with the stepping down process until the beer reached equilibrium at eight and a half PSI. This would undoubtedly take days if not a week. Also the seal I have for my airline to tap connection also functions as a one way valve.
I have roommates not to mention myself who want to drink sooner then that. Time is a factor, so it would seem I chose to instead risk some contamination of the beer and release a larger portion of dissolved CO2 all at once and then let the beer re carbonate at the proper pressure. Looking back on having done this, I might not do it again though, beer is a terrible thing to waste. I will have to see how the beer tastes over the next week. Any comments or suggestions on my process of remedying this problem would be greatly appreciated.

[lunkhead]

"The reason for the low temperature is that something is wrong with the thermostat on my fridge"

I'd start with this. If the fridge isn't too old you should be able to get parts.

[albertobob]

Well I have some good news. I pulled the faucet off the front of the kegerator and found that there was excess grease on it along with a lot of beer gunk. Which is strang because I cleaned the faucet before I put in the keg. Anyway, that and venting the extra pressure off of the keg and letting some of the CO2 vent out of the beer has solved my problem. I am pouring perfect pints again, with just the right amount of head. As for the thermostat issue my roommates threw in on one of those regulators that controls the tempature in the fridge. I don't have to worry about the broken thermostat now.