Fermentation Temperature Control (Updated!)

(Updated 6/2014!)

I thought I'd break out of my recent beer review mode and get back to homebrewing (mainly because I finally got a chance to brew again the other day.)  I brewed up a second version of my award winning English barleywine, coming in at 1.104 starting gravity, and realized I'd need to work hard on getting the fermentation temperatures just right on it. 

Over the years I have found that recipe means less than fermentation control when it comes down to making a great beer.  There are lots of ways to get better control of your fermentation and I'll go over a few of them today.  First off some helpful hints. 

1) Most yeast put out fruity esters and higher fusel (paint-thinner) alcohols at higher temps, so keeping the beer in cooler temps will help retard that process.  Some beers benefit from those esters--take German Hefeweizen and some of the Belgian ales, so pay attention to your desired goal and the specifications of the individual yeast.  All of the yeast companies publish the optimal temperature ranges for all their strains on-line, so check that out before making any big decisions.

2) Fermentation is an exothermic process, meaning that those madly active yeast are putting off heat as they get going.  Factor this in with your plans for temp control.  Ideally I will start the wort at the lower end of the temp range I'm looking for and let the yeast activity ramp it up naturally.  This can cut down on the esters as well. 

3) Flocculation of yeast can be a factor.  Some yeasts flocculate (fall out of suspension) easily like many of the English strains, and do so easier when cold.  This can cause the beer to be under attenuated and too sweet.  Other yeasts like Belgian Saison stay in suspension almost too well and need a pretty high temp to stay active and finish the fermentation process.  I'll actually ramp the temp on those up slowly over a week or so to make sure they finish out. 

4) Keeping track of carboy temperatures can be difficult.  All of my carboys have one of those temp strips on the outside of them, but they are not the most accurate things in the world.  Inserting a floating thermometer into the wort will get you a decent temp, but every time you do it you risk infection of your beer.  For a bit more cash you can get a stainless steel thermo-well inserted into a rubber bung, then insert a temp probe into that--maintaining relative sterility.  Unfortunately the thermo-well does not work well when you are using a large blow-off tube (during the most critical time of fermentation.)

Cooling:

Most homebrewers tend to err on the side of too warm for their fermentations.  If you start with an average room temp of 68-70 degrees, then your fermentation runs the temp up a couple more degrees this will put most yeast in the upper end of their desired temp range.  In general, anything over 70 will likely result in some ester formation.  Keeping your wort cool is of paramount importance for creating the best possible beer.  There are many techniques for doing this.

1) Map out your home's temperature zones.  This has been my primary technique for years.  Take a thermometer and find your home's warm and cool spots.  My laundry room closet stays a pretty constant 68 degrees year round.  My basement is usually around 64 degrees, and if a carboy is directly on the cold tile it can drop to 62-63.  Keep in mind weather changes, as well as using home heaters or air conditioners, can change these measurements.  I have been known to start my fermentations in the basement on the floor, then drag the carboy upstairs into the closet to finish up once the main fermentation is slowing.  This does require man-hauling carboys around and can be dangerous (especially with three cats who like to trip people on the stairs...)  This method also may be difficult if one does not have a supportive spouse who allows carboys all over the home.  I'm lucky on this front, but even Sj reaches her limit sometimes.  Also if you are using a closet for this method, use a blow-off tube!  If you explode foamy beer and yeast sludge all over your wife's clothing you will either risk bodily harm, or possibly have to change hobbies.

2) Wet T-Shirt!  Not the kind you are hoping for.  One method I've tried is setting a carboy in a shallow water-filled tub and wrapping it with a wet t-shirt.  The wicking of water up the shirt and into the surrounding air acts to cool the surface of the carboy a few degrees.  Aiming a fan at it will increase the effect.  The downside to this method is that monitoring temps is tougher and results will vary depending on the humidity in the home.  Also it is a pain.  I did not have much success with this--the shirt dried up and the cats enjoyed cavorting in the water.

Big water tub and blow off tube!

3) Big water tub.  This is my newest attempt at control, and I'm trying it out for the first time on my barleywine.  The idea here is that the carboy rests in a large tub of water, acting as a heat sink.  Rather than only bumping up the temp of 5 gallons of wort, the heat of fermentation will also need to raise the temp of the surrounding 4-5 gallons of water, making for a slower and lower overall temperature rise.  I discovered that my temp strips are placed too low on the carboy and will likely be submerged if using more than 4 gallons of water...I'll have to see if this is enough to work.  The ambient temp in the basement is about 64 degrees, so this should help out with control.  If the wort is still too warm, you can actually add ice to the water if needed. 
{Addendum: Yup this worked great!  I've done it on two beers now and found I only needed 3-4 gallons of water at that ambient temp to keep tight control.}

4) Insulated cooler.  At NHC 2014 I observed the Cool Brewing fermentation cooler at work.  This is basically a large soft sided thermal cooler that your entire carboy or bucket fits into.  By adding 2 liter soda bottles or 1 gallon water jugs filled with ice, you can drop the fermentation temp in the bag by several degrees.  They actually had it hooked up with a digital thermometer showing external temp of 72 and internal temp of 50 degrees there.  These run about $57, so aren't cheep but are a step up from a big bucket and not as expensive, nor as space-occupying as a lager fridge. 

5) BrewJacket.  This is a new contraption that I saw on display at the NHC 2014 in Grand Rapids.  I have no idea if it works as advertised and would love feedback if anyone has used one!  This is a device that actually inserts a tube into the beer and pumps heat out of the beer, supposedly cooling it to 35 degrees below ambient temp.  They do also sell an insulated wrap for the carboy to make this more efficient.  This was a Kickstarter that completed funding and is up for pre-orders now. 

6) Lager fridge.  This the ideal set-up for temp control.  I have an old fridge out in the garage hooked up to a temperature controller which keeps the temp within 1-2 degrees of desired.  The temp probe will measure ambient temp in the fridge though, and not the internal temp of the carboy.  In that first few days of active fermentation you will need to keep a close eye on this, decreasing the set temp to below where you want it.  You can tape the probe to the side of the carboy surrounded by some insulating foam: that will improve results, but tape doesn't stick on moist, cold glass very well.  If you have a better/more modern controller that will fit a thermo-well, this will give the very best result. 

A well decorated lager fridge!

7) Walk-in fridge, fermentation room, glycol jacketed conical fermentor.  These are all the holy grail of fermentation, but probably excessive (rubs hands together evilly).

Heating:

Sometimes you need heat added to your brew.  For instance: when my actively fermenting barleywine starts to slow down and temperature drops below the ideal range for the English yeast.  If I don't get that out of the cool water bath and either upstairs to warmer climes or add some other form of heat, that yeast is going to crash out before fermentation is done, leaving me with a cloyingly sweet under-attenuated beer.

1) Moving it.  Back to knowing the warm and cold spots in your house, ideally areas that are fairly stable. 

2) Fermwrap or Brewbelt.  I've used a brewbelt before, but the instructions tell you not to use them on glass, so I only tried it on a plastic bucket.  From talking with my friend Tim Roets, he has had bad luck with those, going through three of them.  More recently I've used a Fermwrap and love it!  Wrapped around the carboy and secured with electrical tape, this has to be used with a thermowell to keep the internal temp of the carboy constant.  It does a great job of heating--keeping you right where you want the beer, within about one degree.  I usually use this set-up once I no longer need a blow-off tube and the high krausen is dropping on my beer.  You want to start the heat before the temp of your beer really starts dropping.  I will often slowly ramp up the temp over a few days to make sure I get a full fermentation.  Most of the wacky flavors from hotter temps happen in that first few days, so getting to 72 at the tail end of fermentation shouldn't cause too much trouble. 

The Fermwrap in action, regulated by a digital temp controller inside a thermowell

3) Heat lamps.  I've read about crazy people hook light bulbs or heat lamps up to warm their beer, but have no personal experience with this.  Make sure the beer itself is protected from the light--that can potentially cause skunking.

These are the major ways in which homebrewers control temps, many of which I've tried with varying levels of success.  What have you tried?  Do you know of any other cool techniques that should be added?