Hi, I'm Bjorn and this is Brewing TV.
Today we're going to talk about fermentation temperature control.
Probably the most important thing you can do to improve the final quality of your beer,
next to basic sanitation, is controlling your fermentation temperature.
Now, there's a few reasons why you may want to do this.
Maybe you live in a climate where during the winter time it's too cold to ferment, or during
the summer time it's too warm to ferment.
Keeping a stable temperature of your fermentation during those first few days of fermentation
is key to producing a good beer.
Or the other reason is that you're an ale brewer and you've decided you want to brew
lagers.
Lagers require much more precise temperature control to produce a good beer.
Ale yeast typically ferments at room temperature.
Lager strains much cooler than that; typically in the low 50s.
Now special strains like Belgian yeast won't produce their signature flavor unless you
keep it in a very narrow temperature range.
But there's more to it than maintaining the ambient temperature of your room.
You could place your beer in a room that's perfectly stable in temperature, and it might
be the ideal temperature, but what a lot of folks don't realize is that the process of
fermentation can actually heat up the wort.
You may have a room that's stable at 67F, but the wort itself is fermenting in the low
70s.
To keep temperatures down, simple methods like an ice bath or wrapping your fermenter
in wet towels can help.
The problem is you really don't have control over that, and unless you're constantly checking
your fermenter, you can't be sure that you're fermenting at the right temperature.
That's why it's best to have equipment that actually monitors the temperature of your
fermentation, and can turn on either a heating element or a fridge.
I would recommend a digital temperature controller such as this that allows you to dial in a
precise temperature, and when the temperature fluctuates, it'll either begin heating or
cooling depending on how you have the unit set up.
Placement of the temperature probe is key.
You want to make sure you're actually measuring the temperature of the vessel, and not just
the temperature of the ambient air.
There's a few different products that allow you to do that, such as a Stopper Thermowell
that actually goes down into the liquid and allows the probe to measure the temperature
of the liquid.
While other products exist, such as longer probes that will actually go down into the
liquid.
A low tech alternative is to simply tape the probe to the outside of the vessel.
This is something that I do myself, and you can simply insulate it with a few folded paper
towels.
The nice thing is if you have a fermentation that might be vigorous, and may produce a
blowoff, the temperature probe won't get in the way.
Cooling your fermenter requires a fridge or a chest freezer.
Mini fridges work great for single carboys, but if you have a larger bat size, or a conical
fermenter, you may need an upright fridge or a chest freezer.
The digital temperature controller must be set to cooling mode.
Plug the fridge into the controller, and plug the controller into your power source.
Set the digital temperature controller to the temperature you desire, and when the temperature
fluctuates beyond that, the unit will kick on, and turn on the fridge, bringing your
wort back down to temp.
Heating requires a special device of some sort.
Some people will use a space heater or even an incandescent lightbulb, but there are products
that are designed to be used with fermenters.
Some units wrap around the fermenter itself, and can actually be held in place with electrical
tape, where other units like this mat will sit under your fermenter.
The important thing is pick one that works with the type of fermenter you have.
Some are recommended for plastic, some are recommended for glass.
As with the fridge, you need to make sure your controller is set to the correct setting.
In this case, heating mode.
Plug the heater into the controller, the controller into the power source, and make sure your
probe is attached to the carboy.
When the temperature of your wort fluctuates from the set temperature, the unit will kick
on and turn on the heat for your fermenter.
A quick note on power: in either case, whether you're heating or cooling, you're using electrical
equipment around large vats of liquid.
I highly recommend using a GFCI adapter to supply power to your controller.
This is similar to the outlets you might find in your bathroom or your kitchen, but should
liquid ever come in contact with any of the electricity, the adapter will trip and prevent
you from being electrocuted.
Most digital controllers will have a setting called the differential or the hysteresis.
It may called something different on your particular unit.
What that is, is essentially the range of temperature that has to change before the
unit turns on.
Most units have a differential setting of 2F.
For example, if you're heating your fermenter and you have a set point of 67, a 2-degree
differential will cause the unit to not turn on until the temperature drops to 65.
At that point it will turn on and bring your fermenter back up to 67 before turning off.
I typically use a 2-degree setting myself.
Now that you have the ability to control fermentation temperature, you have complete mastery of
your fermentation.
There are many advanced techniques that are now open to you.
You can ferment lager beers and even perform a diacetyl rest.
Some folks even like to gradually ramp up the temperature over the first week of fermentation.
Like anything in home brewing, there's a lot of opinions on that, but part of the fun is
trying it out for yourself and getting to know your equipment.
Thanks for watching Brewing TV.
Cheers!