Over the last couple of months, I’ve been rethinking the way that I chill my wort on brew day. Is there a greener and more efficient way than using a conventional immersion chiller? Well, putting my brew kettle in the freezer seems like a great idea, but it wasn’t all that simple.
Using a freezer to chill wort is possible when done so at a lower temperature (below 160°F/71°C). Using a freezer to reach optimal pitching temperatures in summer is a viable option. Nevertheless, there are some risks in using a freezer for this task including damage to the unit itself.
However, there is a whole lot more to consider before you totally abandon your wort chiller and go down the freezer route, so let’s talk about some of the biggest questions I had.
Why use a freezer to cool wort?
There are a couple of main reasons I can think of why a brewer may turn to a freezer to cool their wort, water conservation and time.
I have to say that during the winter I tend to stay clear of any type of wort chiller set up just because I don’t want to waste any additional water if I can help it.
Luckily for me the temperature where I live dips just below the ideal pitching temperature in winter, so I can get my wort cooled without using a wort chiller. In summer, however, this isn’t the case and I either have to use a chiller or another cooling device, or both.
If you have become conscious of how much water cooling wort actually takes and want to find an alternative way, then check out my articles on cooling wort overnight and how to avoid water wastage when using a wort chiller.
Another reason that someone might think about using a freezer to cool their wort is because it’s very cold and they think that it can cool down their wort very quickly. In some cases this is true, but it’s not going to happen as quickly as you may think.
When to put wort in a freezer?
Basically, don’t just terminate the boil and wack the brew kettle into your freezer, this isn’t going to turn out well for you at all.
Ideally, you should allow your wort to cool down from 212°F (100°C) to a range of 160-80°F (71-27°C) as this is when the danger of bacterial infection starts to rise.
Below, about 160°F (71°C) you will experience a lot fewer of the technical problems associated with putting your wort in the freezer, at 80°F (27°C) even less.
You can either rack your wort into your fermenting vessel and allow it to cool naturally while stirring it, or use an immersion cooler to reduce the temperature more rapidly.
Obviously, if you are trying to eliminate a wort chiller, then cooling naturally is the best option. Also, if you are using a plastic fermentation vessel, don’t transfer hot wort directly into it as chemical leaching is a real possibility!
Are there any dangers to using a freezer for chilling?
There are absolutely no physical dangers that I could find in terms of your health or the ‘health’ of your wort. However, putting boiling liquids into freezers can have some adverse effects.
- Defrosting – basically using boiling water is an excellent way to defrost a freezer, so if you are using anything other than a chest freezer, you may have a flood on your hands. This being said, eventually, the freezer would reduce the temperature of the internal chamber back down to 32°F (0°C).
- Compressor failure – as your freezer compressor will be working overtime to help return the internal temperature back down to the freezing point, it could become overloaded and actually break.
- More energy usage – as the temperature is raised above the optimal levels for your freezer it’ll take more energy to reduce it again. This is going to show up in your electricity bills and is a point against this method in the ecological department.
- Melting – If you place a boiling hot brew kettle on some plastics used in some freezers you may find that it just melts, which is going to piss your wife off to no end!
- Frozen wort – Another danger, but hopefully less likely is the risk of forgetting about your wort and allowing it to fully freeze. Although this won’t really harm your wort, it would add significant time to your brew day as you wait for it to melt and rise to pitching temperature.
How long does it take to cool wort down in a freezer?
To answer this question you need to know so many factors that I can’t be more accurate than a range, from 90 to 20 minutes. This is because you need to account for the ambient temperature and cooling coefficient.
You can use Newton’s Law of cooling here, but it will make your head spin, to be honest!
If you take into account that introducing a very hot liquid into the freezer will initially raise the internal temperature, it’s clear that boiling wort will take longer to cool.
Although there is a phenomenon known as the Mpemba Effect which shows that under some conditions hot water can freeze faster than cold water, there are many things to take into consideration.
Firstly, as I’ve mentioned, the starting temperature of the wort and it’s influence on the ambient temperature of the freezer will affect the cooling time.
Also, the amount of wort you are trying to cool down is significant. Smaller quantities of liquid seem to cool or freeze, faster than larger quantities. So using this freezer method on a partial boil may be more effective than a full 5 or 10-gallon batch.
What temperature to set the freezer at?
To get the most out of your freezer when cooling wort at any point it should be set to the optimal temperature.
The FDA recommends that freezers be kept at 0°F (-18°C) to ensure proper storage of food, and so if using a conventional freezer to cool wort you should do the same.
Obviously, if you are using a converted freezer as a keezer, for example, you will have changed the settings to avoid freezing your beer, so just take this into consideration.
Using ice to chill wort
If you have read this far and decided that perhaps using a freezer isn’t for you, then what about using ice instead?
Putting your brew kettle in an ice bath in your sink or bath is a really effective way to reduce its temperature, especially if you don’t have access to a wort chiller or choose not to use one.
You can also if done in the right way, use ice directly in your wort to reduce its temperature significantly. If you want to learn more about using ice to cool your wort down more quickly, then check out my full article here.
How much freezer space do you need?
If you want to use this technique, even just to reduce your wort down by a few degrees during a hot summer brew day, you’ll need adequate space.
The more cold air around your brew kettle or fermenter the better, so a minimum of about 1273.173 sq in (8214.0029268 cm2) for the average-size brew kettle is needed.
In all honesty, the best type of freezer for this job are the larger ones, such as chest freezers.
What are the best types of freezers for brewers?
If you can get your hands on a conventional chest freezer, this should give you the space and a cooling coefficient that you need to help you reduce the temperature of your wort in summer.
If you can’t use the family freezer, then why not treat yourself to a dedicated wort cooler, check out this model on Amazon. Make sure you check the dimensions of your kit before purchasing anything though.
Perhaps the best option would be to invest in a keezer which you can use for multiple tasks, helping with cooling your wort and later keeping your kegs chilled. You can make your own from a used chest freezer or just buy a dedicated unit. Check out this inexpensive model on Amazon
In addition to a chest freezer, you should consider investing in a temperature control unit, and the inkbird brand is trusted worldwide. This will help make sure that you don’t cool your wort too much. See this model on Amazon and get one for yourself.
After going through this process in detail I think it’s safe to say that chilling wort with a freezer is one step in the process and perhaps isn’t the only solution.
In summer it will certainly give you that extra helping hand to get down to the ideal pitching temperature, however, the extra power usage and risks to the freezer compressor mean that chilling a boiling hot wort isn’t a viable option.