Controlling Fermentation Temperatures

If you look up any list of the top ten homebrewing errors, number one is always (seriously – always!) about cleanliness and sterilisation of your brew gear. However, not far after it you’ll find something about controlling your fermentation temperature.

This is primarily due to the fact that yeast operate best within a fairly limited range, usually just a few degrees. Below this they will become dormant and fail to properly ferment the malt sugars, above they become hyperactive, producing excessive fusel alcohols and diacetyl which can cause undesirable flavours in the final beer.

The optimum temperature varies considerably for each strain of yeast, with ale yeasts generally performing best between 18 C and 24 C, while lager yeasts tend to prefer much cooler temperatures, from around 7 C to 13 C.

So how can you control the temperature of your fermentation? The good news is that a number of techniques from the relatively inexpensive low-tech through to more involved methods are readily available.

For keeping your beer cool in summer, fermenters can either be half submerged in a bath of water – a technique recommended by John Palmer in his excellent How To Brew.

Alternatively, if you don’t have a spare bath lying around, then setting your fermenter in a shallower pan of water (just a couple of inches) and laying a towel over the top with the ends dipped in the water causes water to be sucked up into the towel where it evaporates regularly around the fermenter. This evaporation helps cool the fermenter (just like sweating does for humans). Use of a fan to blow cool air across the wet towel can considerably help this.

A more complex option is to build yourself a fermentation chiller, as per the Son of Fermentation Chiller instructions.

Alternatively, if you have a bit more cash available, you can buy a second hand fridge or chest freezer and attach a digital temperature controller to it to keep your beer bubbling away at your desired temperature.

For keeping beer warm in winter, a similarly large range of options abound, from beer belts (not generally recommended from what I’ve read) to heat mats and even warming wraps!

A temperature controlled freezer can also help to keep your beer warm, providing as it does an insulated box which will naturally warm up during your ale’s exothermic primary fermentation stage, and which should then retain the heat. To make things extra complicated, a heat source such as a light bulb could also be added to the thermostat to provide warmth if the temperature drops – obviously you need to be aware of any potential fire risks if going down this route but it may be worth considering in colder environments.

As I’ll be moving house soon and gaining a lovely new garage for my alcohol-based experimentations, I’m going to wait until I can find a suitable freezer and attempt the necessary electronics. I’ll post the details on here as soon as I have anything useful to share…!


Brew #4 – My First Malt Extract Brew!

So, as you may already know, for Brew #4 I decided to eschew the “just add water” style beer kits that I’ve used so far to give me a taste for brewing, and have a crack at a malt-extract recipe from my handy CAMRA book.

I don’t want to re-produce the recipe in full here as you should really go and buy the book if you’re interested, but for the purposes of this article it’s sufficient to say that I needed:

  • Two cans of pale malt extract
  • some crystal malt
  • four different types of hops (three for bittering and one for aroma)
  • some Irish moss.

As I’ve previously noted, it’s also quite important to remember to buy some yeast … in this instance I’ve used dried English ale yeast.

The basic brew steps were taken from John Palmer’s How To Brew and are described roughly below:

  1. Cleanse and sterilise everything (spoon, thermometer, measuring jug, fermenter etc)
  2. Bring 5 litres of water to a temperature of 70 C (+- 7 C)
  3. Put the crystal malt into a muslin bag and place in water, dipping occasionally like a big tea bag
  4. After 30 minutes, remove crystal malt tea bag (squeezing remaining drops out), pour in another 5 litres of water and stir in one can of pale malt extract
  5. Bring water to a boil, continuing to stir to ensure no malt extract sticks to the bottom of the pot
  6. While waiting for water to boil, rehydrate yeast (pour onto 35 C pre-boiled water in sterilised jug, wait 15 mins, stir gently, wait 15 mins, then pitch within next 30 mins)
  7. Wait for hot break to occur (excess of foam, potential boil overs and proteins bubbling around in liquid – remember at the last minute to add a couple of copper pennies to prevent boilovers) then add bittering hops
  8. Continue to boil and stir occasionally for 45 minutes, then add bittering hops for a further 15 mins
  9. 5 minutes from end of boil, add second can of pale malt extract, stir vigorously to prevent sticking and burning
  10. Fill sink with cold water and ice, transfer pot to sink. Stir wort gently to maximise the amount of liquid touching the cold sides and speed up cooling. Simultaneously run more cold water outside the pot to keep this cool, ensuring that none splashes into the pot. (Wort reached target temperature of approx. 25 C in under 30 mins.)
  11. Transfer entire wort (including hops and, erm, a couple of copper pennies!) to sterilised fermenter. Pour back and forth once more to increase oxygen content in wort.
  12. Violently add 11 further litres of water bringing liquid volume up to 20 litres total.
  13. CHECK OG USING HYDROMETER!!! (Woohoo – I remembered…!)
  14. Pitch yeast.
  15. Please fermenter in warm, dark cupboard and leave for two weeks.

So far so good, although there were a few notes from the brewing process which I’ll jot down here and which may or may not impact the final brew.


I bought a new 3 gallon pot for boiling the wort in which has a raised mound in the center and so only has direct contact with the stove top around the edges.

With a gas oven, this would not be an issue, but we have an electric hob, and the raised mound is almost the size of our largest hob ring, meaning that less direct heat is applied to the bottom of the pot. This in turn means that simple things like boiling water took a lot longer than expected, and the maximum boil temperature was just under 100 C.

This shouldn’t have any impact from a pasteurisation or sterilisation point of view, but it is worth noting. I felt (and admittedly I have no frame of reference) that the hot break was gentler than I was expecting – I certainly was never in danger of a boil over which is marked as a very real danger by John Palmer.

Lesson: To reduce boil times in future, I can either buy a new pot or straddle two hobs to ensure that more direct heat gets through to the wort.

Rehydrating Yeast

Partly because of the extended boil times, partly because of my unfamiliarity with the boil process, the yeast was fully rehydrated over an hour before pitching. I have no idea what impact this would have, although John Palmer does specify that “for best results” the yeast should be pitched within half an hour of rehydrating.

Amount of Yeast

As a secondary yeast related issue, the packet of yeast stated on it that 1g / litre should be used. As this was an 11g packet, and I was preparing 20 litres of beer, I felt I should have had a second packet of yeast.

Unfortunately, the site I bought the yeast from did not specify this and by the time I’d noticed I was halfway through the boil.

Despite this, the packet was still much larger than the usual kit packets of yeast, so I’m hoping for at least similar results to my previous brews.

Lesson: Leave rehydrating dried yeast until the hops go in, or use liquid yeast. I think next time round I’m going to go with option B to increase the amount of yeast strains available, and also to prevent the hassle of having to perform the rehydration process…

Copper Pennies

Although I scrubbed and sterilised a couple of copper pennies before I threw them into the boil pan, they still weren’t what I would call entirely clean looking.

As I poured the cooled wort from the pan into the fermented, I temporarily forgot about the pennies and was more focussed on aerating the wort as I poured it violently back and forth between the two containers.

It wasn’t until I’d pitched the yeast that I spotted one of the three pennies still sat in the boil pot. This means that two are still in with the wort.

Hopefully boiling them for an hour has sufficiently sterilised them that they won’t affect the taste of the beer…

Lesson: Find a way to remove the coppers before cooling the wort (?!) or leave them out of the brewing process entirely.

Watch out for drips…

Another environment specific issue this one, but probably worth mentioning in case anyone else has a similar problem: above our hob we have an extractor fan. Despite this being switched on during the boil, it seems that so much water was evaporated that at one point it was condensing on the extractor fan grill and dripping back into the boiling wort.

Although we keep the extractor fan relatively clean, it’s still been in place for a few years and I would not, for example, eat my dinner off it!

Again, only time will tell whether this has added any unexpected flavours into the brew. I’m reasonably confident that the boiling of the wort will have killed any bacteria (as is the point) but if any grease or dust was washed into the boil pot – well, we’ll see I suppose!

Lesson: Regularly sponge down the extractor fan grill to prevent droplets forming and dripping into the wort.


Don’t Forget Your Yeast!

Not one to waste time in between brews, I decided to order my next brew kit while waiting for my Oktoberfest to condition.

Having performed three kit brews and feeling pretty confident with the basics, I decided that for my next brew I’d try the next step up and use a malt-extract recipe.

Having a copy of CAMRA’s Brew Your Own British Real Ale lying around, I thumbed through to find a particular favourite of mine – Fuller’s London Pride.

The recipe includes all the ingredients needed for full a full grain and an extract brew, so I jumped on t’interweb and duly purchased all the hops, extracts and irish moss needed, plus a few extras.

As I reviewed the ingredients, I had a nagging feeling that something was missing, but despite racking my brain I was unable to put my finger on it…

It wasn’t until a couple of hours after I’d clicked the buy button that it hit me: there was no yeast on the order!

I quickly returned to the CAMRA recipe and realised why I hadn’t ordered any yeast – there was none listed with the recipe … a golden lesson to think for yourself rather than blindly following instructions if ever there was one.

So – yeast. Ok then. Which one…?!

In simple terms we can split yeast from brew shops (as opposed to skimmed from your local microbrewery) into two different states:

  1. Dry
  2. Liquid

From my hurried research on a number of websites and books, I think the following generalisations are true:

Dry Yeast

Comes in fewer varieties due to fact that not many strains will survive the dehydrating process.

Is fairly hardy and can be kept for extended periods of time, but is best kept refrigerated.

Is relatively easy to prepare as it can be simply rehydrated on brew day half an hour or so prior to pitching.

Liquid Yeast

Comes in many more varieties and therefore can be better tailored to a particular beer style.

Historically, liquid yeast has come in smaller packets (50ml) and contained fewer yeast cells than dry packets, and for this reason it was necessary to produce a yeast starter several days before pitching to bring the yeast cell count up to a reasonable level.

These days, some manufacturers provide larger packs (175ml) and ready-to-pitch test tubes which have removed the need for this additional process.

To try and slow the change in my brewing process down – I am already going to have to contend with boiling the malt extract with the hops and cooling it properly before adding to the fermenter, all things I have not done before – I decided to stick with the dry yeast for now as this is a process I am familiar with and should be confident managing.

It will also, hopefully, enable me to see how much the quality of the flavour changes in small gradations rather than big jumps. Seeing how much the boil and hops helps will be fascinating, and then changing to liquid yeast should also produce a noticeable change in quality.

Once I have these processes confidently down (a few more brews at least!) then maybe next summer we’ll start looking at a full-grain mash…!

Brew#2 – St. Peters Ruby Red Ale Beer Kit

So after the crushing disappointment of my first brew, the bar was set fairly low for improvement.

After learning the lesson about fermentation temperatures, I was determined to avoid further potential yeast dormancy issues. So determined, in fact, that I inadvertently chose the middle of a heatwave to attempt my second brew!

However, forewarned is forearmed, and I went into this brew aware of all the potential temperature-based pitfalls. After doing some research on the potential impact to flavour (excessive fruity notes added by high esters generated by over-active yeast) and various homebrewers summer-temperature combating techniques (sit your fermenter in a bath of cool water / surround it with damp towels / blow a fan on it), I decided the best approach was to find a beer which wouldn’t suffer from additional fruity overtones.

Having long been a fan of ruby ales, mainly for their rich fruity taste, this seemed like an ideal time give one a go.

After browsing through various home brew shops online, I finally plumped for the St. Peters Ruby Red Ale kit. I’ve sunk a fair few bottles of their fine concoction in the past, so I had a good idea of how the final brew should taste.

(Although I don’t want to be a “brand slave” it helps when starting out to have a benchmark for what the final product should taste like. This certainly helps me to know whether what I’m doing is successful or not. Taste descriptions written by marketing departments are all very nice, but until you’ve had a successful brew, how do you know whether they ever tasted any good in the first place..?)


I’m still using the basic kit from the Coopers DIY Beer Kit

1 x 16oz Five Star Star San Sanitising Solution

The aforementioned St. Peters Ruby Red Ale Kit

Generic cane sugar bought from local convenience store for priming

Brewing Notes

As before I won’t go into great detail about the entire brewing process as this is fairly generic and can be researched in far more depth and accuracy elsewhere. Here instead are notes on this specific kit / brew that will hopefully help others and me in future…

1. Steriliser

The no-rinse Star San is a dream to use compared to the alternative. Also I used the bath this time instead of the kitchen sink. This has enabled me to sterilise pretty much all bottles at the same time, speeding the bottling process up greatly.

2. Cane Sugar

With the Coopers Kit, priming tablets were included. This time round I used generic table sugar from the shop, adding the correct amount (tables are available in How To Brew) of sugar to boiling water before priming the entire fermenter for even distribution.

The first couple of bottles have not been overly carbonated, which is not a huge problem for this beer, and may be due more to a slight excess of liquid in the original fermentation making the sugar content relatively lower.

3. Mineral Water

This time round I was a lot more careful with the water I used. Living in a block of flats, the water quality coming through our taps is not great, to the point where we see a noticeable difference when using a water filter.

For Brew#1 I used tap water, but this time I used 4 x 5 litre bottles of own-brand mineral water from the supermarket. These were relatively inexpensive (less than a quid each) and also reduce the difficulty in accurately measuring out 20+ litres of liquid.

For additional boiled water, I used filtered tap water in the kettle. At no point did I use straight tap water on this brew.

4. Original Gravity

I totally forgot to take the OG before adding the yeast. This means that I now have no idea what the ABV is. It tastes relatively low strength, but it’s impossibly to know.

One to remember for next time.

5. Rehydrated Yeast

For this brew I rehydrated the yeast before pitching rather than just sprinkling on the dry yeast powder.

It’s impossible to know whether it’s due solely to this, or to the higher temperatures, or any number of others factors (yeast age…? who knows…) or combination thereof, but the fermentation certainly kicked in far quicker and far more dramatically than for Brew#1.*

Either way I think that this is a Good Thing and will probably continue to rehydrate the yeast in future.

* It’s also worth noting that the primary fermentation appeared to finish after only a few days. Despite this the brew was kept in the fermenter for two weeks, but probably could have been bottled sooner. Am too inexperienced to know at this stage…

6. Temperatures

Despite the hot weather, I was able to keep the fermenter in a cupboard in the kitchen (a room which is slightly cooler in our flat due to being on the North-facing side of the property) which kept the temperature fairly steady at around 24 C.

I messed around for a few days with placing freezer packs on top of the fermenter, then got the fear that bacteria-containing condensed water may drip down the side and into the fermenting beer through Coopers’ innovative gas release mechanism and just left it to fend for itself instead. (There was no noticeable change in brew temp while using these so I figured the risk was higher than the benefit.)

24 C is the upper bound of “safe” brewing temperatures for ales, and initial tastings of the beer indicate that brewing at this temperature does not appear to have harmed the flavour in any way, although this could be due to the naturally fruity flavour of this type of ale.

Tasting notes

After 2 weeks primary fermentation and 2 weeks conditioning in the bottle, the results are surprisingly good. (At least they are to me, after the first attempt…!)

As you’d expect from a ruby ale, the deep red colour is very evident, carbonation is light but noticeable, and the beer is slightly muddy after pouring but soon clears.

The taste is full and fruity, possibly more so than usual due to the fermentation temperature, but not unpleasantly so. The beer is light and easily drinkable, possibly a little on the watery side, but I think this may be due to me using a little too much water in the initial fermentation process. (I’ll err on the other side next time and see what happens.)

The overall effect is still that the beer is quite “young” – I intend to leave the remaining 40pts or so for another couple of weeks to see if the additional time helps the flavour develop (as well as for other reasons) – but there would be no problem in drinking the entire batch immediately if that was your aim.

Overall I’m very happy with the way this has turned out and will happily pick up one of these kits again – considering how easy the brewing process has been the results are superb.