Experiment – Does Aeration Matter?

Does aeration really matter?

I succeeded in hitting my target of brewing 1000 bottles of beer last year. Now that my challenge is complete, I’m going to concentrate on doing a few homebrewing experiments. Rather than blogging about every brew I do, the plan is to carry out some nicely controlled experiments and write up the results here.

Ever since dramatically improving the efficiency of my mash tun with a new homemade false bottom (I had no idea the geometry of the mash tun would make such a difference – drawing the wort from the centre of the bottom rather than the edge had a huge effect) I’ve been brewing beers with high final gravities, that is, lots of unfermented sugar left in the beer. The improved mash tun efficiency means I’m getting a lot more sugar out the grain, but not much more sugar actually turning into alcohol. I plan to figure out what’s going on over the next few months.

The first idea to test is aeration. Yeast needs oxygen for good fermentation. And boiling removes oxygen from liquids. So, after you’ve cooled down your wort you’re supposed to vigorously stir it, shake it about (or if you have the right kit, inject oxygen into it). I’ve always gone with the stirring technique but have got a bit lazy recently. Maybe this is why I’m ending up with unfermented sugar?…

So, using one of my favourite bitter recipes, my experiment was to brew a batch as usual, then dived the wort into two fermenters, one would be treated gently (bitter A) the other would be vigorously stirred (bitter B).

Bitter A on the left, Bitter B on the right (all frothy from vigorous stirring)

Bitter A on the left, Bitter B on the right (all frothy from vigorous stirring)

I measured the specific gravity (sugariness) regularly during fermentation to track what was happening. After just 24 hours it was clear that the aerated wort was fermenting faster. After 3 days I did something that you’re not supposed to do. I gave Bitter B another good stir. If you add oxygen later in the fermentation process you can oxidize the beer. And that tastes bad. What I didn’t realise is that it also appears to upset the yeast. In the end, the beer without any aeration (Bitter A) achieved a lower final gravity that the one that was over-aerated.

aeration chart

Two lessons here. 1) Aeration does matter. 2) you really shouldn’t aerate after fermentation has started. I’m waiting to taste whether Bitter B with be noticeably oxidised, but even if it doesn’t I now know it’s a bad idea.

And the next thing to test…. How much aeration is needed? I should be aiming for 8 to 10pmm of dissolved oxygen but there is no easy way for me to measure that. I’ll do the same experiment, but this time beer A will be stirred a bit and beer B will be stirred a lot. Do I really need to waste time stirring for several minutes or is “just a bit” ok?

Homebrew: DDS Dunkel

D.D.S Dunkel (dark lager)

Beer style: dunkel (dark lager)
Target ABV: 4.5%
Hops: Fuggles and Saaz
Ready for drinking: from 1 Jan 2015

I want to brew a really complex and interesting ale/lager hybrid. I also wanted to try out a new “no sparge” technique. See here for details. It worked brilliantly. No more sparging for me!

I’ve named after the newest arrival in the lovely Sharrocks family. Daniel’s initials are DDS and therefore so it the beer.

The result is not bad (I mean the beer, not the baby!). Not very lagery but pretty tasty and has a certain freshness and spiciness from the Saab hops presumably.

This is the last general brewing blog I intend to write. Last year I succeeded in hitting my random target of brewing 1000 bottles of beer. Now that my challenge is complete, I’m going to concentrate on doing a few experiments. Rather than blogging about every brew I do, the plan is to carry out some nicely controlled experiments and write up the results here.

Homebrew: Horizon IPA

HorizonHorizon IPA

Beer style: “Red” IPA
Target ABV: 5%
Hops: Fuggles and Bramling Cross
Ready for drinking: from 1 December 2014

Another excuse for a brew. This time the launch of a project at work. The project is called “Horizon”, hence the name. My hope was to brew a classic English IPA, hoppy and rich and complex, not like all the super-citrusy American-style IPAs that are all the rage right now. Worthington White Shield is a personal favourite in this style.

The result was rather darker than I’d hoped. I used 60% pale malt, 7% crystal malt, 25% munich malt and 8% amber malt. I should have gone with about 80% pale and will do next time. To cover up my mistake I called it a “Red IPA”. If all the east London hipsters can brew oxymoronic black IPAs then there is no reason I can’t brew a red one!

The result was pretty tasty but could probably take a few more grams aroma hops next time.

Homebrew: Frida Pale Ale v3

nelson sauvinFrida Pale Ale

Beer style: pale ale
Target ABV: 3.8%
Hops: Nelson Sauvin and Willamette
Ready for drinking: from 22 November 2014

Since completing my target of 1,000 bottles of homebrew this year I’ve become rather remiss at posting about individual brews. However, I have been brewing. This was a quick repeat of the summer ale I brewed for my lovely wife, Erin. This batch (with slightly different hops – Willamette in place of Challenger and Cascade) is for Erin to take to Ireland with her in the new year. She’s doing a 3-month cooking course at the wonderful ballymaloe cookery school and obviously needs a few crates of beer to stop her from missing home too much…

The new mash tun continues to be awesome.


Homebrew: Autumn Red Ale

Autumn Red Ale (aka “CPA”)

Beer style: red ale
Target ABV: 4.7%
Hops: Green Bullet and Willamette
Ready for drinking: from 9 November 2014

An exciting day! One small final change to my mash tun and suddenly I’m extracting 50% more maltose from my malt. I’ve been farting around with mash temperatures and pHs and it turns out the geometry of my mash tun is the thing with the biggest impact. Today I added a small length of hose pipe to the outlet of my mashtun (on the inside) so the wort would be flow out from the centre of the container rather than the edge – and it has a massive impact on the wort. My run off started pouring out at 20 degree (brix) rather than 12 degrees!


Overall (assuming a healthy extract of 305 degree litres per kg for the malt) I’m achieving a 79% efficiency. Way better than the 53%  achieved just two weeks ago. Amazing. Such a simple change.insultaed bouler

So this week I’m doing a variation on the Charlotte’s Park Ale brewed a few weeks ago. Different hops, slightly different malts but a similar aim – a nice slightly smokey red ale. The smokeyness was a bit subtle last time so I’ve increased the level of rauchmalt. I’m also trying out some willamette hops for the first time.

I’ve also got a new set of bright red insulation sheets (usually used for insultating a hot water tank) but my idea was to insultate my boiler (aka. a tea urn) to try and increase the intensity of my boil. You’re supposed to have a really strong rolling boil but mine has always been a bit pathetic. Sadly it wasn’t as successful as I’d hoped. My boil was undoubtedly a lot more efficicent but no more vigorous. I will probably need to fiddle with the electronic thermostat in the boiler or something scary like that. An alternative would be to buy a paella gas burner and big pot… The brewshed is pretty full already. Do I really need a whole load more brewing kit?

Homebrew: Prower Pale

Prower Pale Ale

Beer style: pale ale
Target ABV: 4.0%
Hops: Green Bullet and Amarillo
Ready for drinking: from 12 October 2014 (kegged)

This citrusy pale ale is a chance to raise a bit of money for my recently adopted homebrew charity. No – it’s not a charity supporting homebrewers who have fallen on hard times, but a charity that I’m hoping to support with my homebrewing activities. Some times kind people (like Jim Prower, who has requested this beer for his daughters wedding) refuse to take my beer for free, so now I have a charity site to direct them towards. And any donations they make will be very much appreciated by me and by the Kaleidoscope Trust, my charity of choice.

This pale ale is also an opportunity to learn a bit more about the efficiency of my mash tun. I’m hoping for significant improvements since I made the plastic false bottom out of a garden chair last weekend. It was the first time I really bothered to take regular readings with my refractometer during the sparging process. I took readings of the specific gravity (sugariness) of the wort I was collecting and also of the wort running out of the mash tun, every 4 minutes. This allowed me to calculate the volume of sugar I was collecting (assuming a specific gravity measurement of 1.0% brix is equivilent 1g of sugar per 100ml of water which I’m told is true but find hard to believe). It also allowed me to calculate my mash efficiency. Based on a conservative extraction rate of 250 degree litres per kg for the malt I’m only achieving an effiicency of 65% – I would like to be much closer to 75%. If you assume an extraction rate of 305 degree litres per kg for the malt then I’m only achieving 53% efficiency. That’s really low!


You would expect the run off to start really sugary (say 20% brix) then drop down to 3% or so towards the end of the mash. You’re not supposed to continue the sparge lower than that to avoid tannins being washed through and into the beer. My wort is starting at a mediocre 14% and then only dropping to 6% or so – certainly in no danger of any nasty tannins. But that tells me there is lots of sugars left in the grain. Also the fact that my run off shot up to 16% right at the end when I was tipping up my mash tun to get all the good stuff stuck underneath the false bottom in my mash tun (look at the blue line) tells me that the geometry of my mash tun is really not working as effiiciently as it could do. As a minimum I should make sure that I’m collecting the wort from the centre of the false bottom, rather than one end. I should be able to do this by adding some tubing from the outlet into the centre of the bottom of the mash tun. I also may have a more significant problem with the space under the false bottom being too big. There isn’t much I can do about that as the tap won’t go any lower.

Before I resort to buying an expensive but very tempting mash tun like this one, I’ll make a few more changes to my mash set up and see how much I can improve.

Homebrew: False Bottom Porter

‘False Bottom’ Porter

chair and mash tunBeer style: porter
Target ABV: 4.0%
Hops: Green Bullet and Goldings
Ready for drinking: from 22 October 2014 (bottled)

I’ve come to the end of my year of homebrewing – brewing 1000 bottles was the challenge I set myself; it took me a few extra weeks but with this brew I hit the 1000 bottle mark. To celebrate I made a false bottom for my mash tun!

Over the next year I’ll continue to play with new recipes, develop the existing ones and hopefully improve my homebrewing techniques. The efficiency of my mash (how much sugar I manage to extract from the malted barley) has always been low and over the next few brews I’ll try to work out why and if possible improve it. First step – to improve my mash tun….

Previously I’ve used a mash-bag to contain my grist (the malted barley). It’s like a massive teabag. This sits in my mash tun and stops all the malt clogging up the tap in the bottom of the mash tun. Unfortunately the bag means that there is a easy path for the water around the outside of the bag rather than through the grist. And getting the water to flow through the grist when you’re sparging, to wash out the sugary goodness, is the main aim.

false bottomSo, the alternative is to create a false bottom to the mashtun and get rid of the bag. The false bottom is just a sheet of plastic with loads of holes in it. It sits in the mash tun an inch or two above the bottom, above the tap but below all the grist. I made my false bottom out of the seat of an old garden chair. A few hours of cutting out the sheet of plastic into the right shape, and a few hundred 3mm holes later, my new mashing equipment was ready.

It’s been a while since I brewed a porter or stout. It just doesn’t happen so much during the summer. This is a variation on an old milk stout recipe I brewed last year. It’s got no lactose in it (the milky bit of a milt stout) but has lots of roasted barley, chocolate barley and a good few handfuls of flaked oats. I’m trying out a new variety of hops, a bittering hops called Green Bullet from New Zealand. The new mash tun set up worked well. During the next brew I’ll remember to record the sugar levels periodically through the sparging so I can really get a feel for how to optimise extration levels. I want to avoid water escaping round the edges of the false bottom but should be able to spot it happening if I’m getting track of the extraction rates.

Homebrew: Charlotte’s Park Ale

Charlotte’s Park Ale (a slightly smoked red ale)


Beer style: red ale
Target ABV: 4.7%
Hops: Challenger and Goldings
Ready for drinking: from 10 Sep 2014 (keg)

Rauchmalt is a german smoked malt. It’s used in large quantities for rauchbier, which is often incredibly smokey (and sometime delicious with smoked salmon or smoked meats). It’s pale like pale malt – but smells of barbeque. In this red ale I used about 7% rauchmalt. I wanted a fairly lightly hopped ale with a hint of smokiness and a good red colour. Considering we drank this keg in Regent’s Park out of green and blue plastic cups I can’t really confirm the success of the appearance – but it tasted ok. Could have done with a few more late hops thrown in – and perhaps a less bumpy journey to the park.

Interestingly, all malt used to be smoked due to the lack of control in the malting process. Like pale malt (and hence pale ales and pilsners) unsmoked beer is a pretty recent invention.

Making my first ever “red ale” made me question wher0e the sytle comes from. You get flemish red ales (like the famous and marveollously complex duchesse de bourgogne beer – think ale with a hint of sour compost) which this definitely was not. And you get Irish red ales. There wasn’t much that was Irish about this beer (hop varieties were both british) but this was the style I was going for. It seems to me that Irish red ale is just an Irish name for an lightly hopped English bitter. I think lots of microbreweries are brewing “red ales” to appeal to the east london hipster who will happier order a “pale ale” but would hesitate to order a “bitter” .

Hopefully with a bit more smokiness and a few more aroma hops this’ll develop into a nice little recipe.

Homebrew: Brewshed ESB

radioBrewshed ESB

Beer style: ESB
Target ABV: 8%
Hops: Challenger and Goldings
Ready for drinking: from 10 Sep 2014 (bottled)

So many pale ales recently. I thought something a bit more serious would be good and am aiming for my highest ABV yet at 8%. To up the alcohol content I added a bit of treacle to the boil. Extra sugar = extra alcohol. Hopefully boiling up the treacle with the wort for 90 minutes will add a nice burnt toffee flavour. It’s going to be deep and red and full of British hops. I hope it’ll be a great post-dinner drink to share – something nice to go with cheese.

And a perfect day of brewing in the brewshed and listening to England win the cricket.

Homebrew: “Double Bill” Pale Ale

“Double Bill” Pale Alerain

Beer style: Pale ale
Target ABV: 4.5%
Hops: Challenger and Amarillo
Ready for drinking: from 2 Sep 2014 (bottled)

Another variation on a pale ale recipe. This one has a a good bit of wheat in it for good body and head retention – not too hoppy. It’s for yet another wedding. This time for the lovely Tom and Hannah at the Cinema Museum in Kennington – hence the random name.

It was actually a real pleasure to get back to the joy of bottling after so much summer kegging. It’s very satisfying to get all the bottles cleaned up, capped and boxed up – even if it does take hours.

The brewshed is continuing to make the whole process a whole lot quicker – though I haven’t quite figured out bad weather brewing yet…