Tag Archives: double decoction

My Summer Beer 2022

Like last year, I decided for 2022 to brew a light and refreshing beer for the the summer. I was really really happy with my 2021 beer, and so for this year, I again brewed an 8° Czech-style beer, this time even more traditional than last year.

And that was my exact approach: be as simple as possible, but stick to the ingredients that would constitute a Czech beer according to PGI (if I brewed commercially in the Czech Republic and wanted to sell my beer with a Czech Beer PGI label): the sugar from the wort needs to be at least 80% from Czech barley varieties, at least 30% of the alpha acid needs to come from Czech hops varieties, decoction mashing needs to be used, and the beer needs to be bottom-fermented. So I went all in:

The brewing and fermentation process itself was rather uneventful: I hit 8.4°P OG, chilled the wort to 10°C, pitched a yeast pack, fermentation took off in less than 36 hours, and after about 3 weeks, it was finished, with a FG of 2°P. I then ramped down the temperature to 2°C, let it sit at that low temperature for just 2 weeks, and then bottled it, bottle-conditioning it with 1 liter of wort that I kept back.

I’m absolutely impatient when it comes to waiting for beer to be finished maturing and bottle-conditioning, so I had to crack one bottle open after just 1 week. I pre-chilled it for a few hours, and then poured it into a Pilsner Urquell glass I had at home. While carbonation wasn’t 100% there yet, it was definitely enough to drink it. The foam was fluffy but with rather big and open bubbles (I hopes this improves when carbonation is higher), the beer still looked slightly hazy with a very pale colour). It smelled absolutely amazing, and just after the first sip I could definitely say that this was exactly like a Czech beer (it’s not a Czech beer because I brewed it here in Berlin, hence why I call it Czech-style). It has that exact bitterness and the kind of hop flavour and aroma that I would expect from any Czech beer, it has a unique edge to its malt character that I would attribute to the intense decoction mash (hard to describe, but once you’ve had plenty of Czech beers, you just notice it, from your easy-drinking 10° beers to modern Czech-brewed IPAs e.g. from Matuška), and it’s got a very good body for such a low-strength beer.

The Urkel Lager strain, despite (allegedly) having a Pilsner Urquell provenance, does not seem to produce diacetyl at any detectable levels. What it does though is produce lots and lots of sulphur. This was particularly noticeable during fermentation and at the beginning of the very short lagering period, but at packaging, all of that was gone.

In the end, choosing the right ingredients and processes for the kind of beer you want to brew matters, and I’ve only ever gotten all the details of a Czech-style beer right when I applied all the techniques that I knew, with all the right ingredients.

What follows is a quick recipe. In terms of ingredients, it’s incredibly simple and one of those beers that can be formulated as a SMaSH beer – single malt and single hops. In this case:

  • 3.1 kg floor-malted Bohemian Pilsner malt from Weyermann
  • 24 g 2021 harvest Saaz hops (4.2% ABV) @ 60 min
  • 24 g 2021 harvest Saaz hops (4.2% ABV) @ 30 min
  • 24 g 2021 harvest Saaz hops (4.2% ABV) @ 5 min
  • 1 pack Imperial Yeast L28 Urkel Lager yeast

Use enhanced double decoction mashing scheme. Lauter, sparge, chill to 10°C, pitch yeast. Ferment fully, lager at low temperature for 1 week (I went down to 2°C), bottle or keg and carbonate. This should get you about 20 liters of a beer with 8.4°P OG, 2°P FG, 3.4% ABV, about 25 IBU in bitterness, and a very pale colour.

Interpreting a 1960s Bavarian Dunkel Recipe

Whenever somebody asks me how I would brew a Bavarian Dunkel, I have to respond that I never actually brewed one on my own. Instead, I rather point to an authentic modern-ish recipe from a Bavarian brewery from the 1960s.

A few years ago, Urban Chestnut Brewery from St. Louis, MO posted a sheet from 1967 brewing records of Brauerei Erharting in Bavaria. Their brewmaster, Florian Kuplent, had originally apprenticed there, and most likely got his hands on these records that way.

The recipe is interesting because there are a lot of assumptions baked into it that you’d only know if you had an idea about Bavarian brewing. It also challenges conventional wisdom that Bavarian brewers would just brew their Dunkel from 100% Munich malt. At least in the 1960s, this was not true anymore for this recipe.

This recipe for Export Dunkel starts with the grist: it simply says 1350 kg of malt, of that 50 kg pale malt (lit. “Hellmalz”), 50 kg CaraMunich (originally CaraMünch, the German brand name), 10 kg roasted malt (Farbmalz in the original). What the recipe doesn’t say is the rest. The use of Munich malt (likely on the darker side) was simply implied from the type of beer that was being brewed. The pale malt was most likely a Pilsner malt. That way, we end up with a grist like that:

  • 1240 kg Munich malt (91.9%)
  • 50 kg Pilsner malt (3.7%)
  • 50 kg CaraMunich malt (3.7%)
  • 10 kg roasted malt, e.g. Carafa special II (0.7%)

Why the Pilsner malt? I can only speculate, but I assume that this might have been formulated under the assumption that the Munich malt had so little diastatic power that it would only self-convert and not fully convert the (enzymatically inactive) caramel and roasted malts.

The next part is the mash. It starts with doughing in the malt and letting it sit for 20 minutes at 35°C. This was typically done to ensure that all the malt was fully hydrated. Nowadays, this would be ensured through a pre-masher that would combine water and malt just before it goes into the mash tun.

Then, the mash was heated up to 52°C within 15 minutes. The mash tun must have been heatable.

The recipe then further mentions to mashes. For the first mash, 22.5 hl of mash were pumped into the kettle while the stirrer was running. In the kettle, the mash the underwent a multi-step mash on its own: 10 minutes protein rest at 52°C while a bit of wort was drawn off (Malzauszug) and kept in the Grant, 10 minutes saccharification at 60°C, 10 minutes saccharification at 65°C, 70°C until iodine test was negative and the mash was fully converted (normally 20 to 25 minutes) and then 75°C for another 5 minutes.

This step mash prior to boiling the mash is done to maximize the use of the enzymes that will eventually be destroyed, and to convert as much starch as possible, so that the intense boil will only extract some more starches to be converted in the second mash.

Then the mash was brought to a boil, boiled for 35 minutes and then mixed back into the main mash which then reached a temperature of 65°C.

Then the second mash started: 23 to 23.5 hl of mash were again pumped into the kettle, rested for 10 minutes at 65°C, then again rested at 70°C until iodine test was negative, and then 10 minutes more at 75°C. It was then boiled for 25 minutes, and mixed back into the main mash to reach a temperature of 74°C.

The wort that was drawn off must have then been mixed back in, the recipe is not fully clear on this, though. I don’t know exactly why, but I assume that this was done to retain some amylase enzymes and ensure that some end up in the mash just before lautering to help convert any last few bits of starch (even though this is unlikely given how thorough the extraction must have been through 2 long decoction boils).

Then lauter and sparging happened to collect about 100 hl of sweet wort which was then boiled for 2.5 hours. The resulting amount of wort at the end would have been 78 to 79 hl with an OG of 12.7 to 12.8 °P.

The hopping schedule looked like this:

  • beginning of the boil: 4 kg Hallertauer hops
  • 1 hour after beginning of the boil: 4 kg Hallertauer hops
  • 45 minutes before the wort is pumped off the kettle: 3 kg Spalter hops

The last one is particularly important: the timing does not depend on the end of the boil, but rather on when the wort is moved from the kettle to the chillers. None of the hop additions come with any indication of alpha acid content. There is one source though where we can get an estimation: international hop trader Barth Haas has its full range of historic hop reports online, both in German and English. The 1966-1967 report in English at least reports the “bitter value Wöllner” for some hops: 6.2 for Hallertauer hops and 6.6 for Spalter hops, both from the 1966 crop.

This “bitter value Wöllmer” was an early approach to estimate the bittering quality of hops. In particular, this value is calculate as alpha acid % + beta acid % / 9. For both Hallertauer and Spalter hops, we can assume that the alpha acid content is roughly the same as the beta acid content.

6.1 = x + x / 9 and solving for x gets us an alpha acid content of about 5.5% for Hallertauer hops.

6.6 = x + x / 9 and solving for x gets us an alpha acid content of about 5.9% for Spalter hops.

Bear in mind that these are just estimations, but should nevertheless give us a general idea about whether these were more high or low alpha acid for the variety.

And this is how you interpret a 1960s German recipe for Bavarian Dunkel.

Double-Decoction Mashing on a Home-Brew System Not Designed For Decoction: A Post-Mortem

Today, I brewed together with Ben Palmer at the MASH PIT, a kind of nanobrewery/home-brewing co-working space that allows you to brew your own beer on the brew kits installed there. Ben had recently moved to Berlin, and since we knew each other through Twitter, we met up and eventually decided to brew a beer together.

One thing that I’ve been wanting to do for a long time at the MASH PIT was to brew a beer using a decoction mash. Ben was also happy to do that, so we agreed on a simple recipe. Our grist consisted of 98% Pilsner malt and 2% CaraMunich II, while the hops we chose were Celeia (Ben had never used Slovenian hops, and since I hadn’t either, I was happy to also try them out). The original idea was to ferment it with a Kölsch yeast, but since we were informed that the MASH PIT had run out of that yeast the day before the brew day, so we substituted it with Nottingham Ale yeast instead, another fairly neutral and attenuative top-fermenting yeast. For mashing, we wanted to do a double decoction, for several reasons: my reasons were that I wanted to try brewing a double-decocted beer on the MASH PIT kit, and I also wanted to try brewing an ale of some sorts that had a distinct decoction character. This was something I had stuck in my head ever since my last visit to Prague, where I tried a few ales [sic!] from Pivovar Matuška, and they all had a distinct “Czech” flavour that I could only attribute to decoction mashing. Ben’s reason to try out double decoction was that he hadn’t really much experience beyond a few demonstrations at his vocational school.

A few words on the MASH PIT brew kit: it is fairly simple and straight-forward. It consists of three large pots of maybe 75 litres volume (the scale only goes to 65), all equipped with taps on the bottom and the top and embedded thermometers. One of these pots is sat on a gas burner and mainly serves as kettle to boil the wort as well as to heat up the liquor (brewing water). The middle pot serves as mash and lauter tun and is equipped with a removable false bottom. It also comes with a RIMS attachment that allows you to pump wort (a liquid pump is part of the setup) from the false bottom through the attachment and sprinkle it again on top of the mash. The attachment has a heating element that can be turned off and on. With this setup, you can do a multi-step infusion mash fairly easily. The third pot is also equipped with an electric heating element and mainly serves as hot liquor tank (HLT). Through three switches, you can turn on and off pump, RIMS heating element and HLT heating element.

But instead of following this scheme, we instead decided to repurpose the kit for decoction mashing. With about 11 kg of grist, we filled the mash tun with 44 l of liquor at 45°C, then mashed in. This increased the overall mash volume to 55 l. The mash temperature was 41°C. After a short rest, we pulled 36 l (i.e. two thirds) of thick decoction and moved it over to the kettle. We brought the decoction up to a temperature of 70°C, which went very quickly thanks to the powerful burner. A quick rest of 15 minutes to at least partially convert the available starch, and then brought the mash up to a boil. That’s where the problems started: we had a bit of a boil-over, which was our mistake as we partially covered the pot with the lid and also kept it unwatched. After a quick cleanup and making sure we hadn’t lost much of our decoction, we continued boiling it for another 10 minutes.

A watched pot never boils, an unwatched pot boils over.

We then started mixing the decoction back into the main mash. We noticed that even though we had moved only about 50% of the decoction, we were already overshooting our target temperature of 65°C. That was not good. We had to improvise somehow, and so we decided to add some more cold water to the decoction to bring its temperature down. We eventually got that done and ended up with a mash at pretty much exactly 65°C, but now with a total volume of more than 60 litres, which we left to rest for 50 minutes.

So obviously we had overdone it with the decoction volume. I had chosen two thirds as the initial volume because that’s what had worked for me at home on my home-brew kit. Except my kit at home is for 20 litre batches, while this system is for 50 litre batches. I realize that my home system is at such a small scale that boiled mash can cool down fairly quickly, but I didn’t think that effect would effectively disappear at at scale-up from 20 to 50 litres.

The change in mash volume also meant that any previous estimations of the volume for the second decoction were out the window. We then decided to just estimate it to one third of the total volume, and then a bit, so the second decoction we pulled was thin and sized at 25 litres.

We brought this second decoction again to a boil, boiled it for 5 minutes, and then mixed it back again. By that time, the main mash had cooled down to 61°C, so the final temperature after mixing back was only 71°C. Not exactly the 75°C where we wanted to get to, but still good enough. We then left the mash to rest for another 30 minutes and prepared for lautering and sparging: we cleaned the kettle, filled up the HLT and heated the sparging liquor.

With everything prepared, we decided to just skip the iodine rest (YOLO, right?) and started a vorlauf. We only got very few hard bits and very quickly got a very clear wort. We then connected the mash/lauter tun’s tap to the kettle, and slightly opened the tap. Lautering went quickly and ran off smoothly, looking very clear and bright. We then started sparging by pumping liquor from the HLT onto the mash, breaking up the stream with a highly technical piece of equipment: the mash paddle.

Kettle in the front, sparging action in the back

We managed to collect a total of 63 litres of sweet wort. In the end, this was limited by gravity: at 63 litres, the level of the wort was the same as the tap of the mash/lauter tun. We then starting bringing the wort to a boil.

Ben then had the idea that we should check the gravity of the last runnings with the refacrometer that we had used to check on gravities during the process. Turned out, the “last” runnings still were at more than 5°Brix. Instead of just conceding to the laws of gravity, we should have lautered the last remains into a separate vessel and topped off the kettle instead. It probably would have also helped with another issue we noticed: according to the refractometer, the pre-boil gravity was at 12.4°Brix. Our plan was to have an OG of 11.8°P (°P and °Brix are very similar scales, and virtually identical and practically interchangeable). So strangely, we seemed to have a much higher OG to expect than what we had planned and calculated. Of course, we didn’t know what extract efficiency to expect on this home-brew kit, but still.

We decided to continue with boiling the wort anyway, and added hop additions at 90 minutes and 5 minutes before flame-out, and then more during whirlpool. Post-boil gravity according to the refractometer was at 15°Brix. This was way too much, and would have meant a much greater efficiency than what we could have planned for.

We then sent the hot wort through the plate chiller to the fermenter at a nice 18°C, and measured the OG using a saccharometer. It really was at 14.1°P. This was weird, a difference of almost one degree. I then rechecked the refractometer with just water, and it turned out that refractometer wasn’t properly calibrated.

Another problem also popped up when pumping the wort from the kettle through the plate chiller to the fermenter: towards the end, we started pulling in hot break and hop particles. We were then told that they actually had a hop filter that we should have attached that would have allowed us to get more of the wort from the kettle to the fermenter without sucking up any of the gunk. We had to stop the pump early, and only ended up with about 45 litres of wort, but at a higher OG than we what we wanted.

Our solution to that was simple but almost embarrassing: we decided to dilute the wort with cold water to bring the OG down to 12°P. The final step was then to hydrate the yeast (3 sachets of Nottingham Ale yeast should do just fine) with some fresh wort, pitch it, and move the fermenter to the temperature-controlled fermentation room.

The day was concluded with lots of cleaning up and a glass of cold, fresh beer from the MASH PIT tap room. A lot of things went wrong during the brew day, but we managed to salvage any issues, and still arrived at something that I think should come out pretty nicely. I’m definitely looking forward to trying out the resulting beer. The main things I want to see is whether I really do get a pronounced decoction character in the beer, and of course, what Celeia hops taste like in a beer.

A brewing selfie. We were smiling under these masks, I swear.

Mahrs aU Clone, Iteration 1

As I’ve announced a month ago, my homebrewing project for 2020 is to develop a clone recipe for Mahrs aU. I brewed the first iteration on December 27, and here’s a quick report on how that went:

My grist was fairly simple, 2.4 kg Pilsner malt and 2.4 kg Munich I malt, both from Weyermann. I doughed in with 20 litres of water which I had treated with 6 ml of lactic acid (something something counteract local water’s hardness, I calculated this ages ago and stuck to it since, I’m terrible with water chemistry). I then conducted my preferred double decoction mash where I start with a very large thick decoction, rest it at around 70°C when heating up, then boil it and mix it back, and then pull a thin decoction, boil it, and mix it back again. The temperature steps the main mash was undergoing in this case were 39°C (dough-in temperature), 62°C and 72°C. I then moved the mash to the lauter tun, recirculated to get clear wort and then started lautering, measuring 17.6 Brix on the first runnings. I continuously sparge, and after 30 minutes, I had enough wort collected to bring it to a boil. Pre-boil gravity as determined by refractometer was 11 Brix.

After 90 minute boil, with hop additions (2019 harvest Perle, 7.2% alpha acid) at 90 minutes (32g) and 10 minutes (10g) before the end of the boil, I moved the wort the a fermenter and chilled it down to 10°C before adding two rehydrated sachets of W-34/70 yeast. Fermentation took off about 36 hours after pitching the yeast.

Things didn’t go quite as planned, as the wort’s OG turned out to be 13.3°P. My grist calculation was based on previous batches in which I employed the same mashing regime, but this time, for whatever reason, efficiency was quite a bit better than what I wanted to achieve. I’m not going to complain about it, as it’s only 0.6°P (roughly 0.002 in gravity points) higher than where I wanted to get to.

Fermentation was quite a bit slower than usual. I’m not sure why, but I may have rehydrated the dry yeast improperly, therefore slightly underpitching. Even after four weeks, fermentation did not seem quite finished. I would have waited, but two days ago, another problem came up: the seal on the fermenter’s tap was leaking. Not a whole lot, but in the tray underneath, a few hundred ml of beer had built up. Since this was just the first iteration, and things weren’t 100% right from the beginning, I decided for an emergency plan: instead of lagering properly, I just cold-crashed the beer, hoping not more would leak between Friday and today, and then bottled the beer today. With 4.4°P, I’m not 100% sure the beer had completely finished fermenting (though there wasn’t really much of a noticeable residual sweetness), but I bottled it anyway and just let it naturally carbonate over the next few weeks. To be frank, I’m not particularly happy with that, but given that things weren’t right from the beginning, it’s still an acceptable shortcut for a first iteration.

A quick taste test directly from the fermenter revealed that the beer indeed tasted remarkably close to the original Mahrs aU. While the beer was pretty clean-tasting, the hop bitterness still seemed a bit rough. My concern is that whenever this has aged a bit and smoothed out, the bitterness might not be quite high enough. Bear in mind that I based the hop additions and overall bitterness just on some very flimsy circumstantial evidence. Since then, I’ve received multiple pointers to other sources talking about the Mahrs aU parameters, such as this very helpful comment by DB who mentioned that Michael Jackson had written about aU in 1999, when it was still bittered with Northern Brewer and Hallertauer Tradition to 36 IBU, and this reply on Twitter pointing out that Ron Pattinson’s book Decoction! (seriously, you should buy it) contains OG, ABV, real extract, apparent attenuation, colour and bitterness from the year 2000 for “Mahr’s Bräu ungespundet – hefetrüb” (aka Mahrs aU), setting the bitterness at a whopping 42.5 EBU.

I’m still waiting for the bottled beer to condition and slightly mature before I’ll start a proper taste test the results of which will then be the basis for my next step. Based on the brew day itself, I will probably slightly reduce the amount of malt the next time so that I can get closer to 12.7°P in OG than the 13.3°P of the first iteration. Also depending on how the bitterness shines through, I may slightly increase the bittering hops.

I also chucked out that particular fermenter and ordered myself a 30 litre Speidel fermenter instead.

Why a Triple Decoction Mash Can Never Fail

I’m currently working on a new project, so as part of that, I’ve been reading quite a few historic descriptions of decoction mashing, in particular triple decoction which historic literature generally describes as the standard mash schedule in Bavaria, Bohemia and Austria around the 1870’s-1880’s.

When I played a bit with calculating the right mash volumes and the mash temperatures, I stumbled upon an interesting property of standard triple decoction: you can’t get it wrong. You actually have to actively try and sabotage it for it to fail.

This is a really cool thing because triple decoction sounds so ancient and complicated and easy to do wrong, and I think that scares a lot of people who then shy away from trying it out, but if you follow a few simple principles, you can’t go wrong at all.

These principles are:

  • always pull 1/3 of your total mash volume as decoction
  • pull the first and second decoction thick (i.e. mostly malt with little liquid), and the third decoction thin (i.e. mostly liquid)
  • bring each decoction to a boil, boil for a bit, then mix back into main mash
  • make sure you measure your volumes exactly, work quickly when mixing back, but also mix thoroughly
  • when doughing in, give the enzymes some time to get dissolved before starting to pull your first decoction

From a historic point of view, triple decoction was a reliable method to guide your mash through a number of particular ranges of rest temperatures to facilitate the activity of specific enzymes to convert long proteins into shorter protein chains and to convert starch into simple sugar molecules and shorter dextrin chains to both achieve a fermentable wort and a good mouthfeel, without requiring a thermometer.

And when you apply some maths, and draw a pretty graph, it really shows that all you need is the ability to vaguely judge your initial mash temperature to be between somewhere slightly above room temperature and slightly below tepid, and everything falls right into place, provided you follow the principles above.

The general equation to calculate your decoction volume is:

decoction volume = total mash volume * (target temperature – start temperature ) / ( boil temperature – start temperature)

If we assume the total mash volume to be 1, and our decoction volume to be 1/3, we can rewrite this to

target temperature = start temperature + 1/3 * (boil temperature – start temperature )

Based on this, we can easily calculate whole temperature series if all we do is repeatedly pull decoctions that are 1/3 of the whole mash volume, bring them to a boil, and mix them back.

I’ve done this in a spreadsheet, and put this into a nice temperature/time chart to indicate the time schedule your mash steps would follow. In total, I’ve done this with four different initial temperatures: 20, 25, 30 and 35 °C. This is a rather wide temperature range, but it’s also one where most people could easily and correctly judge whether a liquid is within that temperature range just by feeling with their finger or elbow. To keep the chart readable, I’ve only added the main mash temperature, and left out the temperature curves of the decoctions. To account for cooling during mixing back, especially so on a homebrew scale, I assumed a boiling temperature of 95 °C instead of 100 °C.

Triple Decoction Mash Temperatures

In addition, I’ve marked the temperature ranges in which you reasonably want to keep your mash to do a protein rest, as well as to give the alpha and beta amylases good conditions to do their work.

When you now look at the chart, it is very noticeable that at all stages (protein rest, maltose rest, saccharification rest/mash-out), all our target temperatures fall within the desired temperature ranges. The further we go, the more all the temperature curves converge towards a narrower and narrower temperature range, even though we started with a very wide one. This makes it very hard to screw up, even if you e.g. slightly miss your target temperature after your first decoction: you will still be well within the desired temperature range.

In addition to that, when you bring up your decoctions, in particular the first one, to a boil, they go through these temperature ranges as well. Some modern mash schedules recommend doing at least a saccharification rest to optimally use the enzymes that will later get destroyed, so you can have an infusion step mash within your decoction. Even if you don’t do it, unless you heat up very quickly, your decoction will at least partially convert when you heat it up.

And this is why your triple decoction mash can never fail: when bringing your decoctions to a boil, they will partially, if not mostly, convert, and then release more starch during the boil, which will then be fully converted in the main mash. There are two decoctions where the enzymes get into the right temperature range to convert starch into sugar, and there are two rest steps where the enzymes have even more time to convert more starch into sugar. Your whole mash goes through the right temperature so many times, it will eventually be fully converted. And to get into these right temperature ranges, all you need to do is follow a few simple principles. And if you want, you could even do this totally without a thermometer.

For most modern malts, triple decoction is possibly a bit to harsh, in particular when it comes to the extended protein rest which could potentially be very damaging to foam stability. For this, you can also employ an enhanced double decoction, in which you start at the same temperature as a triple decoction, but pull double the volume for the first decoction, and do a step mash of your first decoction before boiling it. That way you keep the intense treatment of your malt, but can keep the time within the protein rest range to an absolute minimum.