Exploration into Decoction Mashing

In the EK Brewers Guild’s quest to be more authentic in our brewing techniques, I have been researching various brewing ingredients, various recipes and now we come to the part about technique.  Decoction mashing, which is a multi step process to obtain the amino acids and starches converted into sugars, is a technique used by German brewers as far back as the 15th century.  Surprisingly, it was very difficult to find period sources that dealt with the history of decoction brewing.  Various websites state that Bavaria and Germany were doing decoction mashing as much as 500 years ago, there was no websites pointing to a source for this claim.

Bolten Brewery established in 1266 produces Alt-Bier (a style of traditional German ale) that can attest to using decoction style mashing.  The term Alt-Bier wasn’t actually coined until 1838, The Dusseldorf Brauerei Schumacher was the first to use the name “alt”.


The decoction mash process being used in large scale with the combination of heated water being added to the grain bill by mash paddle and ladle.

Many sources show that decoction mashes were used in Germany long before the invention of the thermometer which can be traced back to the 15th century.  So why did they do decoction mashing?   2 reasons:

First, temperature adjustments were done based on volume of liquids.  Water always boils at 212*F (100*C).  That is a constant.  If you take 5 gallons of boiling water and pour it into a 10 gallon container along with 5 gallons of water from the well (estimating it’s 50*F)  you are always going to end up with 130*F (50*C) water.  Adjusting the volumes of hot and cold water can help you obtain specific, repeatable temperatures.  By pulling a small quantity of the mash/wort mixture off the original batch and bringing it to boil, you can effectively raise the temperature 10*C at a time allowing for the Saccharification/Enzyme Rest, Protein Rest, and Starch conversion.

Which brings us to the second part of the decoction theory:  We are using what’s called 6-row malt vs the modern 2-row malt.  6-row malt has a higher quantity of protein and enzymes.  These proteins and enzymes can be problematic when creating beers because they add off flavors, clog or create what’s called a “stuck mash” and generally create a beer with less flavor.  Decoction mashing in steps, helps break down these proteins, separate them and convert some to the amino acids needed to make a smoother product.

Original Recipe and Translation:

Johannes Colerum Berlinensem  1596

The German –

X. Capital.
Vom Brewen.
Wiewol ich droben gesagt/dz die weise zu brewen in einem jedern Lande und ort von den Einwonern mus gelernet werden/So wil ich doch hier anzeigen/was wir allhier zu Berlin für eine art zu brewen haben. 1. Schütt man die Gerste in eine Butte/und lefft sie drey Tage und Nacht drinnen weychen/im Winter auch wol viere. 2. Schütt mans auff einen Söller oder Pühne uber einen hauffen/biß es beginnet zu keimen oder zu schiessen. 3. Rüret mans immer ein wenig und aber ein wenig von einander/biß es an den spitzen fein lödicht wird. 4. Wenns genug geschossen oder gewaschen/so bringet mans fein weit von einander/und treugets/entweder in einer Stuben/oder in der Sonnen/oder in einem Dörrofen.

The translation –

Chapter 10.

On Brewing.

As I said above/the wise must learn to brew in any one country and place from the residents/so I want to show here/what kind of brew we have here in Berlin. 1. Put the barley into a butt/and leave it for three days and nights/in Winter four is as well. 2. Put it in a pile or a heap/until it begins to germinate or shoot. 3. One always stirs it a little, but separates a little from another/until it has at the point a made a fine sprout. 4. When it is sufficiently shot or washed/so one brushes the fine parts far from it/and dries it/either in a stove-room/or in the sun/or in a drying-oven.


  1. Mehlet mans auff der Mühlen ein wenig grob/dz sich das Mehl darinnen fein außschelet. 6. Lesset man Wasser in der Pfanne darzu sieden/und schüttet das gemahlene Maltz in die Butten/und geust das heisse Wasser drauff/und rürets umb. 7. Schöpffet mans miteinander aus der Butthen in die Pfanne oder Kessel/und rührets in der Pfanne oder Kessel wol umb/daß das Maltz nicht anbrennet/denn wenns anbrennete/so würde das Bier brandenthend. 8. Legt man Höltzer wie Lattenstück eines neben das ander in die Butthen/und Stroh umbher fein dichte drauff/daß das Maltz nicht durch das Stroh kan lauffen/die Butthe aber mus ein loch/und einen langen Zapffen vorgestackt haben.


  1. Mill the meal a little coarse/so that the meal is finely separated. 6. Let water boil in the pan/ and put the ground malt into the butt/and pour the hot water on it/and stir it. 7. Scoop together from the butt into the pan or kettle/and stir it in the pan or kettle well/that the malt does not burn/because if it is burned/so would the beer be burnt. 8. Put one wooden lath next to another in the butt/and straw around it tightly/that the malt cannot run through the straw/the butt needs a hole/and to have a large tap in front.


  1. Geust man das gekochte Maltz in die Butthen/auff das stroh/und zapffts abe/unn schöpfts oder samlets wider in eine andere Butte darneben/Ist des Maltz es viel/so macht man noch eine Pfanne oder Kessel voll heiß Wasser/unnd geusts auch darauff so viel als man Bier haben wil: Wil man gut Bier haben/so geust man wenig/wil man viel/aber nicht allzu köstlich Bier haben/so geust man viel.
  2. Darnach/wenn das Bier also gesamlet ist von den Maltz/so geust man ein wenig daruon in die Pfanne oder Kessel/das die Pfanne etwan das dritte theil voll bier wird/schütt den Hopffen auch hinein in die Pfanne.
Sol das Bier lange ligen/so nimpt man ein wenig desto mehr Hopffe/sols aber nicht lang ligen/so nimpt man seiner etwan einen Scheffel weniger:und rührt ihn zu erst/und lests darnach miteinander sieden/so lange einen düncket/das es gnug ist/welches durch stetiges kosten mus erfahren werden/unnd da mus man fleissig zusehen/das es ja nicht rohhöpffet bleibet.
  1. Wenn der Hopffe gnug mit dem Biere gesotten hat/so folget man nach mit den andern Bier auff der Böden/unnd geust die Pfanne vollend voll/und lefts damit auffsteden (du darffts als denn nicht mehr umbrüren.)


  1. Pour the cooked malt into the butt/on the straw/and tap it/and draw or collect it again in another butt next to it./If there is a lot of malt/so make a pan or kettle full of hot water/and also pour onto it as much as one wants to have beer. If one wants good beer/then little is poured/if you want a lot/but not too delicious beer to have/so you pour a lot.
  2. Afterwards/when the beer is collected from the malt/then pour a little into the pan or kettle/so the pan is about a third full of beer/put the hops into the pan.

If the beer should lie long/then add a little more hops/but if it should not lie long/one takes a little less from his bushel: and stir it first/and let it boil together/as long as one thinks/that it is enough/which must be experienced by constant tastes/and then you should be diligent/that raw hops do not remain.

  1. When the hops have been boiled enough with the beer/so you follow with the other beer in the cask/and pour the pan full/and leave it to stand with (you must not boil it more.)


So on to the attempted decoction experimentation:

Thankfully I am part of the local Concord Homebrew club and we are able to get 50 lb bags of malt for far less than buying each batch seperately.  I buy most of the bulk malts I’ll need and then buy the smaller quantity of specialty malts required for a batch from the Brew Store.


Original recipe:

  • 10 Lb 6-Row Pale malt
  • 10 Gal Soft Water
  • 2oz Westminster Hops
  • 1oz Westminster Hops


  • 10 Gal Mash Tun
  • 8 Gal Water Pot
  • 6 Gal Wort Pot
  • Metal Spoon / 2 Qty Ladle

We are doing what’s referred to as a Triple Decoction: Protein Rest (40*C), Saccharification / Enzyme Rest(50*C), and Starch conversion (60*C).




Starting off we sanitized our equipment since it hadn’t been used in 4 months.  One of my last batches was questionable whether or not it had been infected during the fermenting process.  The beer had turned very quickly after being in the carboy for a while.

In various group discussions, the use of Soft Water (water with low mineral count) was preferable.  Various beer brewing documents talk about using soft waters for lighter beers like IPA’s, Helles, Whit Beers, Hefeweisen, Pilsners, and Pale ales.  Hard water was better for dark heavy beers like Stouts, Porters, Brown Ales, Barleywines, Bock and Alt Ales.

The night before was the start of the snow storm which gave us a huge quantity of soft water snow.   I melted down an equivalent of snow to make 8 gallons of soft water and it was filtered to remove any residuals.



After grinding the grain, we put it into the mash tun and added our first batch of water to barely cover the grain at 40*C, holding the temp there for 30 min.  Each time we drew off a portion of the batch (roughly 2 qts) , reheated to boiling and introduced it back into the mix.  The first reintroduction was easily accomplished by a simple laudering procedure but the second and third laudering wouldn’t raise the temp high enough so I actually had to get into the mix and stir the mash which I was loathe to do because i was afraid we’d see a stuck mash.  To my surprise, my grain bed sat comfortably on the screen and no grains blocked the wort from running through the bed.



As mentioned, after the protien and enzyme rests, we did the final starch conversion and we saw something not previously seen before.  A grayish rubbery residue clung to the side of the pot we were heating our wort in, as well as a thick coating left on top of the grain bed inside the mash tun.  This worried me because it felt like the 6-row grain had not converted or had done something weird.  I posted the above pics to an advanced home brewing group I’m part of on Facebook and several of the members explained this is a denatured protein sludge that occurs with decoction brewing and that by laudering the wort through the grain bed, I had effectively trapped it in the grain bed instead of it going through to my wort.  These coagulated protiens won’t ferment and I had done the process perfectly by seeing this result.



So after the wort had been drawn off, we ended up with 7 gallons which we immediately started bringing to a boil.  We did a hop session at 60 min at the boil and then another at 15 min to finish boil.  My boil kettle used the period method of cooling the beer, by dropping it in the snow.  After the temp dropped down to 60*F (15*C) we took a reading first with the refractometer showed 12 Brix and the hydrometer showed almost 1.050.  Once the fermentation is done we’ll take another reading and let you know the results.



We are hoping to have the fermentation done in another week and we’ll bring two batches to the East Kingdom Brewers Collegium.  One Oaked and another not Oaked to also show the effects of oak on a beer.  Results will be posted after the event.

Until then…………………………..

4/17/2018  Update:  We entered the Decoction Mash Beer and got an 88 as final score.  This is Grandmaster and although I did well, all the judges had valuable information to help raise my score more. Apparently the paper I submitted failed to talk about the snow use for soft water and they wanted to see a comparison recipe for validation of the grain amounts that were used.  All in all a good beverage.  Wheat beers tend to be a bit sour.  This one had very little sour and it probably needed to be in the barrel another week or so because it didn’t have a high enough vanilla/oak flavor that I would have liked to seen.  More to go…….



  1. Decoction Mashing
  2. History of Decoction Mashing
  3. The Art of Brewing
  4. JOHANN COLER HAUSVATER KOCHBUCH IMMER WÄHRENDER KALENDER REZEPTE WITTENBERG 1593 /Chapter 10 RECIPE:  Brunswick Mumme!  (Special thank you to Michael Suggs  for his sharing of in period source and Google translation.)
  5. Alt Bier
  6. Decoction process
  7. Invention of the Thermometer
  8. Period Decoction Mashing

One thought on “Exploration into Decoction Mashing

  1. Pingback: Most Medieval Beer IV: The Finale | Inn of Bards Rest

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