Monday, April 16, 2007

Brew #47: Imperial Porter

Too many of my recent brews have been brownish in colour, so it was now time to make something really dark. The intention was to make a normal strength robust porter at around 6.0% abv, but the mash efficiency was pretty good for a dark beer and it came out as an imperial porter. Things could have been worse.

I have had terrible mash efficiencies when making dark beers earlier. Fortunately things went better this time.

An extraordinarily fine crush made by Frode's Crankandstein (or is it Crankenstein monster?) must have contributed somewhat, but not enough to replace the Barley Crusher though. I noticed a lot of dry grain balls in the mash as I doughed in, but a few minutes of stirring made them go way. So it was clear that the crush was much finer than what I have had earlier. There were no hints of any run-off problems, so the crush is fine. I also tried to sparge a little slower than at full speed making it more likely to extract more sugars. Each sparge took about 10 minutes, which is still a reasonably short time. I'll consider reducing the gap my own Barley Crusher for the next brew. It is currently set to the default.

The water in Oslo is extremely soft, very much like the water in Plzen, something that makes it perfect for light beers like pilsener. At the same time this makes it harder to make dark beers. Soft water is really the perfect brew water as it is a lot easier to add minerals than it is to take them out. So to emulate the water of other famous brewing cities one can just add minerals.

I made a porter with 500 grams of chocolate malt and black malt about a year and a half ago, which turned into something very harsh and astringent. I blame the pH of the water. A low pH means a lower mash efficiency and extraction of undesired characteristics like tannins. This time I added 2.5 ts calcium carbonate and 2 ts of 5.2 powder. The recipe also use dehusked dark malts, which should keep the sharp edges out of the beer. I also added the dark malts 45 minutes into the mash, giving the base malt a better chance of converting itself before the pH gets lowered by the dark malts.

The batch was brewed 2007-04-16.

Imperial Porter
All grain, batch sparge
80 EBC (Black)
40 IBU
5000g Pale malt
1000g Munich malt
500g Amber malt
400g Crystal malt, 300 EBC
400g Crystal malt, 130 EBC
250g Carafa I, debittered chocolate malt
250g Carafa II, debittered black malt
68C, 60 min
76C, 10 min (mashout)
72% efficiency
30g Warrior pellets, 13.8%, 60 min
20g Warrior pellets, 13.8%, 10 min
Nottingham, 2 packs, dry yeast, best before date 2007-01-15 and 2007-12-01.
90 min
OG: 1.068 FG: 1.017 (estimated) abv: 6.7%


Travis said...

Congrats on the big effeciency! It sounds like you have that new mash-tun all dialed in now. I have not checked my effeciency on any of my new batches, I make OG and call it good.

How do you figure it out after the fact?

grove said...

I use an application[1] in which I enter all the ingredients and I can adjust the mash efficiency factor to get an OG value. Based on the actual (measured) OG it will tell me the mash efficency.

I'm sure most brewing software will allow you to calculate your mash efficiency. It is quite useful as you can change the amount of ingredients to hit a specific OG.


Ted Danyluk said...

It looks like this will be a nice big beer. The recipe is very close to a Schwartzbier I made recently. The only real difference is in the crystal malts. Also with ale yeast, it may have a nice sweetness. I also used half pils and half munich for the base malts.

I wonder if adding the dark malts later in the mash will effect the overall taste. Have you tried that before? I'm interested to hear how this beer turns out.

grove said...


Yes I do think that the beer will be somewhat sweet, and balanced by a soft roastedness. This is intentional. You're right that it has some similarities with a Schwartzbier hadn't it been for the high gravity, the crystal malts and the ale yeast.

I haven't actually used debittered malts before (husks have been removed). This will supposedly give a smoother roastedness than ordinary dark malts. I added the dark malts late to give the mash a change to properly convert itself before the dark malts where added and lowered the pH. Adding the dark malts late should cause less tannings and astringent flavours to be released. It should also cause a smoother roastedness as well.

In theory. We'll see. :)