Double Brew Day - Double lesson learned day. On strike temperatures for mashing

This was meant to be a blog post on the double brewday that I did yesterday. I finally got round to re-brewing the Nelson Sauvin stout that I brewed in January for AG0010, and then whilst I was brewing that, I tasted a bottle of AG0020, the First Love, Fruit Salad IPA. It was bitter as all hell as I’d not scaled the amount of hops with the lower grist bill.

It was meant to be a discussion on all of that, but it’s not going to be. That may be later, today, this blog post is about a very important lesson I learned yesterday. Mash Strike Temperatures.

I live in Manchester, and for the most, it’s not so warm that the temperature plays much of a roll in the mash (it’s hell on the fermentation when it’s cold here). I've been brewing since September and for the most, it’s been pretty cold. So I've gotten used to certain “rules” about certain parts of the brew.

I read most of the How To Brew website by John Palmer, the bit pertaining to this is (this page) where it says “generally the initial "strike water" temperature is 10-15°F above the target mash temperature”. I also got similar information at a Homebrew meet once where a few people were talking about the mash. It was said that as a rule, to mash in about 10°C above your desired mashing temperature.

This “rule” has worked well for me the last 20 brews for the last 9 months, to the point that I even have it as a set text on my brewsheet. I just start the brew off, heat the water up to 10°C above my desired mash temperature, and away I go.

I was tired as all hell yesterday due to problems at work the night before (not so important, mainly that I was tired) but I got up after 4.5 hours sleep to start the water heating up for my mash, and away I went.

I was using 6.525 kg of various malts with a mash in of 16.3 litres of strike water at 74°C as I wanted a mash of 64°C as I wanted to finish with 20 litres of 1.069 wort. After the boil, I checked the gravity with my refractometer and it was reading at 1.060. Something’s wrong here. I double checked with 2 different hydrometers, and I also checked the calibration of the refractometer. They all read true, it was 0.009 lower than desired. This is quite a lot when dealing with gravities. This meant that unlike the last 10-15 brews where I got 70% efficiency, this was sadly running at 61%.

I was racking my brains for what I’d done wrong. I re-visited all the calculations, checked the sheet, I honestly couldn't see what I’d done wrong.

Remember, that this was happening whilst I was doing a second brew of an IPA made with Amarillo, Centennial, Chinook, and Exp. 366 (bittering done by Galena). For this, I was using 6.21 kg of malts into 15.5 litres of strike water, again at the “rule” temp of 74°C strike water to get a final 22.5 litres of 1.059 wort. I performed the brew as I've done so many times before, I recirculated about 3 times (in case the mash extraction had been the problem) and it seemed to go well.

Until I cooled and checked the gravity. This time, instead of the 22.5 litres of 1.059, I got 22.5 litres of 1.050 wort.

By this time, I’m doing my nut trying to work out what the problem was. If I’d got any hair, I would have pulled it out. The only thing I could think that was different to the previous 22 brews I have done was that yesterday, in Manchester, it was pretty unnaturally warm.

I did manage to get to the logical conclusion regarding mashing temperatures, and strike water temperatures, etc.  I did a bit of research and came across a whole load of websites that have various strike water calculations on them (I’ll let you Google them). Enough that I started to wonder why I’d never looked into this before, but the reason was simply that in the past, it’s worked for me how I did it.

The bit that got me was “To calculate the required strike temperature to achieve your desired mash temperature, the following equation can be used (adapted from “Brewing”, M Lewis and T Young, Aspen Publishers Inc, 2001, pg 102):Strike Temp =desired mash temp x (litres water + (0.4 x kg malt)) – (0.4 x kg malt x malt temp) / litres water”

I put this into my brewsheet and measured the temperature of the grain, it is at 25°C (remembering that my house was about 13°C only 3 months ago, this is a massive increase). This when put into the brewsheet with the new equation gave me a strike water temperature of 67.92°C, to get a mash temperature of 62°C or 70°C to get a mash temp of 64°C.

As a note, I've found that I start to get terrible extraction efficiency from doing mashes too warm, thus why I mash for longer at lower temperatures. This does have a knock-on effect that I end up with higher attenuated beers which means they can be more alcoholic, and less residual sweetness. But I’m usually fine with that.

So, these new, lower strike temps are quite a bit lower than the 74-75°C I usually mash at. This, with the above note, would probably explain when I got such awful efficiency yesterday.

I then manipulated the calculation to let me know the mash temperature yesterday, with the grain being so warm, and it seems that I was mashing at about 67.25°C. This is at the upper end of what’s fine for mashing, but I've always had problems at that end of the scale with efficiency.

So, take it from me, and my learning curve way to brewing, the strike temperature is another variable to add into the mix, and one that can have drastic effects on the way your brew goes.