Monday, May 31, 2010

How hot is that?

We've got a thermometer and we're not afraid to use it. In fact we've got a number of thermometers. Not one of them ever shows the correct temperature - I'm pretty sure - or if one does - it's an amazing coincidence.

The met office tells me that the temperature on Walney Island, which is where I did much of my growing up, is currently 14.3°C. Which seems quite parky. Which is why I've chosen to live a few miles inland (oh, and not in the middle of a windswept airfield). How accurate is that measurement? How precise? And what's the difference?

It's easy to use the terms "accurate" and "precise" as if they were interchangeable. They're not. Accuracy considers how near your measurement is to the true value, whereas precision tells us how close we can expect repeated measures made with the same instrument will be. I think. Unless I've got that the wrong way 'round.

So, if the met office is right (and here we mean right in a very godlike, absolute sense), and I went to Walney and measured 14.8, it would be fair to say that my accuracy was something like 0.5°C. If I made 4 more measurements really quickly (so as to be reasonably sure that the true temperature didn't change) and got 14.7, 14.8, 14.7 and 14.9, then I might say that my precision is something like ± 0.1

This all assumes that I've got a thermometer that reads tenths of a degree, i.e has a resolution of 0.1. If I take one of my crappy old glass thermometers with me ( I can judge the 1/2 degrees, just) I might end up reading 14.0, 14.5, 14.5, 14.0, 14.5. Which would be less precise, but more accurate .

Is any of this important to a brewer? There's one stage in the process where we're quite keen on getting the temperature "right" and that's in the mash tun. You'll be told that 65.5°C is the magic mash temperature (for a simple infusion mash). Of course, if you want drier beer you may aim lower (say 64°C) - for sweeter beers, perhaps higher (67°C ?). Whatever, we need to decide how accurate and how precise our temperature measurements need to be.

One thing we need to remember is that the mash tun is pretty big and has got a lot of stuff in it. For that matter, the mash tun is made out of a lot of stuff itself (which is why we generally preheat it in some way). We cannot make an accurate measurement of the mash temperature by simply sticking a thermometer in the middle and reading it. At the very least we'd need to make multiple measurements and take some kind of average - this is what we do - when shooting for 65.5, we generally get a range from something like 64 to 67, and the average usually works out OK. So we're reasonably confident that we're in the general area. At least at the top of the mash. Right after mashing in.

That said, what we're really after is nice beer. It's not really important that we mash at 66 rather than 65.5, so long as people like the beer and we get paid for it. But controlling the variability removes some of the potential for surprises down the line. This is why we use a thermometer with a resolution of 0.1°C (although 0.5 would probably be good enough, i.e. a good bit smaller than the range we measure), which we calibrate (to ~0°C) every now and then. We may not be very accurate, but at least we're fairly consistent in what we do. We hope that this helps the beer to be consistent also. And nice.

Friday, May 28, 2010

Why won't they brew strong?

"Why is it "traditional" English breweries won't brew anything stronger than 4.8%", it has been tweeted.

Taking a random selection of "trad" brewers -

Adnams: there's a couple of strong seasonals, currently "May Day" 5.0% ABV.

Cains: "FA" 5.0% ABV

Fullers: "ESB" 5.5% ABV

Hook Norton: "Haymaker" 5.0% ABV

Jennings: "Snecklifter" 5.1% ABV

Marstons: "Old Empire" 5.7% ABV

Shepherd Neame: "Bishops Finger" 5.4% ABV (bottle)

Thwaite's: "Double Century" 5.2% ABV (bottle)

Right, that's that canard shot and stuffed.

FWIW, we always have at least one stronger beer on. And, in fact, most proper brewers have (at least in bottle) a strong beer in their line-up, as well as their session beers.

I was talking with a local publican the other day - it's part of the job. He tells me that he has customers who come in straight from work at 4 or 5 pm, and drink 'til closing time (at least, I should think). Now I know this is a terribly déclassé drinking style, and must seem very strange to all you jaded urban sophisticates out there, but that's what happens in some pubs.

Anyway, he goes on to explain that this means that he takes 30 quid off them in a night, they have a lovely evening talking shite with their mates, and everyone is happy.

Furthermore, he points out, if he could get them to start on lovely 6.5% super-hoppy lovingly hand-crafted and challenging - whatever, they'd tilt after 3 or 4 pints. He'd take, at most, a tenner off them ('cos he's not going to charge a tenner a pint, is he?), and he'll turn his beer over at rate that would lead to wastage.

How do you like them apples?

Tuesday, May 25, 2010

The thermodynamic rollercoaster of beer.

Nothing's ever at the right temperature (or in the right place).

A brewery is a machine for making beer. Even a little Heath Robinson one like ours. One of the things that we have to manage is temperature. This has been preying on my mind of late since we've just had a spell of warm weather (at least that's what we call warm 'round here). Just for fun here's a not-to-scale graphical representation of this key process variable

See? It's a bugger, when you're not heating it, you're bloody cooling it. Inbetween, you're pumping it (or carrying it) from one place to another. God I love this job. Love it.

Sunday, May 09, 2010

Ass U Me

I notice that the good folk at the Reading BF list one of our beers as:
West Coast Blonde 4.4%
Pale beer brewed with West Coast USA hops?

Now, I know that they're very busy people, what with trying to ensure that their enormous range of 500 beers is in good condition (good luck with that), but why make up that bit about USA hops? Will it help sell the beer? Surely US hopping has become a real cliché in English micro-brews of late? I'm sure there's now a generation of drinkers who think that beer is supposed to smell like grapefruit.

For the record - there's only one beer in which we're currently using a US hop - and it's not this one. The contents of our hop store (it's a big chest freezer actually) include:

  • Northern Brewer - great quality - resinous and slightly citric, nice clean bitterness

  • Challenger - crisp bitterness, I find that some straw and grass comes through. Nice.

  • Hallertauer Mittelfrüh - also great quality - lightly floral, fresh.

  • Goldings - Used pretty much exclusively in our "milds". I've never really got on with Goldings (which must make me a weirdo)- there always seems to be a sort of cold stewed tea tannic quality if we use a lot of them in the boil. In a lightly hopped beer though, this works for me, while the bitterness may be quite low, the quality of the bitterness keeps it interesting.

  • Odds and ends of various "Styrians"

  • Bobek! Boss! Unlike the other "styrians", this isn't (I gather) a fuggle variant - has it got Northern Brewer in it's ancestry? Or something. Citric yes, but not grapefruit - it's orangey / lemony - tangerine perhaps.

  • Amarillo- Stinks of cat p*ss & mango. Revolting? But leave it to air for a few hours and the cat creeps out, then some distinct minty notes come through. Fascinating. The catty stuff doesn't seem to make it into beer either - but I'm inclined to let it breathe before using it for dry-hopping. The bitterness is good and all kinds of nice orangey tastes come through. Definite tropical fruit used late. Great example of how the smell of the hop in the hand is not what comes out in the beer.

And where did the "e" come from? It's blond, not blonde. It's the name of the beer, not the lady on the clip.