Visit the Pencil & Spoon site

Filtrationis one of the things which I never understood before I got to see it happen afew days a week. As I didn’t understand it, I say it as a bad thing, somethingonly the big breweries did as part of their flavour-reduction mission, but Iwas wrong.

Thisis the filtering process I know (there might be other ways of doing it):unfiltered beer from the tank mixes with kieselguhr, a diatomaceous earth(which Wikipedia explains better than I can). The kieselguhr catches the yeaststill left in the beer, clumps it together and this then gets left behind on agentle plate filter (you can choose how fine or coarse you want the plates tobe) which the beer passes through. So it goes in cloudy and comes out clear andthe process is there just to remove the haze. But it’s about the flavour andthat’s important.

Filtrationinevitably removes flavour as it passes through the filter, but what is leftbehind is just yeast so what you find is that the flavour changes, the bodychanges and your perception of the beer changes. I can give the three examplesI know: a lager, pale ale and wheat beer.

First,the one that’s unfiltered: wheat beer. It’s all about the yeast in the beer andyou can taste and feel it when you drink: it’s got a fullness to it, a fatness,a juicy roundness. The yeast is there to give texture, flavour and aroma – it’svery different when it’s not cloudy and it becomes drier and crisper, lackingthe creaminess that you want from wheat beer. The beer is tastiest cloudy.

Lageris the best way of showing filtered beer: unfiltered it has a rich fullness toit, a rounded flavour profile, a softness; filtered it becomes dry, crisp andsharp. Lager should have a snappy finish to it and so filtration is key to getthat refreshing quality (though I do totally adore unfiltered lager, it’s justa different drink to the filtered stuff). It’s similar with pale ale: you wantthe hops to be bold but in unfiltered beer you’ve got other stuff softening thebitterness and wrapping it in the roundness of yeast. By filtering you take theroundness and make it sharper. It’s like a sentence which ends with a dash or onewhich ends with an exclamation mark.

Thenthere’s fining. Have you ever seen a pint of isinglass – the dried swimbladders of fish – before they go into a cask? The first time I saw it I almostposted back my CAMRA card. I’m okay with knowing that there’s something in mybeer which makes it clear, but it looks like a pint of body fluid and makes methink of a story my mate Matt often tells: he was on a big night out and one ofthe group was sick into his pint glass. A bit later he was back drinking fromthe same pint: “It’s ok,” he said, “it’s sunk to the bottom.”

Drinkersdon’t want opaque beers. Every beer is different: some styles are betterfiltered, others are better unfiltered, some work best with isinglass pullingthe yeast to one side (though only in cask beer). Sometimes I want my lager tobe unfiltered but it’s doing a different job to if it’s the crisp andrefreshing filtered version; the flavour changes, the body is different, thebeers are different, but both are good.

Filteringisn’t beer’s F-word.