Filtering verus clarifying?

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Filtering verus clarifying?

Postby chase » Sat May 05, 2012 4:40 pm

I was wondering if someone with knowledge on filtering and clarifying would be willing to do a write-up on comparing the two? That or link to an article that you know to be factually accurate.
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Re: Filtering verus clarifying?

Postby Anthony » Sun May 06, 2012 1:36 pm

In my mind, filtering is a way to clarify or clear beer. There are really probably two main ways to remove yeast and haze causing proteins from beer: mechanical and chemical.

Chemical processes of fining work on the basis that everything in suspension has some sort of an electrostatic charge. Yeast is negatively charged. Proteins are positively charged. You use a fining agent that is charged opposite to what you are trying to remove (unless you're using a binary regimen where you will employ both polarities). Things like gelatin, isinglass, egg whites, sparkaloid (DE), and chitosan are all positively charged. Bentonite and kieselsol are negatively charged. Typically the negatively charged agents are used in conjunction with positively charged agents because when yeast is left in suspension, they aren't as effective in removing the hazes. Once you combine one of these clarifying agents with your beer, you're essentially speeding up the clarification by increasing the particle size of what you're trying to remove so that it settles more quickly.

There are probably two main ways of mechanical clarification: Filtering and centrifuge. The mechanism behind the centrifuge should be pretty obvious, most homebrewers employ something very similar but much more primitive in their brew kettles. By quickly spinning the beer and drawing off from the right place in the whirlpool, you get clear beer. Filtering usually uses either some sort of cellulose medium or diatomaceous earth (DE, which if you remember from above is negatively charged) or both. The cellulose mediums work like sieve, trapping particles, the DE works by attracting particles as beer runs over it.

On the homebrew scale, only the cellulose filtering process is available (because DE is not only expensive but can be very dangerous if handled improperly). Filtering is usually done in a plate filter (using two plates, similar to what breweries do, except they use 10-25 times more plates and more surface area because they have more beer to run through the sieve) or in a water-filter housing sort of filter. I think the plate filters are probably more common because the filter pads are disposable versus trying to either reuse/clean or replace the more expensive water-filter housing spun filters.
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