Last week we took a look at kettle finings, those potions and powders you zealously chuck into the boil in hopes that they’ll precipitate out the malt proteins that can create chill haze. Irish moss and Whirlfloc tablets do a great job of pulling proteins out of solution in wort, but what about the suspended yeast cells that remain in your beer after fermentation? Those can cause haze, too, after all.
Well, that’s where post-fermentation finings, or cask finings, enter the picture. As the names suggest, these are substances that brewers add to finished beer to encourage suspended particles, mainly yeast cells, to drop, producing brighter beer.
Professional brewers have access to a whole army of clarifying means and methods, including
- Centrifuging
- Filtering through diatomaceous earth or perlite
- Filtering through plates or other mechanical means
A few homebrewers clarify their beer through purpose-made filters, but cask finings are more readily available and easier to use on a small scale. The most commonly available cask finings are gelatin, isinglass, and polyvinylpolypyrrolidone (PVPP).
Gelatin
That’s right, the same stuff your grandma used to create those dreadful “salads” at Midwestern potlucks also drags yeast cells to the bottom of a keg or carboy. All you do is dissolve a teaspoon of the stuff in 2 to 4 ounces (59–118 ml) of water, heat the mixture to 150°F (66°C) or so (but not boiling!), add it to 5 gallons (19 l) of cold homebrew (the colder the better), and gently mix. Wait several days, and then rack bright beer into the serving keg or bottling bucket. Make sure to buy unflavored gelatin so as to avoid any artificially flavored cherry surprises when you tap the beer. Gelatin is, of course, not suitable for vegetarians.
Isinglass
Made from the swim bladders of various species of sturgeon, isinglass simultaneously clears your beer and renders it as hostile to vegetarians as gelatin. Traditionally used to clarify cask-conditioned real ales in the British Isles, isinglass is less common than it once was, although Guinness famously clings to the practice. Isinglass is available both as a prepared solution and as a powder. You can simply dump the liquid into your fermentor, but before use, the powder needs to be dissolved in water and pH-adjusted according to the directions on the package. Brewers who go through a lot of isinglass probably want the powder. Me? I just buy the pre-dosed liquid on those rare occasions when I use it.
Chitosan (pictured above), which is derived from the shells of shrimp and other crustaceans, is sometimes sold as an isinglass alternative, and the two may be used interchangeably in the brewhouse. Individuals who suffer from shellfish allergies are advised to avoid chitosan, however, so be sure to check the label before you purchase any clarifying agent.
Polyvinylpolypyrrolidone (PVPP)
Better known as Polyclar, this fining consists of lots and lots of itty bitty plastic beads that happen to carry a strong charge, making them very attractive to yeast cells. All you have to do is make a slurry of about 2 teaspoons of Polyclar with 2 to 4 ounces (59–118 ml) of sterile water, and add it to the beer. Let it hang out for a few days, and you’ll have vegan-friendly clear beer.
If you don’t like the idea of animal by-products or little plastic beads in your beer, then you’ll want to stick around for the third and final installment of “Clear Beer.” Next week we’ll take a look at a couple of other methods that can help you produce crystal clear homebrew: temperature crashing and fermentation enzymes.