Cloudiness in Beer
Cloudiness in beer has several main causes. For some styles of beer, such as a witbier, it is desirable, and for others, it is regarded as a flaw. It is, therefore, important to understand what factors influence clarity and cloudiness of beer so that you can control the appearance of your beer as best possible.
1. Suspended Proteins
Suspended proteins usually make a beer look dull and ugly, regardless of style. Proteins in beer can contribute to chill haze, in which cooling the beer to around fridge temp drives proteins out of solution, creating lumpy clouds that disappear as the beer warms.
The hot break and cold break are important parts of the brewing process. The hot break is proteins coagulating as the boil begins to roll. The cold break, which drives even more protein out of suspension, happens as a result of rapidly cooling the wort after the boil.
These proteins settle to the bottom of the wort after it sits for only a few minutes, so it's easy to rack the beer into your fermentor and leave these proteins behind. Additives such as Irish moss or whirlfloc will also help to clear these proteins.
2. Unsettled Yeast
Yeast that has not flocculated, or settled, is generally the biggest factor in the clarity of homebrew. Some strains of yeast have been selectively bred to be more flocculent than others, so when choosing a yeast, check the level of flocculation of the yeast and compare that to how the style of beer should look.
Highly flocculent yeast will settle out after 3-5 days. These yeast are often so ready to become a cake of trub that they need to be roused to finish fermentation. Medium-flocculent yeast generally take 6-15 days to settle, but with enough time will settle out on their own. Yeast strains with low flocculaiton, such as hefeweizen and witbier yeasts, don't settle much with time. These yeasts will leave your beer looking cloudy - which is good for certain styles.
Yeast will also flocculate more after fermentation as the beer temperature drops, so if you can cool your beer in a basement or fridge during secondary fermentation, then you have a reliable method for making your beer significantly more clear. Using this method, you'll notice that after a week or two, the beer is much less cloudy, and that after the first 5-10 days, very little additional yeast drops out of suspension.
Beer that looks clear can still have up to one million yeast cells per mL, so for standard-strength beers, you don't have to worry about not having enough yeast left for bottling - it's still there. Whether or not it's healthy is another question, but generally repitching yeast for bottling is unnecessary.
3. Other particles
The most significant contributor here is hop particles. Hop debris tends to stay in suspension a little longer than yeast, and is particularly noticeable when dry-hopping a beer. As with yeast, giving a beer time on secondary at lowered temperatures is the best way to clear, although with beers that have massive amounts of hops, like double IPAs, cloudiness is just an expected byproduct - it might take longer to try to clear the beer than what the brewer deems best for beer flavor.
Any other ingredients that you add to your beer will influence color and clarity. Fruit tends to cloud beer, as some fruits leave pectin in the beer. Other additives may cloud beer, depending, obviously, on their color and how readily they settle.
Clearing your Beer
Again, the best agent for making your beer less cloudy is time. Over time, many of the suspended particles will fall out. Lowered temperatures will help this to happen more quickly. However, other things can be done to help make a beer more clear.
- Select malts with lower protein levels.
- Use more flocculent yeast.
- Add Irish moss or whirlfloc at the end of your boil.
- Use a fining agent like gelatin, isinglass, or polyclar.
- Filter your beer. This method, being the most challenging and costly, would be a last resort.