Do Beer Finings Kill Yeast?

Finings are added to beer during the brewing process to help prevent it from being cloudy. They work by attaching themselves to protein molecules and yeast cells, causing them to sink to the bottom of the brew kettle or fermenter.

Depending on the fining agents used, they are added either during the boil or in the fermenter after fermentation. New homebrewers are often concerned that adding finings may kill the yeast and prevent the beer from becoming carbonated.

Beer finings do not kill yeast. Some fining agents do cause yeast cells to flocculate and sink to the bottom of the fermenter, but there will still be plenty of active yeast present to carbonate the beer when it is bottled.

Photograph of Irish moss, taken to illustrate the article about whether beer finings kill yeast
Irish Moss

What makes beer cloudy?

One thing that differentiates homebrew from commercial beers is the fact that, with a few exceptions, commercial beers are usually crystal clear.

Although a little cloudiness isn’t a problem, most of us want our homebrew to look like the beer served in our local bar or pub. This can become especially important when sharing your homebrew with friends.

Cloudy, or hazy, beer is caused by three things: dissolved proteins, tannins and yeast.

Malted barley, and other grains used for making beer, contain protein which becomes dissolved in the wort. Dissolved proteins in the finished beer cause cloudiness; they also help maintain the head and make it feel less watery.

Grains like wheat and oats contain more protein than barley, which is why they are used to make naturally hazy beers such as NEIPA and Weissbier.

Tannins are present in grain husks. Although beer should contain some tannins, brewers usually try to avoid extracting excessive amounts of tannins into the mash because they can make the beer too astringent. Under some circumstances, they may also lock on to protein molecules causing cloudiness.

Yeast is an essential part of brewing and is responsible for turning the sugar in the wort into alcohol. Once fermentation is complete, the yeast flocculates, which means that it goes dormant and sinks to the bottom of the fermenter.

When bottling or kegging, homebrewers try to leave as much of the spent yeast and other debris behind in the fermenter. However, some yeast remains in suspension and is used to carbonate the beer naturally.

Once carbonation has taken place, the spent yeast slowly sinks to the bottom of the bottles or keg. At this stage, any yeast which remains suspended in the beer will cause cloudiness.

A bottle of Chimay Trappist beer from Belgium
Dark beers may not need fining

Are beer finings really necessary?

The use of finings to clear beer is mainly to improve appearance. Cloudy beer is perfectly safe to drink, and the haziness has little to no effect on the taste.

The only adverse effect that cloudiness has is on shelf life. Winemakers, who bottle condition their wine for several months or years, use finings for this reason. For most homebrewers, who will usually drink their beers within a few weeks, this isn’t usually an issue.

How do beer finings work?

Beer finings can be divided into two categories:

  • Fining agents which are added during the boil
  • Fining agents which are added after fermentation

Fining agents which are added in the brew kettle

Irish Moss

Irish Moss is actually a type of seaweed and is available either dehydrated or in tablet form.

Irish Moss has a small negative electric charge that attracts protein molecules in the wort, causing them to clump together and sink to the bottom of the brew kettle.

When the wort is transferred to the fermenter, the clumps of protein remain in the kettle along with the boiled hops.

Fining agents which are added after fermentation

After fermentation has taken place, the yeast naturally flocculates and sinks to the bottom the fermenter forming a so-called yeast cake which is part of the trub. Some strains of yeast flocculate more readily than others.


Commonly used to clear wine, isinglass is derived from fish and is added after fermentation has completed.

Isinglass binds to the yeast cells, improving flocculation and causing them to sink to the bottom of the fermenter. The isinglass doesn’t kill the yeast cells, and if you were to swirl the fermenter and add more sugar, it would start to ferment again.


Gelatine is extracted from the bones and skin of cows and pigs. Commonly used in cooking, it can also be used to clear beer and wine.

Like isinglass, gelatine is added to the fermenter where it locks on to protein molecules and yeast cells, causing them to drop out of suspension and sink. Once again, gelatin doesn’t kill the yeast; it just makes it clump together and sink.

Other fining agents

Several other fining agents are available, all of which are added to the fermenter before the beer is bottled. Sold under brand names such as Super Kleer, Polyclar and Bentonite, they all work similarly, by causing protein molecules, yeast cells and tannins to bind together and drop out of suspension.

How can I clear my homebrew without finings?

Most commercial breweries filter their beer, making it crystal clear. Although filtration isn’t usually an option for homebrewers, there are several other things which can be done to reduce cloudiness.

Use a wort chiller

When beer is cooled down quickly at the end of the boil, a so-called cold break occurs, causing proteins and tannins to naturally clump together and sink to the bottom of the kettle.

Take your time

It can be tempting to rush through the brewing process and drink your beer as soon as possible. Leaving the beer in the fermenter for longer allows more time for the spent yeast and other residues to drop out of suspension.

Similarly, if you wait a few weeks after bottling your beer before drinking it, more of the yeat will have settled on the bottom of the bottle.

Use more flocculant yeast strains

Some types of yeast drop out of suspension better than others.

Cold crashing and lagering

The easiest way to clear your beer is to store it in the refrigerator. Beer clears more quickly at lower temperatures as protein, tannins and yeast all come out of suspension.

Other considerations

If you decide to clear your homebrew with isinglass or gelatine, be sure to mention this when sharing the beer with your friends. Most vegetarians and vegans won’t want to drink beer made using products derived from animals.