The Facts about Fining Agents

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Fining agents are used to clarify wine and beer before bottling or long-term storage. Fining (pronounced fine-ing) agents work on the principle that all of the particles clouding up wine or beer have an electrical charge. As the saying goes, opposites attract, so a positively charged fining like gelatin will attract negatively charged particles and bind with them, making them too heavy to float. They will then sink to the bottom of your carboy, leaving everything brilliantly clear. Well, that's the theory. In practice, finings might not work on the first try or it may take more than one kind of fining to clear a wine or beer.


Bentonite is a fining agent. It not only improves a wine's appearance; it also makes sure that it is stable. Stable means that the wine won't change its appearance, taste, aroma or chemical composition while in storage. Bentonite is a type of clay, known as aluminosilicate, its technical name is Montmorillonite. It's found with various minerals attached to it, such as sodium, calcium and magnesium. It was originally found in Fort Benton, Wyoming (where the name came from). It's used in winemaking, beauty treatments, mineral extraction, water treatment, and kitty litter.

When used in winemaking, it is stirred into the wine to remove proteins and other haze-causing particles. It works through adsorption. This means that it attaches itself to a particle, and together they are too heavy to stay in suspension, falling to the bottom of the carboy, leaving the wine clear and stable. Bentonite settles out so completely that it does not leave any residue of taste or color behind.

Our wine kits have you add bentonite on the first day. This is one of the fundamental differences between kits that you may have noticed. The reasons behind it go beyond technology, straight into winemaking philosophy. When bentonite is added on the first day, it disperses through the wine and most settles to the bottom within a few hours. At the end of 48 hours, however, the bentonite is back in circulation. This is because of the process of gas nucleation that the CO2 in the wine is undergoing.

As the yeast ferments the sugar, it converts it into carbon dioxide (CO2) and alcohol. The bubbles of gas don't actually appear out of nowhere. They want to come out of suspension on some kind of a point, where a nucleus of gas can form the beginning of a bubble. Thus we get the term 'nucleation'. This point could be a scratch in the carboy, a bit of grape material, or a particle of bentonite. The bentonite is surrounded by a bubble of gas and floats up to the surface of the wine; when the bubble bursts, the particle of bentonite drops back down to the bottom of the carboy, all the time working to absorb the other particles clouding the wine. In this way, the bentonite is circulated around the wine continuously for days, doing its job.

When bentonite is added to a wine kit post-fermentation, it does not have the advantage of the CO2 lift that it would get during fermentation. Therefore the winemaker is obligated to stir it through the wine repeatedly, ensuring the thorough dispersal. In addition, because the bentonite will quickly settle out before it can effectively clear the wine, significantly more is needed when used post-fermentation. WineXpert kits typically use 10 or 15 grams of bentonite, while some companies use up to 80 grams! Not only does this amount cause the formation of a deep, loose sediment bed; it also has the effect of stripping the wine.

Finings are considerably more powerful than most people suspect. With a sufficient dosage of finings it is possible to strip a red wine to the point where it becomes 'white'. Too much finings can lead to a stripping of color and flavor, making it necessary to formulate much darker and stronger wine kits to compensate. By adding bentonite on the first day, the formulation can be much closer to the desired finished wine, without extra additions or manipulation. Although it may seem a little odd to be adding clay to your wine, when the finished product is clear and delicious, you'll be glad that there was a little bentonite to polish it up.

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