27 of November, 2025

What is Wine Clarification and Filtration?

15 Bodegas Editorial Team

Wine is not a simple beverage — each bottle is the result of a painstaking process that combines nature, science, technology, tradition, and human skill. If you're a regular reader of our blog, you know that one of our favorite topics at 15 Bodegas is teaching you the ins and outs of winemaking. This time, we want to delve into two processes that guarantee the quality and stability of each bottle: wine filtration and clarification. Will you join us?

What is wine clarification?

Wine clarification is a technique used in winemaking to remove suspended particles that can affect the wine’s appearance, texture, and stability.

These suspended particles are a natural end product of the winemaking process. During fermentation, wine develops certain impurities, such as yeast and bacteria. These unwanted companions cloud and dull the wine. To prevent this, winemakers create methods of wine clarification. This results in a much cleaner, brighter, and more balanced beverage.

Wine clarification is a tradition dating back millennia. It was already widely practiced in ancient Rome. Clarification is an optional step when making wine. Some of the natural wine producers skip this step for customers who enjoy the result of a wine’s natural sediments. However, it is advisable to subject the wine to this process for several reasons:

- Prevent particles from altering the wine's organoleptic characteristics. This is not only important to preserve the aromas, color, flavor, and nuances of the beverage but also to ensure that these sensory defects do not devalue the wine’s market value.

- Eliminate harmful compounds. Clarifying agents reduce the content of components, such as ochratoxin A (OTA), that could be harmful.

- Create a more attractive product. Suspended solids cloud the liquid, which can be unpleasant or unappealing.

- Make the wine more stable for bottling.

- Improve the mouthfeel.

How is wine clarified?

There are various methods of clarifying wine. The method depends on the type of wine desired and the producer's philosophy. Along with filtration, clarification is one of the final stages of winemaking—it occurs just before bottling. Below, we'll explain the most common clarification methods.

Natural or Spontaneous Clarification

For this method, only gravity is needed. The wine is left to rest in vats, barrels, or tanks depending on the type of wine barrel so that the force of gravity can act on the suspended particles, which accumulate at the bottom over time.

Although some winemakers are satisfied after this natural clarification, it is not enough to completely clean the wine. Therefore, most producers clarify their wine a second time, leaving an impeccable result.

Clarification with Clarifying Agents

Typically, the clarification process involves adding substances to wine that quickly and effectively remove impurities. Among the many options available, these clarifying agents can be divided into three main groups: protein-based, mineral-based, and synthetic.

Protein-based agents include substances of animal origin, such as egg white, milk casein, calf blood, or gelatin, which can be derived from pork or fish. Clarifying wine with egg white is one of the most prestigious and traditional ways of doing this. In fact, its origin dates back to the 17th century, and it is primarily used to clarify red wine.

Among the mineral-based clarification ingredients, bentonite stands out, a clay used in both white wines and red wines. Another common ingredient is silica gels, which are often added to act together with gelatin to clarify wine.

The third and final group consists of more modern alternatives, which are not as widely used as those listed above. Among the synthetic agents is PVPP (polyvinylpolypyrrolidone). This is a type of glue capable of, among other things, reducing astringency in young red wines.

In addition to those already mentioned, there is a fourth group: plant-based fining agents. This category includes alginate, a substance extracted from brown seaweed; it is very common in avant-garde cuisine as a gelling agent and for creating spherifications. Alginate is often used in sparkling wines.

Note that there are regulations regarding the fining agents permitted by each Designation of Origin.

What is Wine Filtration?

We've already seen what wine clarification entails, and now it's time for filtration, which is the final step to achieving that clean, sparkling elixir we desire.

Wine filtration is the process by which the solids that have separated after adding the clarifying agent are removed. The wine is passed through a filter capable of retaining these particles and separating them from the liquid. Filtration must be carried out with extreme care, as excessively aggressive filtration can lead to a loss of the wine's unique characteristics and diminish its intensity and personality.

As with clarification, not all producers choose to carry out this step. When we come across an unfiltered wine, it's normal to find a large amount of lees and tartar. This is fine; they are completely natural and harmless materials. The only downside is that they can hinder the tasting process. However, to get rid of them, you can use a decanter to filter the wine at home before drinking it.

What filtration methods are used with wine?

There are multiple methods for carrying out the filtration process. The three most relevant are listed below:

- Earth filtration. Layers of earth composed of diatomaceous dirt or perlite are used, which are capable of absorbing impurities in the wine.

- Plate filtration. Here, several cellulose surfaces with varying degrees of porosity are used as a filter. Besides being the most widely used method, it is the least aggressive.

- Membrane filtration. This is used in more advanced stages to eliminate finer particles and microorganisms that could alter the stability of the wine. In this case, the wine is passed through membranes with microscopic pores that act as a sieve.

What is the wine filtration process?

We've already seen the techniques, but how is the wine filtration process carried out? Typically, it takes place in three distinct phases. However, these are not independent actions; each undoubtedly impacts the next. Therefore, it must be understood as a comprehensive and complex process. For a satisfactory result, careful selection of the technology and the types of filters to be used must be made, along with rigorous monitoring of how the process unfolds.

1. Pre-filtration. As its name suggests, this is the step before filtration and involves removing larger particles that could interfere with subsequent stages of the process. It is not mandatory, but it is recommended.

2. Finishing filtration. The wine is then passed through cooling equipment to eliminate any microcrystals that may remain in the liquid. Plate filters are typically used for this step, providing finer, wine-friendly filtration.

3. Sterilizing filtration. In the final stage, sterilizing membranes are used to further stabilize and clean the wine before bottling.

As you can see, without proper wine clarification and subsequent filtration, it would be impossible to enjoy a clean, stable wine full of nuance. These steps ensure that every bottle reaches your table in perfect condition. And if you'd like to see how this entire process comes to life, at 15 Bodegas we invite you to visit our wineries and discover firsthand how we approach clarification, filtration, and every stage that shapes our wines. It’s the perfect experience to understand each detail before continuing to enjoy our selections in our online store.