Filtering wine is used to remove residues and solid parts: here's how and when to do them correctly.

The complete guide to proper wine filtration

In assessing the quality of a wine, clarity plays a key role: in fact, the absence of turbidity makes it possible to recognize a fine wine even without uncorking the bottle. It is the result of careful wine filtration and clarification carried out by master vintners through a meticulous and gradual process that requires several stages.

Understanding how to filter wine, what techniques are commonly used in the most renowned wineries, or witnessing in person the wine-making processes through a guided tour at a historic winery such as Banfi, may be a great way to expand the knowledge of the world of wine for our visitors.

How to filter wine and why

Filtering wine, red or white, is done to increase the clarity of the product by removing suspended elements that can cloud its appearance or, in some cases, compromise its quality and bouquet of aromas.

Basically, wine filtration involves separating the liquid from solid residues (lees, yeast or other grainy particles) that may remain at the bottom after pressing or fermentation. This procedure is carried out with the use of special filtering tools, made of different materials and often enriched with substances that increase their filtering capacity.

Wine filtration techniques

The different filtration techniques, depending on the grain size of the particles to be removed, are divided into:

• Coarsening filtration techniques: these are used to remove the more voluminous particles in suspension in the wine;
• brightening filtration techniques: they work on the smallest particles, those visible especially in white wines or fine productions where even the smallest sign of turbidity can compromise the quality of the product;
• sterilizing filtration techniques: they completely eliminate microorganisms in the wine, including potentially harmful yeasts, thereby stopping the fermentation process at its ideal point.

The methods used when filtering wine

Speaking of how wine is filtered, it is interesting to know that in large wineries, there are two main methods of intervention:

• the first is called sieving or surface filtration: it involves filtering the wine through a series of porous surfaces that retain impurities on the surface, since they are larger in size than the filter holes;
• the second is called absorption or depth filtration: it involves the use of absorbent fibers that retain sediment and particles within them, thus allowing only the now-brightened wine to filter through. 

Thus, there are different wine filtration techniques that also differ in the type of materials used during the process. The choice of filters depends mainly on the characteristics of the wine and the degree of clarity you want to achieve. In addition, wine filtration techniques can be performed in sequence to achieve satisfactory clarity depending on the wine being treated.

Deposit Filtration

Deposit filtration is the first to be performed and has a coarsening effect. In fact, its purpose is to remove the coarser particles through the use of a cloth. This is one of the most widely used methods to filter wine at home.

Flood filtration

Continuous flood filtration cleans the wine of fermentation sediments (lees, skins and yeasts). A perforated panel with rather large pores is used. They are filled with cellulose and silicates, materials that activate and intensify the filtration process.

The advantage of this method is that it can work on large quantities and take full advantage of the effectiveness of filtration aids.

Filtration on cartons

Filtration on cartons is through biodegradable and compostable cellulose panels enriched with cotton fibers, kieselguhr, and cationic resins. Panels are sandwiched between two perforated sheet plates, and the depth filtration is used: the cartons thus absorb and retain major impurities.

Filtration on membrane

Membrane filtration (or "microfiltration") is for wines that must meet a high degree of clarity requirements. Very thin membranes capable of retaining microscopic particles are used, made of both organic (polymeric membranes) and inorganic (ceramic material membranes) materials.

Finally, when the liquid flow is parallel to that of the membrane and minimizes deposits on the membrane, it is called tangential filtration.