Roger C. Bohmrich, Master of Wine
July 2019

Fining and filtration are just two procedures carried out in the cellar which share the aim of rendering wine clear and stable. In any discussion about technical procedures such as this one, it is important to lay out definitions with care. The core principle holding that young wine should be free of visible particles and haze seems sensible and is appreciated by a large majority of drinkers. If that is true, why exactly do fining and filtration seem to disturb some people? There are many other tools a winemaker may bring to bear which might be more damaging, yet most remain largely hidden from view. The twin “evils” of fining and filtration, on the other hand, have become lightning rods for some in the wine community. The truth is that there are both pros and cons to many procedures which “adjust” the condition of a wine. As Paracelsus, a Swiss physician, observed in the 16 th century: “The right dose differentiates a poison and a remedy” (www.sustainable-nano.com). Or, in the context of this discussion, how a procedure is carried out determines its potential benefit or harm – and not necessarily the action in and of itself.

Oenology textbooks separate the concepts of clarification and stabilization (Jackson, 1994). To a lay person, the two share the same fundamental aims: achieving wine which is clear to the eye and protected from undesirable changes in bottle. Among the procedures to insure stability, dropping the temperature of a white wine near its freezing point, to precipitate potassium bitartrate, is a common operation. This illustrates the tension between positive and negative consequences. It might be argued that cold stabilization could bruise a wine as much as fining or filtration. It is done to avoid formation of (entirely harmless) crystals, which consumers tend to find alarming, later in the bottle.

Taking actions to remove yeasts and bacteria are typically viewed as assuring stability (Webb, 2015). This is of particular importance for white wines with unfermented sugars, which are inherently more vulnerable. The remedy likely involves sterile filtering through a membrane with pores of 0.45 microns, which captures all but 0.1% of those microbes. Other forms of stabilization address the possible formation of haze from unstable proteins or polysaccharides. Consequently, it would not be unreasonable to see clarification and stabilization as overlapping functions with common elements.

Fining is hardly a recent technique; it has been in use for centuries. The idea at its core is a simple one. For most of wine’s early history, the usual way to remove deposits after fermentation was to allow the wine to rest, undisturbed, and wait for gravity to do the work. After a period of time, the wine could be carefully decanted – or racked in today’s parlance – from the vessel holding the sediments to another, clean container. This sort of static settling is still in use, primarily as the initial method of removing large particulate in tank. For those few wines which are matured in barrel for extended periods – years, not months – and racked once or twice annually, such as traditional Rioja, the resulting wine is free of visible particulate. A traditionalist such as La Rioja Alta says: “Every six months, we manually rack every barrel under candlelight. It is an art to enhance the development of the wine, removing sediments in a natural way and monitoring each barrel individually” (www.riojalta.com). This is the gentlest way to clarify wine while simultaneously realizing the many benefits of barrel aging. It is undoubtedly less disruptive than centrifugation, which involves rotating at high speeds.

Today, fining is understood to mean the addition of a processing aid – clays or proteins in various forms – which will serve to attract and remove soluble substances, colloids in particular, while the wine is in tank or barrel. Unwanted tannins and proteins are the principal targets. Modern fining is a shortcut which also assures a more perfect outcome, yet not without possible alteration of the wine. For white wines, it is the norm. Transparency and brilliance are expected of whites by today’s drinker. Only a handful of so-called natural producers are bold enough to bottle white wines which may be cloudy and orange in color.

The materials employed for fining might be viewed narrowly as additives; but if there is no detectable residue in the finished wine, is that characterization accurate? The practice does nonetheless complicate the question of ingredient labeling. Many health-conscious consumers want to know what added chemicals or ingredients are present in bottled or canned drinks and foodstuffs. Opinions differ as to whether this should include foreign substances which pass through wine and do not leave noticeable remains. Some may seem at best peculiar or, worse, threatening and harmful. For example, carbon as charcoal may be employed to remove browning. A synthetic, polyvinylpolypyrrolidone (PVPP), serves the same purpose.

In this time of vegetarians and vegans, questions are raised as well about common fining agents which are derived from animals: albumin as egg whites; casein (milk); isinglass, from the swim bladder of sturgeons; and gelatin, from fish or meat (Harbertson, 2009). In the European Union, allergens must be identified on the label if they exceed the detection limit. EU regulations cite eggs, milk and sulfites but exempt isinglass for fining wine and beer (EU Regulation No 116/2011). These concerns are reportedly influencing winemakers to rely increasingly on bentonite, a clay, as a primary fining aid (Webb et al., 2015). In the current climate, producers seem to want to play it safe with respect to health-related issues which might, at the very least, result in bad publicity.

Fining involves practices which could be alarming to drinkers, whether warranted or not. Yet, it is filtration which has arguably attracted the greatest attention, perhaps because the basic concept is easy to grasp. Unlike fining, filtration is “the physical retention of material on, or within, a fibrous or porous material” (Jackson, 1994). The two main strategies are depth filtration through diatomaceous earth (DE) or cellulose pads and surface filtration through a membrane of plastic polymer (Bird, 2015). One variation of the latter is cross-flow filtration. The late Tim Patterson, a wise voice in all matters of winemaking, wrote: “The vast majority of wine in the marketplace, even at the very high end, goes through one kind of filtration experience or another…” (Patterson, 2007). White wines are nearly always filtered. For those which have residual sugar and/or have not gone through a malo-lactic fermentation, so-called sterile filtration is standard to prevent trouble in bottle. Such membranes are not sterile in medical terms, yet they have pores small enough to capture offending yeasts and bacteria (Bird, 2015).

Whether or not to filter reds, Patterson says, is a tougher decision. There is generally “more opportunity for microbial mischief” from spoilage yeasts, notably Brettanomyces, and lactic acid bacteria such as Pediococcus. Emile Peynaud, a highly influential oenologist and consultant, helped shape modern Bordeaux. In his book, Knowing and Making Wine, he left no doubt that he saw overwhelming benefits from filtration. Suggesting filtering strips wine of desirable components, he argued, “would mean conceding that the foreign substances in suspension and the impurities that form the lees, which filtration is precisely designed to remove, have a favorable taste function” (Peynaud & Spencer, 1984). Even sterile filters, Patterson notes, allow virtually every compound responsible for color, aroma, flavor and mouthfeel “to sail right through” (Patterson, 2008).

Yet, to some audiences, “unfiltered” seems to imply pure and unadulterated. The word can be found on labels (Fig. 1 & 2) in English or French (non filtré). In the eyes of devotees, such wines are perceived as genuine – the antithesis of technological. The implication is that their intrinsic qualities have been safeguarded by hands-off winemaking rather than diminished by unnecessary intervention.

Figure 1. The label of a red Loire wine from Bernard Baudry stating vin non filtré (unfiltered wine).

Figure 2. The front label of a Rhône Valley wine from Domaine la Bouïssiere stating both unfiltered and non filtré, its French equivalent.

In a roundtable discussion (Cutler, 2007), Christopher Howell of Cain Vineyard and Winery said: “I believe there is always something lost for what is gained.” Stefano Migotto of Winetech, a filitration specialist, fell in line with Peynaud: “We have performed a series of blind tastings using the same wine before and after filtration. The filtered wine comes out best, all the time.” Howell countered, saying “unfiltered wine just seems to be more complete.” There is clearly an emotional dimension to this discussion; filtering is not, as one might expect, simply a technical matter.

A small coterie of “handmade” wines goes even further, claiming to be both unfined and unfiltered. A few producers who fall in the “natural” school see this as a badge of honor (Fig. 3 & 4).

Figure 3. The front labels of Donkey & Goat wines from California proclaim “unfined, unfiltered” even for Chardonnay. Labels courtesy of Donkey & Goat.

Figure 4. The back label of a certified organic and biodynamic wine from France stating non collé (unfined) and non filtré (unfiltered). Label courtesy of Fabien Jouves.

The debate about clarification does not seem to have moved very far in recent years. It is safe to say that the vast majority of wine worldwide is subjected to fining or filtration, if not both. To all but a few drinkers, this then is a purely academic discussion. On the other hand, for a certain number of winemakers and their devoted clients there is a sincere belief that the finest wines – reds in particular – should be handled as gently as possible. For both commercial and philosophical reasons, this tends to pertain to small, handcrafted lots rather than larger-volume bottlings. Is the fuss over fining and filtration really warranted? Perhaps, but only if the techniques are severe, which is an exception rather than the norm.



Bird, D (2015), Filtration, The Oxford Companion to Wine, Oxford University Press, New York, NY.

Cutler, L (Jul 2007), Winemakers Discuss the Truth, Fiction and Consequences of Filtration in Winemaking, Wine Business Monthly.

European Union (15 October 2011), REGULATION (EU) No 1169/2011 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL, Annex II, p. 36.
Click here to read

Harbertson, JF (Aug 2009), A Guide to the Fining of Wine, Washington State University, WSU Extension Manual EM016.

Jackson. RS (1994), Wine Science-Principles and Applications, ©Academic Press, Inc., San Diego, California.

Patterson, T (Oct 2008), If Filtration ‘Strips’ Wine, What’s Getting Stripped? Wines & Vines.

Patterson, T (Jul 2007), When to Filter, Wine & Vines.

Peynaud, E & Spencer, AFG (1984), Knowing and Making Wine, English translation ©John Wiley & Sons, Inc.

Webb, AD, Harding, JE, Bird, D (2015), Fining, The Oxford Companion to Wine, Oxford University Press, New York, NY.

Webb, AD (2015), Stabilization, The Oxford Companion to Wine, Oxford University Press, New York, NY.

Click here to read. (accessed July 2019).