Definition: Filtering

A process for clarifying wine by removing suspended particles by passing it under pressure through filters. Excessive filtering of wine can deprive it of many of its qualities. Clarification by fining, which is less stressful for the wine, is practised by many winemakers who are keen not to weaken the wine's potential. The different filtration processes are: sieve filtration, through which particles larger than the pores of the filter are retained. Adsorption filtration, in which the adsorbed particles are retained and fixed to the filter by an electrical phenomenon. Continuous alluvial filtration is a combination of the two previous principles, in which the wine is first thoroughly mixed with fine diatomaceous earth (Kieselguhr) and then passed through the filter. This process has the advantage of clogging the filters less quickly and improving the flow rate. The degrees of filtration, in ascending order, are expressed as coarse filtration, fine filtration and sterilising filtration. Very tight filtration is subject to criticism today, based on the principle that if the wine comes out very bright, it is impoverished and diminished. Syn.: filtering.