Filtering a wine should only be undertaken as a last resort. Most wines will clear naturally if given time, or if there is the knowledge to assess the reason and apply the remedy, and there is also the fining method. It is therefore a very small minority of wines that need to be filtered. There is no doubt that filtering does take something out of the wine apart from the debris, and whether it fully recovers is open to doubt. The last few years have seen great strides in the marketing of filtering aids. Up to that time there was only the filter paper and an open funnel, and this left the wine in constant contact with the air for lengthy periods with the obvious risk of oxidation. Recently manufacturers have given considerable thought to the subject, and as a result a number of methods can be used. Any filtering system which allows the minimum amount of contact with the air must be preferable. The aim of filtering should be to clear the wine, and if possible to eliminate the remaining yeast cells and avoid the possibility of a secondary ferment. A filtered wine should be left in bulk for a while in order to give it time to recover.