Filtering a wine before bottling is not necessary. A wine will clear on its own so long as the fermentation did not go afoul, and acid and pH are in good balance.
Fining agents can even be added to the wine to help the settling process to happen more quickly and thoroughly. For example, if you are making wine from a wine juice kit, normally it will come with bentonite. This will aid in clearing process. The wine will look very clear!
So if this is the case, why do wine filters even exist?
The one thing that needs to be understood about filtering wine with a wine filter is that it is not designed to take the visual cloudiness out of the wine. The filter pads are much too fine for this. They will clog up – usually within the first gallon. Time, gravity and fining agents will take care of the cloudiness. Filtering wine before bottling is done to add a polish to the wine – to add luster and brilliance. It is done to make the wine more beautiful, not less cloudy.
When you filter a wine before bottling you also are taking the last bit of wine yeast out of the wine. This amount of yeast is completely invisible to the naked eye. Doing this helps the wine to be more stable. If the wine is filtered with the finest filter (1/2 micron), it will be considered fermentation stable. By the way, a micron is very small. There’s about 400 of them across a period you find at the end of a sentence in a typical newspaper.
If you are on the fence as to whether or not to filter your wine before bottling, I would suggest comparing your wine side-by-side with a commercially made wine of a similar color. Almost all commercially made wines are filtered. See for yourself the difference then decide if filtering is something you would like to do to your wines.
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.