Fining has been used for hundreds of years, and involves the addition of material that will interact with the colloids present in wine.

If another colloid with the opposite charge is added to the young wine, the opposite charged molecules attract each other (flocculate) and form a precipitate which can be removed either by allowing it to settle or by filtration.

The above diagram is by David Bird MW from “Understanding Wine Technology”

This removal of colloids cannot be achieved by filtration alone because the colloidal molecules are too small to be retained by the finest of filters. Fining can:

• Remove colloids in the wine and make it more stable
• Remove small particles in the wine and make it clearer
• Change the organoleptic properties of the wine: appearance, aroma, flavour.

Often a fining agent will do all three of these functions.