What the heck is "Fining?"

Wine before fining.

In wine-making, fining is the process where a substance (fining agent) is added to the wine to create an adsorbent, enzymatic or ionic bond with the suspended particles, making them a larger molecule that can precipitate out of the wine easier and quicker. Given enough time many of these suspended particles would gradually precipitate out on their own.
White wines are fined to remove particles that may cause the wine lose color as well as removing heat-unstable proteins that could cause the wine to appear hazy. Red wines are fined for the same reason but also for the added benefit of reducing the amount of bitter, astringent tannins which makes these wines smoother and more approachable sooner after bottling and release. Ancient fining agents, such as dried blood powder were used, but today there are two types organic compounds and solid/mineral materials.

Organic compounds used as fining agents are generally animal based, which may bring concerns for a vegan diet. Most common organic include egg whites, casein derived from milk, gelatin and isinglass obtained from the bladders of fish. Solid materials can also be used as fining agents with bentonite clay. Activated carbon derived from charcoal removes some phenols that contribute to browning colors as well "off-odors" in the wine. Other inorganic materials use include silica and kaolin.

Some countries require the use of fining agents that may be an allergenic substance to appear on the wine label, as there may be trace amounts of the substance still in the wine. However a study conducted by the UC, Davis Department of Viticulture found that no detectable amount of inorganic fining agents.

As with filtration, there is the risk of some loss of flavor with fining with desirable flavor molecules going out with undesirable particles. Production processes get as much flavor and aromatics from the phenols before they are removed. Fining is considered a less harsh process than filtration.