Chitosan is a commonly used fining agent, generally used in conjunction with Kieselsol.  The best fining agent for white wines. 

Chitosan is positively charged and Kieselsol is negatively charged. They are used in combination to avoid over stripping the wine. Leftover Chitosan particles bond with the Kieselsol and sink to the bottom of the fermenter as sediment.

Chitosan is derived from shellfish, so it is important to consider during the labeling process of wine, since there are people with shellfish allergies. Chitosan has also been reported to somewhat control Brettanomyces in the barrel.  

Kieselsol (available separately) is added first to the wine, and after an hour the Chitosan is added. This combination is especially effective on white wines.

The fining porocess works by creating both strong negative and strong positive charges in the wine, which allow for larger yeast clumps and faster clearing.

Directions: When fermentation is complete, rack wine off existing sediment. Add Kieselsol to carboy and gently stir. Wait one hour. Dissolve chitosan in 1 fluid oz/30mL of warm water. Add and stir gently. Clears wine in 12-48 hours. That is the big advantage, other clearing agents may take another month.  May not clear pectin haze or products made with hard water. For a 5-8 Gallon batch use a shot of each.  Don’t forget to put the Kies in first.