Bentonite is a clarifying agent used to clean up yeast and other stray particles by helping sediments drop out of the wine so that they can be easily strained out or simply left at the bottom of the fermenting vessel.
This agent covers a wide spectrum of hazes. It is a purified clay product which is especially good at adsorbing positively charged particles. It is the best agent for protein instability and it is easy to prepare. Its downside is that it leaves a fairly bulky lees. Normal use is 1 to 2 grams per gallon unless used during fermentation when up to 5 grams per gallon may be used.
It should be dissolved in hot water, then stirred into the batch to be treated. Settling will usually be complete within a week. Protein removal is best with lower pH wines and not as effective in high pH wines.