Tannin can be derived from a number of sources. This tannin powder is made from plants. It is also present in varying amounts in grapes (seeds, leaves and stems). It can be used to supplement wines and musts that are deemed tannin-deficient as well as fruit wines, which are usually deficient in tannins. Tannin aids in clearing the wine as well as helping to give wine its longevitiy. Tannin is often added to white wine before it is fined in order to aid in the clearing process.
Tannin powder is not readily soluble in wine and it is usually best to first solubilize it in a small amount of hot water which can then be added to the wine while stirring. Usual dose is 1/4 to 1/2 teasoon per five gallons of wine. Bench trials are recommended to ensure best results.