I have seen in a couple wine recipe that people say to add a cup of tea. Why would you want to do this? And would any of the long time folks actually suggest this? I did a forum search for "tea" and "tea bag" with no results.
Actually, that is a very good question. There are some grapes (reds) that have more tannin than others. When you ferment on the grape, when making a red wine, you don't have to concern yourself too much with adding tannin unless you desire more astringency. But, just as Julie mentioned, if you're doing a juice bucket it's a good idea to add some tannin because you don't have stems and/or seeds to add any tannin.
However, our North American cool weather grapes such as Concord and Niagara have very little natural tannin. It will help to balance these wines by adding a nominal amount of tannin--1/4 tsp per gallon. And nearly all fruit, except elderberry, has no tannin. So it's a good idea to add a nominal amt. to these as well. Tannin plays a partial role in clarification as well so for that purpose it's also a good idea. And adding tannin to wines that need it also stabilizes the color so you don't get plate-out of color in your bottles. The proper amt. of tannin in wine is often a neglected addition. Tannin comes from either grape or wood. Either one is OK. Tannin also comes from oaking, but is not quite the same thing as adding powder because you can't control the addition as well. We add tannin to everything where we know the tannin is naturally low.
3 gallons of Organic Old Orchard-Blackberry Lavender Lemonade, 2 gallons of Tree Top apple juice, 4 lbs of Kirkland frozen fruit mix of blackberries, raspberry, and blueberries, 12.5 cups of Kirkland organic sugar, Fermintis Safcider yeast, and wyeast yeast nutrient.
If you add 1/4 tsp per gallon, that would be a nominal amt. Don't over-do. Astringent wine is nasty. It incorporates the best when done during fermentation. But adding in the secondary is OK and you don't need to let it sit very long.