If you're looking for a benchmark wine to help you pin down that scratchy, mouth-drying black-tea astringency that wine tasters call "tannic," you'd be hard-pressed to find a more vivid example than the uncommon French grape that may actually take its name from the effect: Tannat.
Tannins, simply put, are complex organic compounds (known as "phenolics" in chemistry-speak) that occur naturally in grapeskins, seeds and stems and that impart a distinctly astringent (mouth-puckering) flavor in wine. A smaller amount of tannin may also be contributed by oak, particularly in wines aged in small, new oak barrels.
Because red wines are fermented with the grape skins while white wines usually are not, reds tend to be much more tannic than whites; and certain varieties are particularly tannic, including Cabernet Sauvignon, Syrah and Nebbiolo, for example, and the less-familiar Tannat.
Tannins are considered desirable because their anti-oxidant properties help preserve wine in aging. Over time in the cellar with ageworthy wines, tannins undergo a gradual chemical change called polymerization; astringency fades and the wine's flavors take on a more mellow complexity.
The same is true even of Tannat, but its natural tannins remain so prominently puckery that the wine gives us a serious remembrance of times past. Virtually all varietal Tannat on the market comes from two places: The Southwestern French region called Madiran (which usually adds Cabernet Franc and Cabernet Sauvignon to a Tannat-dominant blend); and Uruguay, a smallish South American country tucked between Brazil and Argentina, where 19th century Basque immigrants apparently introduced the grape and made it as much a trademark wine of the region as Malbec became in Argentina.
Looking for a completely different wine experience? Try Tannat.