Tannins are an important descriptor for wine tastings and it basically refers to the dryness, bitterness, and astringency of a wine. It is most often associated with red wine and is the opposite of the sweetness found in many white wines. By no means are tannins a good or bad thing.

Tasting the Difference Between Tannin and Acid: Tannins taste bitter on the front-inside of your mouth and along the side of your tongue; Acid tastes tart and zesty on the front of your tongue and along the sides. Acid makes your mouth feel wet; Tannin makes your tongue feel dry.

Tannins are naturally occurring compounds that exist inside grape skins, seeds and stems. The scientific word for these compounds is polyphenols. The longer the skins, seeds and stems soak in the juice, the more tannin characteristics they will impart. This explains why red wines have stronger tannins than white wines.

How to describe tannins? Texture is useful to describe the quality of tannins, i.e. silky, plush or velvety. When a wine has a pleasant amount of tannins, noticeable but unobtrusive, it’s often described as “grippy.” When tannins are described as “green,” they’re slightly bitter and have unpleasant astringency.

In large amounts, tannic acid can cause side effects such as stomach irritation, nausea, vomiting, and liver damage. Regular consumption of herbs with high tannin concentrations seems to be associated with an increased chance of developing nose or throat cancer.

Tannins have also been reported to exert other physiological effects, such as to accelerate blood clotting, reduce blood pressure, decrease the serum lipid level, produce liver necrosis, and modulate immunoresponses. The dosage and kind of tannins are critical to these effects.

Although largely useful to the body, tannins also have negative effects. They are often anti-nutritional and can hinder digestion and metabolism, unlike polyphenols. Tannins can also help obstruct the blood’s absorption of iron, which may lead to many health problems.

Tea, like wine, contains tannin, and consuming it, especially on an empty stomach, can lead you to feel nauseated. Tannin is known to kill bacteria, and it’s a naturally occurring compound in tea––and especially potent in black tea––that results in that bitter tang.

While water affected by tannins does not pose any health or safety risk when consumed or used in the home, it can create some unique problems. Besides the unappealing color, affected water can have a plant-like, musty odor to it and will have an unpleasantly tangy aftertaste when consumed.

Tannins are gone when they no longer leech out of the wood. How long that will take depends on an assortment of variables, including the size of the wood, the type of wood, whether it was purchased from an LFS (sometimes pre-treated/leeched) or found in nature, etc.

Tannin can be removed from water with a carbon filter.

Just like steeping a tea bag in hot water, boiling driftwood in a large stockpot encourages more tannins to leach out faster, thereby shortening the curing process. Boiling the driftwood for 1-2 hours will sterilize the driftwood.

Driftwood does rot, but it’s generally quite a slow process. The wood in aquariums rots too, but, with the woods most commonly sold for the purpose, you won’t really notice much change unless you use them for years and years, unless perhaps they are very small to start with.

Tannins will leach out but the rate at which they leach out will drastically decrease the longer you boil the wood and the darker the water gets. So instead of boiling it for 35-40 minutes, boil it for 5-10 minutes, completely change the water and boil for 5-10 min again.

Soaking Driftwood We recommend you to soak it for one to two weeks. Soaking driftwood is important because doing so removes excess tannins. If the driftwood is not soaked beforehand, these excess tannins can otherwise darken or discolor the water of the aquarium.

Other media, such as Seachem Purigen, also remove tannins, but tend not to affect the ph of the water…so if you like a lower pH environment but are not a fan of the tint (gasp!), you’d be advised to use this media in place of activated carbon. It does eventually become exhausted, and may be regenerated if desired.

It can be difficult to completely remove tannins from a piece of driftwood. Activated carbon can help remove tannins from the aquarium water. Additionally a number of aquarists recommend Seachem Purigen for tannin removal.