What Is Wine Sediment? Tartrates, Lees and Tannin Explained

You pour the last glass from a bottle and something comes with it: a dark smudge of silt, a scatter of glassy crystals, a faint tan haze. Or you pull a cork and find its underside glittering like rock salt. The first reaction is usually suspicion. Is the wine faulty? Is that glass? Is it safe?

It's almost certainly fine. Wine sediment is the solid material that settles out of a wine over time, and nearly all of it comes from the grapes and the yeast that made the wine in the first place. It isn't a sign of a bad bottle, and it isn't dangerous. It can, however, make a good wine taste and feel worse than it should, which is why it's worth understanding what you're looking at.

Sediment comes in three main kinds, and they have different causes, different looks and different implications.

Tartrates: the crystals

If what you're seeing is crystalline (clear or white in a white wine, stained reddish-purple in a red, sometimes shaped like tiny shards of glass), you're looking at tartrates. Wine scientists call the most common form potassium bitartrate, or potassium hydrogen tartrate. You know it as cream of tartar.

Tartaric acid is the principal acid in grapes, and grapes also contain plenty of potassium. The two combine into a salt that dissolves happily in grape juice but less well in wine, because it's less soluble in alcohol, and less still in the cold. So when a wine gets colder than it has been before, in a cellar, a shipping container or your refrigerator, some of that salt crystallizes out. Producers have a cheerful name for the result: "wine diamonds," or Weinstein, "wine stones," in German.

Most mass-market wines are cold stabilized to prevent this. The wine is chilled before bottling (Decanter describes several days at around -5 to -10°C) so the crystals form in the tank and can be filtered off, sometimes sped up by seeding the wine with fine tartrate crystals. Many fine-wine producers skip or minimize the step on the view that it can affect flavor and structure, which is why tartrates turn up disproportionately in good bottles. Wines of Germany notes that they're most likely to appear in older, top-quality wines like Auslese and Beerenauslese, and high-acid, cool-climate whites in general are more prone to them.

Where you find them depends on how the bottle was stored. Decanter points out that a bottle stored on its side or upside down tends to collect crystals on the cork; one stored upright collects them at the bottom; and under a screwcap they gather at the bottom or float, since they don't stick to the closure.

There's a second tartrate, calcium tartrate, that behaves differently. According to the Australian Wine Research Institute (AWRI), it forms slowly, often months after bottling, and because cold has much less effect on it, cold stabilization doesn't reliably prevent it.

Are tartrate crystals safe? Yes. The AWRI describes them as an aesthetic defect with no detrimental effect on wine quality. Wine Spectator notes that potassium bitartrate is classed by the US Food and Drug Administration as "generally recognized as safe" and that the amounts in wine pose no risk. They're tasteless to many people and slightly tart to others, but nobody enjoys crunching them, so leave them in the bottle.

Could it be glass? Very unlikely. Tartrates are far softer than glass: pressed between the backs of two spoons, they crush to a powder, and they dissolve in hot water, which glass won't. They also tend to come in quantity, scattered across the cork or the bottom of the bottle, rather than as a single shard.

Lees: the haze

Lees are the spent yeast cells and fine grape particles that settle out after fermentation. In most wines they're removed long before bottling, by racking the wine off them (drawing the clear wine away from the deposit), then fining and filtering. What's left in a typical bottle is negligible.

Some wines keep a closer relationship with their lees on purpose. Muscadet labeled "sur lie" must, under its appellation rules, stay on its fine lees until at least March 1 of the year after harvest and be bottled straight off them. Lees aging adds texture and a richer, creamier feel; Wine Folly notes that the breakdown of yeast cells releases compounds we sense as extra body and flavor. Traditional-method sparkling wines age on their lees in bottle, and those lees are riddled into the neck and removed before the wine is sold.

Where you'll actually meet lees in the glass is in unfined, unfiltered and natural wines, and in pét-nats and other ancestral-method sparklers, which are often bottled with their lees and cloudy by design. Lees sediment tends to be pale, tan or grayish, and fine, more like a dust or a haze than a crust.

Tannin and pigment: the silt of old reds

The sediment most people mean when they talk about decanting is the dark, silty deposit in an aged red, and this one is made in the bottle, by time.

Red wine's color comes from pigments in the grape skins called anthocyanins. On their own they're unstable, so they bind with tannins to form chains, or polymers. As Kelli White explains in a piece for JancisRobinson.com, those chains keep changing length as the wine ages, and some grow too large to stay in solution and precipitate out. That's sediment. It's also part of why an old red loses its youthful purple and turns garnet and brick, and part of why it feels softer than it did in its youth: some of the tannin is now sitting at the bottom of the bottle.

This is why sediment tracks age. Wine Spectator's Dr. Vinny says he generally starts expecting it about ten years after the vintage, and the more pigment and tannin a wine starts with, the more it tends to throw. Vintage Port, bottled young, unfiltered and dense with color, is the extreme case: Taylor's describes a "crust" that grows more compact over time and partly adheres to the glass, plus translucent flakes known as "beeswing." Our guide to which wines throw sediment goes through the regions and ages in detail.

In practice, a red wine's sediment is a mix of all three kinds at once: polymerized tannin and pigment, some lees and grape solids that were never removed, and tartrate crystals stained dark by the wine. Sometimes the deposit doesn't fall at all. Jancis Robinson notes that some wines coat the inside of the bottle with a film that stays put however long you stand it up, but won't cloud the wine.

Is wine sediment safe to drink?

Yes. Wine scientists and wine writers are unanimous on this one: sediment is harmless. It's made of material that came from the grapes and yeast and was already in the wine. Wine Spectator does add one footnote, that sediment can be concentrated in spent yeast, which people with a yeast allergy may want to keep in mind.

Safe isn't the same as pleasant, though. Sediment is gritty, and it can taste bitter. The more interesting effect is subtler. Fine sediment suspended in the wine tends to coat the tongue, flatten the texture, mask aromas and shorten the finish, and it turns a brilliant wine dull and muddy in the glass. If you want to see this for yourself, our FAQ suggests a simple experiment: decant a sedimented bottle cleanly, then pour two glasses, one as-is and one with a little of the sediment from the emptied bottle stirred back in, and taste them side by side.

Sediment isn't a verdict on the wine

Sediment says very little about quality on its own. Dr. Vinny's view is that it's neither a sign of quality nor of poor storage, just a natural byproduct of making and aging wine. Port producers like to point out that a heavy crust shows a wine with body and concentration, and German producers will tell you tartrates are the mark of a wine that wasn't over-processed, but the most you can really say is that sediment shows a wine that was made to age, or was handled with a light touch, or both. A filtered wine with no deposit isn't worse for it.

What sediment can't tell you is whether a wine is faulty. A musty, wet-cardboard smell is cork taint, a sherried or vinegary smell in a wine that shouldn't have one is oxidation or spoilage, and a still wine that's unexpectedly fizzy and cloudy may have refermented in the bottle. None of those has anything to do with sediment, and none of them can be fixed by decanting.

What to do about it

Sediment is easy to deal with if you give it time. The whole game is to let gravity gather the deposit into one place and then separate the clear wine from it without stirring anything back up.

Start by standing the bottle upright, ideally the day before; the fine silt in an old red can take hours to settle, and our guide to how long wine should stand upright has the details. Check the bottom of the bottle with a phone flashlight to see what you're dealing with. Then pick a method. The traditional candlelit pour is free and works with practice, though some wine gets left behind and the pour aerates the wine. A basket suits fragile old Burgundy. Cheesecloth and strainers catch crystals and cork bits but let fine silt straight through. A siphon such as the Jory draws the wine out of the upright bottle through a stainless steel straw, without tilting it, pouring through the neck, or aerating it, leaving the sediment, tartrates and any cork bits behind. It takes about three minutes for a 750ml bottle once started, the bottle needs to sit higher than the decanter, and it's for still wines only. Each method is covered in our guide to decanting wine with sediment.

Don't forget whites. A Riesling or white Burgundy full of tartrate crystals can be decanted off them just as a red can be decanted off its silt, and a gentle method that doesn't add air is often the right choice for older whites.

Sediment is just something a wine leaves behind. Leave it in the bottle.