What sediment actually is
Sediment is solid matter that forms inside the bottle as the wine ages, and it is mostly two things: tartrate crystals and precipitated polyphenols. Tartrates are salts of tartaric acid, which occurs naturally in grapes and crystallises with cold or with time. The polyphenols, meaning tannins and colour pigments, gradually join together as the wine ages and fall to the bottom.
It looks different from bottle to bottle. Sometimes it is powdery and dark, almost like soot. Sometimes it comes as small granules, or as translucent crystals that look like fragments of glass and are not. The colour runs from brick red to nearly black depending on the wine and its age.
It is common in structured aged reds: Barolo, Barbaresco, Amarone, Brunello di Montalcino, Sagrantino. You can also find it in younger wines made with little or no filtration, and a great many small producers choose not to filter precisely to keep the texture and detail that filtering strips out.
Does sediment mean the wine has gone off?
Almost never. Sediment on its own indicates no fault at all. What you need is to separate the natural deposit from the signals that do deserve attention: a musty cardboard smell means cork taint, a vinegar smell means the wine has oxidised too far, and a pushed orange colour with a flat taste means it is past its time. A deposit at the bottom means none of those things.
The confusion exists because most of us grew up on filtered and stabilised wine that stays perfectly clear in any conditions. Those wines produce no sediment because they were treated to remove every solid particle. That is not necessarily worse, it is simply one way of making wine, and it has quietly trained people to read cloudiness as spoilage.
You can check the wine itself by smelling and tasting it. If the nose is clean and the flavour is what you expected, the sediment is doing no harm.
Handling a bottle with sediment
First rule: do not shake it. If you know a bottle has a few years on it, stand it upright for at least 24 hours before opening so the sediment settles and compacts at the bottom. If it has been lying down in storage, which is where it should have been to keep the cork damp, stand it up the day before.
The classic method then is decanting. Pour the wine slowly into a decanter with a light source behind the neck of the bottle. A candle is traditional and a phone screen works just as well. The moment you see the sediment reaching the neck, stop pouring. The small amount left in the bottle is the price of having the rest perfectly clean.
No decanter is needed, incidentally: any glass jug does the job. What matters is the slowness of the movement and keeping your eye on the neck rather than on the jug.
One thing worth knowing for old bottles: decanting an old wine also exposes it to air, and a very old wine can fade within minutes of being opened. A Barolo of 10 years opens remarkably after 30 to 40 minutes in a decanter; something considerably older should be poured off the sediment and drunk fairly promptly instead of being left to breathe.
Domande frequenti
Is sediment harmful if I swallow some?
No. It is made of natural grape substances, tartrates and tannins. The texture can be unpleasant, and it is not toxic or harmful in any way.
Do all red wines produce sediment?
No. Filtered and stabilised wines, which is most commercial wine, produce no visible deposit. It is most common in bottles with years behind them, in lightly filtered artisanal wines, and in natural and biodynamic bottlings.
Can I keep a bottle with sediment for a few more years?
Yes, given proper conditions: darkness, a steady temperature around 14 to 16 degrees, decent humidity and the bottle lying down. Sediment does not speed up deterioration. It will simply increase.
Does sediment change the taste?
Not in the glass, if you decanted properly. Drinking the wine with sediment stirred through it adds an astringent edge from the precipitated tannins. Nothing dramatic, and decanting makes the whole thing cleaner.
Can white wines have sediment?
Yes, though less often. In whites it is mostly tartrate crystals, transparent or faintly amber, sometimes called wine diamonds. They are harmless and often appear when a bottle has been kept very cold.
Should I send back a bottle with sediment in a restaurant?
No. Sediment in an aged red is expected, and a good sommelier will decant it in front of you without being asked. Send a bottle back for cork taint or oxidation, not for a deposit.