What's with the sediment in my wine?

A lot of people probably have questions about the sediment at the bottom of a bottle of wine.  What is it exactly?  Is it good?  Is it bad?  Should I drink it?

Well, these questions are all complicated.  In short, sediment in wine comes from many sources.

Sediment can consist of debris from the winemaking process, lees (dead yeast cells), and tartrate crystals, or, usually, some combination of the above.

Wine is naturally a hazy substance.  The yeast which has created the alcohol is suspended in the wine, as are tiny particles of grape skin, pips, seeds, etc.  Many wines are filtered or fined to remove sediment, although, unfiltered and unfined wines are becoming more popular for several reasons (biodynmic and vegan winemaking, health concerns, and a healthy respect for more natural wines among them).  Moreover, the process of filtering out or, especially, fining out "undesireable" sediment can also remove things which positively affect the way the wine develops with age.  This is why white wines, and red wines meant to be drunk young, are more often filtered or fined.

Moreover, as wine ages, tartrates crystalize in the wine, particularly if the wine is stored in or transported in, cool temperatures.  These are perfectly harmless, but not temperature stable, substances found in all wines.  As the wines chill, they crystalize and fall to the bottom of the wine.  Barrel aging wine allows many tartrates to crystallize before the wine is bottled, but wines which are bottled young have more tartrates to crystalize.  Many winemakers "cold stabilize" their wines, chilling them and removing tartrate crystals before bottling the wine.  Like filtering and fining, the problem is that you can also filter out many things that contribute to desireable changes during bottle aging.  So, again, this is much more common in wines meant to be consumed in their early years.

As far as if sediment is good or bad, the answer is really neither, but leans toward good, particularly n older wines.  Sediment is perfectly harmless, and the compounds in the sediment, particularly grape remnants and lees, can contribute great flavors to wine as they age.  As far as if you should drink sediment, the general feeling seems to be no.  This is the main reason to decant wine (as opposed to aerating it, which also involves putting it in a decanter).  By carefully pouring the wine into the decanter, and by again, carefully pouring from the decanter to the glass, you can avoid most, if not all, of the sediment.  If a little sneaks into the glass, though, it's not the end of the world.  I think for the most part, the aversion to sediment is more of a personal taste, and based primarily on texture, especially since sediment settles at the bottom of the bottle and glass, so the last sip of the last glass poured would have quite an interesting texture to it.