"I assume this is sediment. What is sediment exactly and why does it happen?” —Tom W. (Atlanta, Georgia)

Tom, that’s it alright. Sediment is made up of color and tannin molecules that have polymerized (linked together) and gotten heavy enough to fall out of solution. Typically, this only happens after the wine is ten or more years old. And it’s most likely to occur with deeply colored wines that have a lot of tannin to begin with—wines from varieties such as cabernet sauvignon, merlot, petit verdot and the Port varieties. Sediment can get pretty sticky (as in your photo) and some of it will cling to the sides of the bottle. Lastly, sediment is harmless, so if you swallow some, don’t worry.

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