What are synthetic wine corks made of?

Ask Dr Vinny

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.

Dear Dr. Vinny,

What are synthetic wine corks made of?

—Adrian, United Kingdom

Dear Adrian,

The two main types of synthetic corks are made from either petrochemical-based plastics or plant-based plastics.

The petrochemical-based plastics are made from low-density polyethylene, a pliable type of plastic. Plastic pellets are melted down, and then turned into a foam consistency so they’ll mimic natural cork’s spongy texture, typically then covered with a smooth outer skin.

The plant-based plastic corks are similar in production, except that they are made from biopolyethylene, a type of renewable polyethylene that’s made from ethanol derived from the dehydration process of raw materials like sugarcane and sugar beets.

The plant-based synthetics are increasing in popularity, since they have a low carbon footprint and are renewable. Bioplastics like these are also commonly used to make water and soda bottles.

Why do some wineries choose synthetics over traditional natural corks, screwcaps or composites? Synthetic corks are cheap: They cost about a dime to 15 cents each, about the same as a composite cork; screwcaps can cost up to 25 cents, and good-quality natural corks can cost anywhere from 75 cents to $2. Some folks opt for synthetic corks to eliminate the risk of "cork taint," or the potential for irregularities that arises from using a natural product like cork.

I don’t mind synthetic corks, but they can be really hard to get out of the bottle—they can be so stiff sometimes that I’ve actually broken a corkscrew on a couple of them. I’ve also heard anecdotal reports that wine aged for a long time (years) under synthetic cork can take on some off odors or flavors that may be linked to the plastic.

—Dr. Vinny

Closures Ask Dr. Vinny

More In Dr. Vinny

What does it mean when a tasting note refers to the “midpalate”? How do you experience it?

Wine Spectator's expert Dr. Vinny explains how—and when—the midpalate is experienced.

Nov 23, 2020

Is my home wine cellar supposed to smell like wine?

Wine Spectator's expert Dr. Vinny explains possible sources of a wine aroma in a bottle …

Nov 16, 2020

What do you call white wines that have a citrusy, fizzy sensation?

Wine Spectator's expert Dr. Vinny explains the difference between acidity and effervescence.

Nov 13, 2020

Should I be concerned about wine freezing in my car if it’s below freezing outside?

Wine Spectator's expert Dr. Vinny answers questions about freezing wine.

Nov 11, 2020

Do you recommend any wine clubs? Are they good holiday gifts for wine lovers?

Wine Spectator's expert Dr. Vinny offers tips for choosing a wine club.

Nov 9, 2020

Could smoke taint in wine be removed by reverse osmosis?

Wine Spectator's expert Dr. Vinny explains how reverse osmosis is used as a tool for …

Nov 6, 2020