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Dear Dr. Vinny,

I would be pleased if you could shed some light on the chemical makeup of the substance that forms in between the cork and a wine bottle’s neck that prevents the use of the various types of corkscrews that are normally used to extract corks.

I understand that the neck of the bottle can be tapered and does not assist the cork to be extracted, but sometimes the cork is old and deteriorating but is still held in the neck of the bottle by the stickiness between the cork and the bottle’s neck.

I also understand that tartrate crystals are formed on the bottom of the cork, but are they also formed in between the bottleneck and the cork? Or is there a different chemical action taking place, which adheres to one or other of the surfaces to cause the sticking problem?

—Peter W., Kidderminster, England

Dear Peter,

I’m also a fellow wine lover who has been stumped on occasion by particularly stubborn corks. Keep in mind that there is no chemical or substance or sticky matter applied to keep a cork in place in the neck of a bottle. Rather, it’s the unique qualities of cork itself that make it such an efficient stopper. Cork has a unique honeycomb cell structure filled with air, and it’s extremely elastic. Cork can be compressed—as it is in the neck of a wine bottle—and then, after it’s removed, it can expand back to its original volume. If you’ve ever tried to put a cork back in a bottle after removing it and found that it can’t fit, you’ve seen that it can expand very quickly.

Something tells me that if you’re having trouble opening bottles of wine, then you might need a better corkscrew. There are many models (and price points) out there, but for about $10 you can get what’s called a waiter’s corkscrew. It can give you some added leverage, and here’s a video that will show you how best to use it.

That said, I’m familiar with the phenomenon you’re describing in old, damaged wines. When I pull the corkscrew, the core of the cork comes out, leaving a cylinder of cork stuck to the bottle that won’t come out at all. I’m not sure why this happens, but my suspicion is that the bottle was heated at some point, thus pushing the wine up between the glass and the cork, and then it cooled, leaving the wine to dry out and form a bond between the cork and the glass.

As far as tartrate crystals—those harmless little white chunks that sometimes cling to the bottom of a cork—are concerned, I’ve never seen them form between a cork and the bottle.

—Dr. Vinny

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