How do you soften a hard cork?

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Dear Dr. Vinny,
How do you soften a hard cork?
—Denis, Parker, Colo.
Dear Denis,
If you’re hoping to moisten a cork so it’s easier to put back into an already-opened bottle, keep in mind that putting the cork back in is just a temporary stopgap. It’s not like you can put the cork back in and the wine will continue to age: Once you open a wine bottle, that cork has left the barn, so to speak, and the wine will fade over the next several days as it reacts with oxygen.
But if you are just looking for a temporary solution, it’s usually much easier to put the cork back in if you flip it, so that the wine-stained end is now on the outside. That’ll do just fine for a day or two.
If you’re trying to revitalize a cork that has already dried out, there’s not much you can do to re-moisten it, but you can help limit further drying out by applying some food-grade mineral oil.
If you’re going to be doing crafts with leftover corks and need to soften them to make them easier to cut, I’ve seen both steaming them as if they were vegetables or boiling them for a few minutes. Of course, wait until they’re cool enough to handle.
On the other hand, if you’re asking because you’re a budding winemaker and not sure about your first time corking, check with your cork supplier for their recommendation. Corks can be both sterilized and softened by either steaming them, or submerging them in a solution of sodium metabisulfite and cold water.
—Dr. Vinny