A few years back, I figured that half-bottles of wine would come on strong. Not the case, despite my reasoning: About half of U.S. adults are single and (one would hope) unlikely to polish off an entire 750-ml bottle in an evening. And in “mixed marriages” — he likes red wine, she prefers white — the same result unfolds if they go the “to each his/her own wine” route on a given night.

Almost inevitably and no matter what measures are taken, the rest of the bottle is not nearly as fresh and tasty whether it’s a day later or three. And so wine has been wasted, an egregious sin for many of us. (Oddly, I have had many syrahs that actually were better on the second night, the proverbial exception that proves the rule.)

As soon as a cork is popped or a cap is unscrewed, oxygen can start degrading a wine. Admittedly, some young, tightly wound wines can “open up” with decanting and aerating. Otherwise, the effects tend to be negative. That’s why old wines generally should not be decanted, because they already are seeing more life-sucking air than they have in decades.

Restaurateurs have known about this effect for decades, which is why they often charge the same amount for a glass that they paid for the entire bottle; the rest eventually might have to be tossed. Anything served even a day later is likely to be inferior. When ordering by the glass, I always add “if the bottle was opened today,” and opt for another wine if it wasn’t.

The exception is if the establishment has a wine-preservation system. These glass-encased setups, pioneered locally at Broder’s Pasta Bar and at Terzo, use argon and/or nitrogen gas systems to replace the oxygen in the bottle and can keep wines fresh for two to four weeks. They also keep the bottles at a consistent optimum temperature, i.e., cooler than room temp. Other restaurants — including In Bloom, Gianni’s, Ngon, the Cooper and Red Rabbit — have added these machines.

Alas, these machines are too spendy to have at home, but we do have some options:

• Buy stoppers, the rubber ones for regular wines and the specialized ones for bubbles (which have the added benefit of making a cool “let’s drink” sound when removed). The “Wine Saver” devices made by Vacu Vin work well, too. I haven’t had much success with the sprays that some companies make.

• Local wine expert Paul Daggett has always said that sparkling wines don’t lose their fizz or freshness in the refrigerator, even without a topper. His explanation was too technical for someone like me, but I’ve tried it and it has worked.

• For those with wine cellars, the Coravin can be a good option despite costing a few hundred dollars. The thin needle pierces the cork and allows a pour of any size, and then the cork reseals, meaning virtually no oxygen gets in. More and more restaurants, including the top steakhouses, are using these with high-end wines.

• Refrigerate reds that have been opened and resealed, especially lighter ones such as pinot noirs, barberas and cabernet francs. The cooler temps slow any spoilage the same way they do with meats, fruits and veggies. Wine is food, after all.

• Half-bottles do have their usefulness, it turns out. (Actually, my original theory works, but now the ever-more-popular cans are filling the bill in that realm.) Pour wine into a screw-cap half bottle or even an empty water or soda pop bottle, which will have far less air than the 750-ml.

Here’s what not to do: Use fading or faded wine for cooking. You wouldn’t use wilted herbs or other ingredients past their prime, right? (Remember, wine is food.)

What you can do, if you want to go to the trouble, is make vinegar — especially since your wine is en route to that status already.

Begin with the “starter,” pouring some red-wine vinegar or white-wine vinegar into larger, labeled, sealed containers placed in a pantry or cellar. Pour unused wines into the appropriate container, cleaning and saving the wine bottles for the vinegar to come.

Taste them every week or so, and add a tiny bit of sweetener if they get too sour or bitter. If the red mixture develops a rather disgusting-looking blob, that’s actually a good thing; don’t ask me why because, well, science.

When you have enough to bottle, pour some liquid (but not the blob) into a big pot and bring to a boil, then quickly remove it from the heat and strain through a cheesecloth before pouring back into the original wine bottle.

The result is the rare re-corked liquid that is not susceptible to spoilage.

 

Bill Ward writes at decant-this.com. Follow him on Twitter: @billward4.