No one questions that screw top wine closures are handy, particularly when you're at a picnic and forgot to pack a corkscrew. But many wine drinkers do not take them seriously, and I have heard sommeliers (who should know better) claim that wines in screw top bottles are not serious or capable of aging. Stuart Blackwell, senior winemaker at St. Hallett's Barossa winery, takes exception with this view and is very happy that all of his wines--even the highly regarded Old Block Shiraz--are now protected by screw tops.
Blackwell pointed out that 24 percent of the bottles of his excellent 1991 Old Block Shiraz were tainted by bad corks--a very distressing situation for the winemaker as well as the consumer. Most wine drinkers recognize the damp cardboard smell and off flavors of a badly corked wine, but the signs in many corked wines are not that obvious. Some have a vague woody quality; others merely smell and taste stunted, failing to show their expected aromas and flavors. Reputable merchants and wineries will, of course, replace corked bottles, and the problem was so bad in 1991 that Blackwell had to hold back about a third of his production back in order to provide replacement bottles to his customers. He's still searching for bottles, in fact, and buys back bottles whenever he can find them at auction.
The advantage of the screw top closure, according to Blackwell, is not just to protect the wine from bad cork smells and flavors but to allow the winemaker more control over the finished product. Good wine always involves an interaction with a small amount of oxygen that is in the space between the wine and the cork or fights it way through the cork, Blackwell said. (The matter of air getting through the cork is a controversial matter, by the way.) In a screw top, no air gets through so Blackwell adds more oxygen to each bottle, and the result is a wine that shows better when it's young but is still capable of aging. He's been using screw tops long enough to be confident of the long-term as well as the short-term results.