Those are all great questions, let me see which order I’ll tackle them in. Firstly, we discuss corks for the most part on the pages of WineMaker Magazine not because they’re the only closure choice out there available to winemakers but because they’re simply the easiest closure for home winemakers, i.e. winemakers that typically bottle only a few cases of wine at a time, to use. You see, applying a metal screw cap (sometimes called a “twist-off” in the trade) requires a special machine as part of the bottling process that just isn’t available to the majority of folks making wine at home. Sure, if you know someone well in Wine Country and they have a small bottling line with a screw cap applicator machine in-line, you might be able to convince them to allow you to bottle your barrels, but it’s not a machine available at most homebrewing and home winemaking supply stores. If you make wine on a carboy-scale (5–10 gallons/19–38 L) there’s no way that it’s practical for you to put your wine through a winery bottling line — that volume wouldn’t get anywhere near to filling up the pipes leading to the filler bowl. Which is why, for small volumes we still talk largely about corks and not screwcaps as the bottling solution for our readers. Once a seal on a twist-off is broken, it’s not really completely 100% resealable. Small amounts of oxygen and spoilage microbes may enter your wine. For long-term wine storage, I would prefer to use a traditional cork than try to use, over and over again, a twist-off bottle. A couple of handfuls of good-quality corks and an analog no-electricity-needed hand-corker machine (which can be rented from your friendly neighborhood home winemaking store) are all you need.
Which is not to say that corks are without their problems. As I’m sure you know, corks can be a source of “cork taint” (trichloroanisole) contamination, which smells swampy and in high levels can ruin a bottle of wine. Which is one of the reasons more and more winemakers in the commercial space (as I have with the Garnet Vineyards wines I make) are bottled with a twist-off closure.
It’s not just your imagination that you’re seeing more twist-offs on the market shelves. I recently read an article that stated 38% of US wineries are using screw caps for some or all of their wine, “up from a mere 4% in 2004.” Especially in whites, pink wines, and Pinot Noir (which may have more to do with perceived consumer acceptance and conservative marketing than actual wine aging dynamics) screwcaps are to be found everywhere and in every price point. Flavor and aging-dynamic wise, I like how a screwcap is predictable and consistent for wines. Corks are nothing but a plug of tree bark, with all the good (“traditional” visuals and marketing signaling), bad (uneven expansion into bottle necks which can mean premature oxidation and bottle variation), and ugly (possible TCA). Far from signaling cheapness, quality twist offs actually are right up there in cost with corks. Twist offs have other benefits besides being TCA-free. They can be fully recycled along with your glass wine bottle, they don’t require a corkscrew (what other consumer product that you know of requires a specialized tool to access it?) and they can be easily sealed up again. I believe in quality and convenience, and evidently so do a lot of other winemakers, which is why I like to use twist-offs for Garnet Vineyards. I worked for Bonny Doon Vineyards for about five years during the time when that innovative winery was switching over from corks to twist-offs so I gained a confidence with this closure. However, best-quality corks are still simply the easiest closure for smallest-scale winemakers to find, buy and utilize.