Under Pressure: The Craft and Chemistry of Sparkling Wine. How do the world’s finest bubbles get into your glass? We explore the science, regions, and traditions of sparkling wine.

Welcome to the Wine Lab! I'm Andrea Bottasato, your host, and today we're diving into one of the most celebratory styles of wine in the world - sparkling wine. From centuries-old sellers in Champagne to sunlit vineyards in Italy, from the crisp elegance of brute nature to the playful charm of pétillon naturelle, sparkling wine has a story as lively as its bubbles. We'll explore how it's made, the science of secondary fermentation, the regions and methods that define it, and even a few fascinating historical twists along the way. So pour yourself a glass, still or sparkling, and let's get started! There's something almost hypnotic about watching a stream of tiny bubbles rise through a glass of sparkling wine. It feels alive, joyful, celebratory and timeless. But behind that sparkle lies centuries of human ingenuity, scientific discovery, and more than a few happy accidents. Let's start with a bit of history, because sparkling wine wasn't always the refined, intentional drink we know today. In fact, in 17th century France, winemakers in Champagne were frustrated. They produced still wines, but during the cold winters, fermentation would stop early. When spring warmth returned, fermentation restarted in the bottle, unexpectedly creating bubbles. The glass bottles of that time often couldn't withstand the pressure and would explode in sellers, earning sparkling wine the nickname the Devil's Wine. Yet, slowly, this defect transformed into a luxury. By the late 1600s and early 1700s, sparkling wine became fashionable in royal courts across Europe, and winemakers began to refine the process. One legendary figure in this story is Barb Nicole Ponsardin, better known as La Veuve Cliqueau. Widowed at just 27, she took over her husband's struggling Champagne house and turned it into a global icon. Among her many contributions, she invented the riddling rack in the early 1800s, a method of gradually tilting and turning bottles to collect yeast sediment in the neck, making it easier to remove and leaving the wine beautifully clear. Her innovation remains central to traditional sparkling wine production today. Now on to how sparkling wines are made, because there is more than one way to put bubbles in a bottle. All sparkling wines begin like still wines. Grapes are harvested, pressed and fermented into a base wine, but it's the second fermentation that creates carbonation. The most famous technique is the traditional method, or method traditionnel, perfected in champagne. Winemakers add a mixture of sugar and yeast, called liqueur de tirage, to the base wine before sealing it in thick glass bottles with a crown cap. As yeast consumes the sugar, it releases carbon dioxide which has nowhere to escape, dissolving into the wine and creating fine, persistent bubbles. These bottles then age on their leaves for months or even years. This aging imparts flavors of brioche, toast and nuttiness, a hallmark of high quality sparkling wines. Once aging is complete, riddling, thanks to Lavov-Clicot, concentrates the sediment in the bottle's neck. It's then frozen and quickly expelled in a process called disgorgement, after which a dosage, which is a mix of wine and sugar, is added to adjust sweetness before corking and wire caging the final bottle. And that dosage plays a big role in determining sweetness levels. Sparkling wines are classified by their residual sugar content, and the labelling can be a little counter-intuitive. Brute nature, or zero dosage, has less than three grams of sugar per liter and no added sweetness. Crisp, dry and razor sharp. Extra-brute is similarly dry, followed by brute, the most popular category worldwide, balancing freshness with just a hint of softness. Move up the scale and you get extra dry, which confusingly is actually a touch sweeter than brute. Then sec, demisec, and finally do, or sweet, which can be lusciously sweet and dessert-like. This sugar not only impacts taste, but also texture, balancing acidity and shaping how the wine feels on the palate. Going back to production methods, across the Alps, in Italy, a different style emerged. The Charmat method, also called the Tank method. Here, the second fermentation happens not in individual bottles, but in large, pressurized tanks. The result is fresher, fruitier wines, think classic Prosecco, with aromas of pear, apple, and white flowers, rather than the toasty complexity of champagne. This method is faster and less labor-intensive, making sparkling wine more accessible, while highlighting primary grape aromas. Spain's Cava mostly uses the traditional method, delivering incredible value for wines with citrusy brightness and delicate complexity. And modern winemakers in California, Australia, and South Africa have adopted and adapted these approaches, producing world-class sparkling wines that reflect their local terroir and grape varieties. There's also the ancestral method, or pétillon naturel, which predates champagne. With this technique, fermentation starts in a tank or a barrel and is finished in the bottle without disgorgement. The result is a rustic, lightly cloudy, naturally sparkling wine with playful, less predictable bubbles, a style now popular with natural wine enthusiasts. But not all sparkling wine is crafted through secondary fermentation. Some producers simply inject carbon dioxide, much like soda, into still wine. This is the quickest, cheapest way to add fizz, producing coarse bubbles that dissipate quickly. While not considered fine sparkling wine, this method fills a niche for inexpensive, easy-drinking bubbly. From a scientific perspective, making sparkling wine is a masterclass in microbiology and chemistry. Yeast strains must withstand high alcohol levels and the pressure of a sealed bottle. The sugar-to-yeast ratio must be carefully controlled to achieve the desired carbonation level. Too much and bottles can burst. Too little and the wine won't sparkle. During Lee's aging, enzymes released from dead yeast cells transform the wine's texture and flavor, softening acidity and adding creaminess. Even the bottle itself is engineered to hold pressures up to six atmospheres. That's nearly the same as a double-decker bus tire. Ultimately sparkling wines are not just beverages, they're feats of craftsmanship and patience. Whether it's the elegance of champagne, the freshness of Prosecco or the earthy charm of a pet nut, each style reflects centuries of evolution in both technique and understanding of fermentation science. So next time you hear that satisfying pop and watch bubbles rise to the surface, remember your holding centuries of history, a dash of serendipity and the result of precise beautiful science captured in one sparkling glass. If you enjoyed this episode of the Wine Lab, I'd love to hear from you. What's your favorite style of sparkling wine? Have you ever tried making one yourself or do you have a region or wine style you'd like me to explore next? Leave a comment, send me your thoughts or suggest a topic for a future episode. Your feedback helps shape where we go next in our journey through the science and stories of wine. Cheers!