According to Caroline Krug of Champagne Krug, the discovery of the champagne we drink today was the accidental result of climate. The end of the region's warm-weather grape harvest was followed quickly by cooler weather, which slowed or stopped the fermentation process of some of the wines. When the warm weather came again in spring, the dormant yeast was reinvigorated and induced a second fermentation that gave champagne its characteristic bubbles. Dom Pierre Perignon, a Benedictine monk during the seventeenth century, experimented with methods that regulated the second fermentation: storing the wine in thicker bottles, tying the corks tightly with string, and storing the bottles upside down.
Years of refinements since Dom Perignon's time have lent consistency to the wine and a set of criteria that better defines it. In most cases, champagne blends three types of wine from three strains of grapes, usually the yield from different vineyards and sometimes, different years. Champagne makers usually blend wine made from black grapes, such pinot noir and pinot meunier, with some made with white grapes, such as chardonnay. Each grape grows in a different region, which is further subdivided into its constituent vineyards. Vineyards are known for the quality of their soil, or by which way their vines are oriented, and these characteristics deeply influence the quality of the grapes. Only wines produced in Champagne can legally be called champagne; wines produced elsewhere using the same method are called sparkling wine.
Great champagne is distinguished by the care and concentration applied to its blending and aging. Once the juices are selected, they are mixed or stored individually to undergo the primary fermentation. The second fermentation gives the wine its effervescence, after which the wine is left to age for several years.
There are several groupings that divide champagne. Non-vintage blends utilize the juice from a number of harvests and don't identify a vintage year on their labels, while vintage blends use the yield of a single year's harvest. Rose champagne adds the fermented skins from pinot noir grapes to tint the wine a light pink; cuvees de prestige, the finest champagnes, employ only the best grapes from the top vineyards. Within these categories, champagnes are further grouped according to sweetness, with demi-sec and doux being the sweetest and brut and extra brut being the dryest. The sweetness is imparted by a "dosage" of sugared wine just before the final corking, ranging in proportion from no sugar, or less than 1 percent, to more than 5 percent.
When serving champagne or sparkling wine, there are some guidelines to follow to ensure it will be at its best. It should be chilled to around 50 degrees in the refrigerator (never the freezer) or, just before serving, in a bucket of ice water. When opening the bottle, keep the cork pointed away from people or objects; undo the wire cage encasing the cork, and hold the cork firmly in one hand with the bottle in the other. Slowly turn the bottle until the cork starts to free up, bending it as it comes out of the neck.