Champagne corks are built from several sections and are referred to as agglomerated corks. The mushroom shape that occurs in the transition is a result of the bottom section, which is in contact with the wine, being composed of two stacked discs of pristine cork, cemented to the upper portion which is a conglomerate of ground cork and glue. Prior to insertion, a sparkling wine cork is almost 50% larger than the opening of the bottle. Originally they start as a cylinder and are compressed prior to insertion into the bottle.
Pouring sparkling wine while tilting the glass at an angle and gently sliding in the liquid along the side will preserve the most bubbles, as opposed to pouring directly down to create a head of “mousse”, according to the study On the Losses of Dissolved CO2 during Champagne serving. Colder bottle temperatures also result in reduced loss of gas. The industry is also developing Champagne glasses designed specifically to reduce the amount of gas lost.
Champagne is primarily a product of vast blending – of different grape varieties, different vintages and different vineyards – with a typical non-vintage blend being composed of grapes from up to 80 different vineyards. However for their prestige cuvee (such as Moët et Chandon’s Dom Pérignon or Louis Roederer’s Cristal) Champagne producers will often limit the grape sources to only Grand cru (and sometimes Premier crus) vineyards. While single vineyard Champagnes are rare, they do exist, such as Krug’s Clos du Mesnil coming from the Grand cru vineyard located near Le Mesnil-sur-Oger. Grower Champagnes, the product of a single producer and vineyard owner, located in Grand cru villages will often label their wines “100% Grand cru” if their wines qualify for the designation.