Like many sparkling wines, champagne is produced by the traditional or classic method, which is characterized by a second fermentation in the very same bottle in which the wine eventually comes to be sold. Although the traditional method is usually thought of as the best method for producing sparkling wine, it is the only method that does not require expensive, large scale equipment, and hence the only method that is available to the small scale producer.
The grapes that go into making champagne require both high acidity and phenolic ripeness, a combination that is much easier to achieve in the cool Champagne region than in warmer climates. So as to preserve acidity, grapes are harvested early at a low must weight. This comes at the expense of sugar content, which is made up for by the subsequent addition of sugar in the form of liqueur de tirage and liqueur de dosage and also, in some cases, by initial chaptalization (see later). In black grapes it also comes at the expense of colour, which for champagne is in fact a benefit.
The vineyards are harvested by hand and whole bunches are cut. This ensures not only that individual grapes are left undamaged but also that the juice can run off quickly along the stalks, which act as drainage channels in the press. The grapes are pressed without delay, traditionally in a basket or Coquard press although other types of press, notably the Vaslin horizontal press and the more delicate Wilmes horizontal press, are also used. Gentle pressure is applied so as to minimize the extraction of undesirable colour and tannin. By law, only 102 litres of must can be extracted from every 160 kilos of grapes. The first 80 litres to emerge are the cuvée. The cuvée is of the finest quality as it is highest in acidity and sugar and lowest in phenolics. The remaining 22 litres are the taille which may or may not be excluded, and anything beyond 102 litres is the vin de rebèche which cannot be used for champagne. After pressing, the must is clarified although some solids need to be retained to facilitate the second fermentation. The must may also be chaptalized at this stage.
Next the must is fermented to a still wine, normally in stainless steel vats although some producers such as Bollinger and Krug use (old) oak casks. Too cool a fermentation temperature encourages the formation of undesirable amylic aromas, which may mask some of the much more subtle and complex aromas of the finished champagne. Most champagne houses encourage malolactic fermentation although some, most notably Lanson, prefer to avoid it.
Grapes from different plots and parcels are vinified separately. In the spring following the harvest these vins clairs are blended along with varying proportions of reserve wine from older vintages. This process of blending or assemblage aims not only at balance and complexity but also at producing a consistent house style. As several of the numerous parameters of the savant mélange are highly vintage dependent, there can be no fixed recipe for the house style and every release is the product of the fine and expert judgement of a master blender.
The blended still wine, though full of promise, is not particularly pleasant to drink. It is bottled together with the liqueur de tirage, a mixture of wine, sugar, and yeast. The purpose of the liqueur de tirage is to induce a second, slower fermentation or prise de mousse in the bottle. Around 24 grams of sugar per litre are required to add around 1.2% of alcohol. This brings total alcohol to around 12% and also yields sufficient carbon dioxide for a bottle pressure of around 5-6 atmospheres – 5-6 times atmospheric pressure at sea level or the same pressure as in the tire of a double-decker bus!
The bottles are sealed with a crown cap and laid horizontally sur lattes in a cool cellar. The prise de mousse takes place over a period of perhaps 4-8 weeks after which the wine is left to mature, in some cases for several years, on the dead yeast or lees. During this long period, the gradual breakdown of yeast cells releases mannoproteins, polysaccharides, and anti-oxidative enzymes into the wine. This yeast autolysis results in a fuller body with a more unctuous mouthfeel; reduced bitterness and astringency; complex aromas of biscuit, bread dough, nuttiness, and acacia; and improved ageing potential. By law, non-vintage wines must sit on the lees for a minimum period of 15 months and vintage wines for a minimum period of 36 months. Many producers largely exceed these minimum requirements.
Compared to blending and ageing on the lees, the remaining steps in the method of production of champagne add relatively little to overall quality. The bottles are first agitated so as to loosen and consolidate the sediment, a process called poignettage. The yeast deposit is then gradually moved into the neck of the bottle. Traditionally, this is carried out over 8-10 weeks on a pupitre, a wooden frame with 60 holes bored at an angle of 45 degrees on which bottles can be manually turned from horizontal to vertical. Nowadays, this process of riddling or remuage is far more likely to be carried out on a much larger scale and in a much shorter time by a mechanized gyropalette. Once the bottle is vertical, it is left in this position (sur pointes) for a further period of maturation.
Next, the crown cap and lees are removed. This process of disgorgement used to be carried out by hand or à la volée. Today it is usually carried out in an automated process that involves freezing the material in the neck of the bottle and ejecting this ice plug under the pressure of the wine. The liqueur d’expédition or dosage is then added. This consists of a mixture of the base wine and varying amounts of sugar that serves both to balance acidity and to determine the final style of the wine. By far the most common style is brut with added sugar of 6-15g/L. Other fairly common styles are extra brut with 0-6g/L and demi-sec with 35-50g/L.
A composite or agglomerated cork with whole cork attached to the base is inserted and held in place by a capsule and wire cage (muselet). But the wine is not yet ready to drink, and a further rest period is required for the dosage to marry with the wine. During this period, a number of chemical reactions between sugar in the dosage and amino acids in the wine yield additional aromas of dried fruit, toast, and vanilla that add to the overall complexity of the wine. Some authorities have argued that zero dosage wines (bone dry wines with no added sugar) are unable to benefit from this so-called Maillard reaction, as a result of which they have a relatively limited ageing potential.
To produce the smallest and largest bottle sizes (beyond jeroboam i.e. double magnum or 3 litres), the wine is disgorged into a pressure tank, the dosage is added to the tank, and the wine is rebottled – a process called transversage. No doubt there is something lost in this process, even though it may not be very much. Bottle sizes beyond jeroboam are rehoboam (4.5 litres), methusalem (6 litres), salmanazar (9 litres), balthazar (12 litres), and nebuchadnezzar (15 litres), and it is not entirely clear why they have been or should be named after biblical characters.
The method of production described above may be slightly adapted for different styles of champagne. Vintage champagne is not made every year but only in very good to exceptional years. The wines that go into the assemblage must all be from the same declared vintage and the minimum period for ageing on the lees is 36 months. Compared to non-vintage champagne, vintage champagne is richer and fuller and more apt to improve with bottle age. A producer may also indulge in a cuvée de prestige, which is normally a vintage champagne made from premium grapes and/or aged for an even longer period. Pink champagne, which accounts for about 7% of total production, is made by adding a small amount of still red wine prior to first fermentation. Champagne that is sold as ‘recently disgorged’ or similar is champagne that has benefited from prolonged yeast ageing and that has been released for sale soon after disgorgement. If consumed soon after release, this champagne can taste especially fresh, fruity, and complex.