Put simply, when making still wines the Carbon Dioxide produced in the fermenting must is allowed to escape - for sparkling wines it is trapped. That's what the fizz in the bottle is, although methods and refinements vary considerably. By far the finest and best-known method is that used in Champagne, and known world wide as the 'methodé champenoise'.This involves a secondary fermentation in the bottle in which it is sold. It was invented in the late 17th century by the monk, Dom Pérignon, and has been copied with considerable success throughout the world. The name Champagne is however protected by law and the term 'methodé champenoise' cannot be used for wines made outside the Champagne region.
A still base wine is made in the normal way and carefully blended with other reserve wines until it attains the specific 'House' style. It then rests on its lees to extract flavour and is stabilised. The next stage involves the addition of a sugar and yeast mixture prior to bottling in special strong bottles with crown corks. The addition of the sugar and yeast starts a second fermentation in the bottle with the resultant bubbles trapped inside.
The bottles are then stored in almost vertical racks, known as 'pupitres' and traditionally every bottle was twisted and turned by hand to encourage the yeast deposit down to the neck of the bottle. This process is known as 'remuage' or riddling and was extremely labour intensive. Although still practised today, many 'Houses' have adopted the mechanical 'gyropalette' to perform the task.
Once the deposit has moved to the neck of the bottle, it is then frozen in a brine solution, upended and 'disgorged' as a solid lump of ice from the pressure of the gas. The bottles are then topped up with a wine and sugar mixture known as the 'dosage', and then corked with the traditional champagne cork and wire tie.
Other less refined methods are used in the more commercial sector with the secondary fermentation taking place in a tank, prior to bottling. At the bottom of the scale is the injection method where carbonic gas is simply injected into the base wine, as you would do with a fizzy soft drink. Not to be recommended.
