Before bottling, sugar, yeast, yeast nutrients and adjuvants are added to the wine.

Sugar

20 - 25 g/l in order to produce around 5 - 6 bar pressure. The higher the alcohol level, the more you add.

Yeast

The yeast must withstand high alcohol levels, high pressure, low nutrient status, high acidity, high SO₂ (sulphur dioxide) and still ferment to dryness. It should not produce off-flavours, such as H₂S (hydrogen sulphide), VA (volatile acidity), or ethyl acetate
The yeast should autolyse rapidly but also agglomerate and flocculate. A common inoculation is 15 g/hl of yeast EC1118 (S. cerevisiae var bayanus), rehydrated in ten times its own weight of water (37ºC), then double volume with wine every half hour.

The target yeast cell count is 2 - 4 x 10⁶ viable cells/ml, and this should be confirmed before innoculation. Higher yeast counts can cause competition for nutrients which causes metabolic deficiencies leading to hydrogen sulphide. Yeast must be in very good health (high reserves & sterols) and be acclimatised to alcohol and low temperature.

Yeast nutrients

Up to 200 mg/l diammonium phosphate (DAP), plus 0.5 mg/l Biotin

Adjuvants

These help the agglomeration and flocculation of yeast and so help riddling. E.g;

• 4 g/hl tannin + 1 - 2 g/hl gelatin
• 2.5 - 5 g/hl bentonite
• 1 - 5 g/hl alginate

It can be difficult to determine how much of the adjuvants to add, but excessive use will make riddling difficult.

It is important to keep the mixture of wine, sugar, yeast, yeast nutrients and adjuvants agitated during bottling in order to keep in suspension. Second-hand bottles should not be used due to the risk of stress fractures. Bidules are a good idea before crown caps as they aid in disgorging; often combined bidules/crown caps used. Stainless steel crown caps are rust free but very springy.

The second fermentation (Prise de Mousse) temperature has a large effect on quality, especially bubble size. The optimum is 12 - 14ºC.