Designation for that part of the empty space in a fermentation tank which serves as a reserve. The tank must not be completely filled as the grape must heats up during fermentation and its volume may increase considerably. The rising space must make up 5 to 10% of the volume of the vat, or even about 25% in the case of closed maceration. See also under fermentation attachment (devices made of glass which are placed on the closure hole of the fermentation tank).
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