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Fortification Point


Initial must °Brix
Desired alcohol (%v/v)
Spirit alcohol (%v/v)
Volume of wine
Desired °Brix in finished wine
Alcohol produced by fermentation (%v/v)
Fortify when hydrometer reads (°Brix)
Volume of spirit to add


Details:  This calculator calculates the point of fortification for making fortified wines with residual grape-sugar (e.g. Port).  It accounts for both the obscuration of sugar, by the alcohol produced during fermentation, and the dilution of the residual sugar, during fortification.



This calculator finds the fortification point for making fortified wines which contain residual grape-sugar, such as Port.  The formulae are derrived from the following:

Brix_in_fortified_wine = Brix_must / ( 1 + (1 / R) )

R = ( Alcohol_spirit - Alcohol_target ) / ( Alcohol_target - Alcohol_must)

Alcohol_in_fortified_wine = ( Brix_initial - Brix_current ) / 1.8

True-Brix = ( 97 * Brix_initial + 1200 * Brix_Current ) / 1297

These are combined and used to derive:

Fortification_Point = - ( 291 * Brix_initial * Alcohol_target + ( 3891 * Brix_final - 291 * Brix_initial ) * Alcohol_spirit - 2000 * Brix_final * Brix_initial ) / ( 3600 * Alcohol_target - 3600 * Alcohol_spirit + 2000 * Brix_final )



VinoCalc by Jonathan Musther  -  jon@musther.net