Pearson Square

Pearson Square (Wine fortification chart)

A		D
(alcohol content of fortifying spirit)		(C-B) the difference is the fortifying spirit required
	C
	(desired alcohol content of fortified wine)
B		E
(alcohol content of existing wine)		(A-C) the difference is the part of wine to be fortified

The Pearson Square is used to determine the amount of spirit needed to fortify a wine. It is necessary to know the percentage of alcohol by volume (v/v) in the spirit to be used for fortification and also in the wine to be fortified.

For Example: Suppose the fortifying spirit has a 40% alcohol content, the wine has 15%, and you want to add enough spirit to increase the wine (e.g. port) to 20%. Subtract B (15) from C (20); the remainder D (5) are parts of spirit to be used in the mixture. Subtract C (20) from A (40); the remainder E (20) is parts of wine to be used. You will need 5 parts of spirit to 20 parts of wine to bring the mixture up to 20% alcohol by volume.

The same method can be used to calculate the alcohol content of two wines when blended.

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