This section is from the book "Monograph on Flavoring Extracts With Essences, Syrups, and Colorings", by Joseph Harrop . Also available from Amazon: Monograph On Flavoring Extracts With Essences, Syrups And Colorings.
"From reliable fruit juices fruit syrups may be made for immediate use by mixing the contents of a bottle with three or four times its bulk of dense simple syrup or rock candy syrup. Beyond this point of dilution the dealer may go to such an extent as he chooses, but the smaller cost is offset by the disappointment of the consumer of the beverage, and we urge that a full, good flavor should not be sacrificed.
"Concentrated syrups from fruit juices will best suit those who do a small business; for this purpose, take the contents of a bottle of the juice, and weighing it, add one and three-fourths the weight of sugar and cause it to dissolve, using but little heat. When used for the soda fountain, add the same bulk of simple syrup or rock candy syrup, and to the mixture one-fourth the bulk of boiled and filtered water."
The fruit syrup formulas which follow are, for the most part, the result of long experience, and may be relied on as correct in every particular. The third name referred to in the preface being authority for most of them.
* See page iv., Pub's Dept.
To make one (1) gallon of raspberry, strawberry or blackberry syrup -
Take of the Fresh Fruit...........
Water, a sufficient quantity.
Express the juice and strain, then add Water until it measures four (4) pints; dissolve the Sugar in this by the aid of heat, raise it to the boiling point, and strain. If it is to be kept until the following season, it should be poured, while hot, into dry bottles, filled to the neck, and securely corked and sealed.
These syrups contain a small quantity of alcohol, and keep well in sealed bottles, but exposed to the air, they soon undergo acetous fermentation.