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Tonic Syrup
American Tonic Extract, 2 ounces; American Fruit Acid, 2 ounces; American Soda Foam, 1 ounce; Simple Syrup, 2 quarts.
This is a soda fountain bottling formula, not a kitchen recipe: four measured components stirred together to make a bulk syrup that is later drawn by the ounce and finished with carbonated water. Three of the four ingredients are proprietary trade goods that no longer exist under those names.
- What the ingredients actually were"American" here is a supply house brand, not a description. Tonic Extract was a flavouring concentrate whose composition was not published; Fruit Acid was a strong solution of citric or tartaric acid used to give tartness; Soda Foam was a saponin preparation, usually quillaia (soap bark) or a gum, added so the drink would head up when the carbonated stream hit it. None of the three proprietary items can be bought as written, and no reliable substitution can be given for the extract, since its composition was a house matter.
- "Tonic" does not mean quinine hereFountain syrups sold as tonic in this period were marketed as invigorating rather than bitter. Some contained quinine, some kola or gentian, some nothing more than aromatics. Do not assume this tastes like tonic water.
- Fountain simple syrup is not bar simple syrupTrade simple syrup of the era ran close to saturation, on the order of a pound of sugar to well under a pint of water, so it poured thick and kept without spoiling. A modern 1:1 syrup is far thinner and will taste watery at fountain dispensing rates.
- MeasuresAll quantities are fluid ounces and liquid quarts; 2 quarts is 64 fl oz. The finished batch is about 69 fl oz.
- Yield and dispensingStandard fountain practice was 1 to 1.5 fl oz of syrup per glass, topped with about 6 oz of carbonated water. That makes roughly 45 to 70 drinks from this batch.
- Order of mixingThe recipe specifies no order. It makes sense to add the acid and the foam to the syrup last and to stir rather than shake, since beating air into a saponin syrup during mixing wastes foaming power that is meant to appear in the glass.
- KeepingHeavy syrup at this sugar concentration is largely self-preserving, but the acid attacks metal. Glass or stoneware, stoppered, kept cool and dark.
Soda books of this type were written for the dispenser behind a marble counter, not for the home, and they read like an inventory because that is what they were: the fountain trade ran on branded concentrates bought from wholesale supply houses. The syrup itself was assembled on the premises, and the pharmacist or fountain man who owned the book was expected to know already how much water to draw and how hard to gas it. "Tonic" belonged to the drugstore side of the business, a reminder that American soda fountains grew out of pharmacies and that a glass of something fizzy was long sold on the promise of doing you good as much as tasting pleasant. Foaming agents drawn from quillaia bark were standard in the trade for decades; they remain permitted in beverages under quantity limits, and the real obstacle to reassembling a formula like this one from a modern shelf is that the branded concentrates it calls for have vanished.