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Percolated Coffee I
Put 1 cup finely ground coffee in upper part of glass coffee pot, put 6 cups hot water in lower part. Light alcohol lamp. When water begins to boil and enters upper receptacle leave 1 minute. Remove light, while water runs back to lower receptacle, then put light back until water again boils and has risen to top. Remove and extinguish light, remove upper globe, and coffee is ready to serve.
Despite the title, this describes a vacuum (siphon) pot rather than a percolator: two glass globes, a heat source under the lower one, and steam pressure pushing water up through the grounds before vacuum pulls the brew back down. Everything about the method is still workable on a modern siphon, with a few adjustments.
- The ratio is the useful partOne cup of finely ground coffee is roughly 3 oz / 85 g, and six cups of water about 1.4 litres. That works out near 1:17, which is squarely within the range a modern brewer would use, so the recipe scales directly.
- Grind finer than you think, but not to powderSiphon pots use a cloth or glass filter and a short contact time, so a fine-medium grind is right. A true espresso grind will choke a cloth filter and pass silt through a glass one.
- Skip the second cycleThe instruction to let the water fall back and then drive it up again puts the coffee through a second round of hot extraction, which risks over-extraction. One minute in the upper globe, then remove the heat and let it draw down once, is enough.
- Heat sourceAn alcohol lamp gives a small, steady flame that is easy to pull away. A gas burner on its lowest setting or the butane burner sold with modern siphons does the same job; an electric coil is clumsy because you cannot remove the heat instantly.
- "When water begins to boil"A rolling boil is not wanted. Water enters the upper chamber at around 195-205F, and if it is boiling hard in the upper globe you will get bitterness and a violent draw-down. Lower the flame as soon as the water has risen.
- Handle the glass with respectOld glass coffee pots were not tempered as reliably as modern borosilicate. Never set a hot globe on a cold wet surface, and never heat the lower globe with less than a cup of water in it.
- YieldSix cups of water gives roughly five cups of poured coffee, since the grounds retain the rest.
Vacuum brewers of this kind date to the 1830s and 1840s in Europe and were sold through the later nineteenth century as an elegant, tableside alternative to the boiled coffee common in American households; part of the appeal was that the apparatus was glass and the operation visible. That the author calls it "percolated" appears to reflect loose period usage, in which "percolate" could cover methods that passed water through grounds held apart from the pot rather than boiling the two together. Vacuum pots were displaced over the middle of the twentieth century by electric percolators and later by drip machines, and the form was revived by specialty coffee bars in the 2000s, where the same double-globe silhouette is now called a siphon.