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Acaia or BOOKOO, under the kettle or the brewerBrew weight
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Recipes
Pour plans to follow on the Brew page: amounts, timings and pour speeds.
Water
Every figure is ppm as CaCO3.
Build a batch
Hardness and alkalinity are independent here: alkalinity rides on potassium, so it adds no GH. Drops go straight into the full jug. Even a 100 ppm total dose is well under 1% added volume, so there is no make-to-mark step.
The three bottles
Weigh into a volumetric flask, make to the mark with deionised water, and transfer to an amber dropper bottle. Keep them at room temperature, not in the fridge. Cold is what makes a near-saturated stock throw crystals.
Calibrate the dose
Drip into a 10 mL graduated cylinder until it reads 5.00 mL, counting drops, and repeat three times. Drop volume varies with tip geometry and squeeze rate. Assuming 0.05 mL without checking is the largest error in this whole method.
Batch 946.4 mL Dose volume 0.250 mL Doses per 250 mL bottle 1000
Working notes
- Why not one drop
- At one drop per 10 ppm the bicarbonate stock would need to be roughly 318 g/L. That is about three times the solubility of sodium bicarbonate, and still short of practical for the potassium salt. Magnesium sulfate would sit near 70% of saturation. Five drops brings every bottle into a comfortable margin.
- Sodium instead
- NaHCO3 substitutes for the potassium salt at 63.5 g/L. It is workable, but that is about two-thirds of its room-temperature solubility and closer still in a cold kitchen. The potassium salt sits near a quarter of its own limit, which is the only reason it is the default here. It also swaps 4.6 mg/L Na+ for 7.8 mg/L K+ per 10 ppm KH.
- Gypsum
- CaSO4·2H2O is not usable as a drop stock. It would need about 65 g/L against a solubility near 2.4 g/L. Calcium goes in as the chloride, and sulfate comes from the magnesium bottle.
- Keep them apart
- Never combine concentrates. Calcium plus bicarbonate at these strengths precipitates CaCO3, and a chloride-calcium stock mixed with a sulfate-magnesium stock is supersaturated in gypsum by orders of magnitude.
- What drifts
- A bicarbonate stock slowly loses CO2, which raises its pH but conserves alkalinity, so the titre you dose stays right. The real drift is hydrate water: CaCl2·2H2O is deliquescent and MgSO4·7H2O effloresces in dry storage, so a few percent of gravimetric error hides in an old bottle regardless of the balance.
- Verify
- GH by EDTA titration with Eriochrome Black T at pH 10. KH by standard acid to a bromocresol green–methyl red endpoint. One titration per stock pins down what you actually made, and settles the drop calibration at the same time.
Solubility figures are approximate room-temperature values used only to flag headroom. Verify before pushing a stock past about half the bar. Ion contributions are computed from formula masses: 10 ppm as CaCO3 is 0.0999 mmol/L of divalent hardness, or 0.200 meq/L of bicarbonate.
Labels
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Labels collect here as you divide bags into cellars, so one sheet can carry several coffees. Each label is 4 × 2 inches and 10 fit on a letter sheet. Pick a colour for each coffee.
Print the PDF at 100% scale (“Actual size”, not “Fit to page”), then cut along the grey lines.
The label
The barcode and the number under it are unique to each cellar. Use “Scan a tube” on the Brew log to photograph one and start a brew from that cellar.