Brewing Water Calculator and Mash pH Planner

The planner combines a linear malt proton balance with a Kolbach-type water correction. This is an explicit engineering approximation, not a reproduction of a proprietary calculator.

For malt $i$, use a positive buffer magnitude $\beta_i$ in mmol H⁺ equivalents/(kg·pH) and its distilled-water pH $p_i$. Riffe & Spencer (2018), PDF pp. 2–3, derive the charge balance; their negative $B_i$ is represented here by $\beta_i=-B_i$. The selectable data are historical samples from their Tables I (p. 6) and V (p. 16).

Salt masses are converted to mmol of the stated hydrates, then to ion masses using molar masses. RO/DI dilution precedes salt additions. Alkalinity is reported as CaCO₃ with the conventional factor $50\,\mathrm{mg/mmol}$ of H⁺ equivalents. The open, heated mash approximation consumes the full reported alkalinity.

Here $V$ is L, ion concentrations are mg/L, and molar masses are mg/mmol. Kolbach uses $k_{Ca}=3.5$; Mg then uses 7. The separately reported Kolbach residual alkalinity always uses these original divisors and excludes added acid. The sensitivity input changes only the prediction's mineral response. Troester (2009), PDF pp. 7–8, observed Ca divisors 2.6–3.1 and a roughly half-strength Mg effect; these are limited experiments, not universal constants.

For stock acid, $N=1000\rho w/M$ in mmol/mL. Lactic acid delivers $N/[1+10^{(3.86-pH)}]$ H⁺ equivalents per mL. Phosphoric acid uses the full triprotic mean charge from pKa values 2.15, 7.09 and 12.32 (Sigma P6560); it releases about one proton per molecule near mash pH, not three. Known-equivalent-strength mode assumes a constant measured strength.

The solved balance is

A 28-iteration bisection brackets pH 4–7. An unbracketed case is rejected by a condition. The crossing curves show the two sides. The target dose is the nonnegative target demand divided by acid strength at the target; a negative demand instead triggers an alkali-needed message. Reference cases test a published acid-dose example, a published residual-alkalinity example and stock molarities; properties test conservation and physically required trends.

The no-acid comparison is evaluated separately and replaced by a deliberate gap outside pH 5.0–6.0. Validity conditions compare both acid-solution volumes to 1% of mash water, each salt mass/volume to its dissolution screen, and each adjusted ion concentration to the authored operating envelope. These checks are independent of the proton balance, so a mathematical pH root cannot validate an undissolved or excessively concentrated mixture.

• All reported pH values refer to a cooled sample at 20–25 °C. No fixed hot-to-cold pH offset is applied.
• Malt buffering is linear and additive near normal mash pH. Its units are mmol H⁺ equivalents per kg per pH unit, numerically the same as mEq/(kg·pH); pH itself has no unit. These are fitted effective buffers, not individual molecular species.
• The selectable malt entries are published sample data. Batch, maltster, grind and mash-time differences are not represented. Measured-data mode replaces all four sample selections; zero-mass slots contribute nothing.
• Full water alkalinity is consumed as carbonate is acidified and CO₂ escapes. This is an open-mash approximation; retained carbonate would reduce acid demand and can make this estimate overstate the needed dose.
• Calcium/magnesium acidification follows the selected empirical divisor. Stock phosphoric acid is represented by acid dissociation, with no additional calcium-phosphate precipitation model.
• Salts dissolve completely, at the labeled hydration and purity. Plain-water solubility screens reject gross overdoses, but common-ion effects and precipitation in mixed brewing water are not solved. RO/DI water is mineral-free. Acid carrier water is neglected only when both the entered and target solution volumes are at most 1% of the entered mash-water volume. Salts are entered dry, not as an unaccounted carrier solution. The ion table excludes malt-derived ions and precipitation.
• Added liquid acid is food-grade at the stated w/w strength. A known equivalent strength for an unlisted solution must be measured at the intended pH. No flavor model or fixed sulfate/chloride recipe target is imposed.
• This tool's salt mass balance, weak-acid speciation and numerical solver are derived here from stoichiometry and acid–base equilibrium. No table is inferred from malt color.

Use for ordinary infusion mashes, preferably 2.5–8 L/kg with a predicted cooled-sample pH of 5.0–6.0. The target input spans 5.0–5.8. An entered-dose prediction outside the pH 4–7 numerical bracket is withheld; this bracket is a solver limit, not a brewing recommendation. The separate no-liquid-acid comparison is displayed only at pH 5.0–6.0; otherwise its card says “Outside model range” and a warning identifies the unsupported extrapolation. This does not invalidate an acid-corrected prediction whose own conditions pass.

Typical planning uncertainty is ±0.15 pH, not a confidence interval or a guaranteed error bound. Larger errors are possible for an uncharacterized malt lot, extreme alkalinity/mineral content, unusual grind or rest times, acidulated malt, or substantial carbonate retention. The solver's tiny residual measures numerical convergence only.

Barth & Zaman (2015), DOI 10.1094/ASBCJ-2015-0621-01, report that the classic Kolbach relation requires malt-dependent modification for mashing. Their publisher abstract supports this limitation; the full paper's coefficients were not available as an open attached source and are not claimed to be implemented. The calcium control is a sensitivity exploration, not a substitute for measured calibration.

Do not apply this to sparge-water acidification, kettle/beer pH, fermentation, biological souring, extract brewing or undissolved chalk. For more than four ingredients, use a combined measured-data slot with $m=\sum m_i$, $\beta=\sum m_i\beta_i/m$ and $p_{DI}=\sum m_i\beta_i p_i/\sum m_i\beta_i$.

Choose the right bottle and hydrate, measure additions accurately, mix thoroughly, and confirm with a cooled mash sample before making further corrections.

Neglected solution volume: both the entered dose and the dose required for the target must be at most 1% of the entered mash-water volume. The dose chart ends at that same limit. The 1% threshold is an authored approximation guardrail; exceeding it requires a model that includes carrier water, not an unchanged mash ratio.

Dissolution and mineral envelope: dry-dose concentration is screened against gypsum 2 g/L, calcium chloride 740 g/L (conservatively for either hydration), Epsom salt 710 g/L, sodium chloride 358 g/L and baking soda 96 g/L. The attached physical-data sources are identified in the salt-screen table. These plain-water screens are necessary checks, not a guarantee of mixed-salt dissolution. Never treat residual-alkalinity cancellation as evidence that salts dissolve.

The planner also withholds results if the adjusted pre-reaction profile exceeds Ca 400, Mg 150, Na 300, SO₄ 600, Cl 500, or alkalinity 600 mg/L as CaCO₃ for the alkalinity row only. These are authored operating guardrails, matching the source-input envelope and constraining highly concentrated mixtures; they are not published phase boundaries, beer-style targets, or experimentally validated accuracy limits. Passing all guards does not remove the model uncertainty.