Mash pH
Predicting and adjusting your mash from grain and water chemistry
Mash pH affects enzyme activity, tannin extraction, and flavor. Most brewers aim for 5.2–5.6. Too high and you extract harsh tannins. Too low and enzyme activity drops off. The recipe builder predicts your mash pH from your grain bill and water profile, and tells you how much acid or baking soda to add if it's off.
How We Calculate It
We use the proton deficit model, the current gold standard for mash pH prediction. The idea is simple: every grain adds acid to the mash, and every water ion adds alkalinity. At the correct pH, all these contributions balance out to zero. We solve for that equilibrium point.
The solver finds the pH where total proton contributions sum to zero.
Every grain has a pH fingerprint
Base malt has a distilled-water pH of ~5.7. Roasted barley drops to ~4.5. Acidulated malt is ~3.4 (it contains lactic acid). Each grain also has a buffering capacity of ~40 mEq/kg/pH, which measures how much it resists pH change. We use grain data from published sources and interpolate by color for specialty malts.
Your water fights back
Bicarbonate in your water resists the acid from grain. Calcium and magnesium help counteract this by reacting with malt phosphates (Kolbach's factors: Ca/3.5 and Mg/7). Hard water with high bicarbonate pushes pH up. Soft water lets the grain pull it down naturally.
How Accurate Is It?
Typically within ±0.1 pH for standard grain bills. Good enough to calculate water adjustments before brew day, but still worth measuring with a pH meter to calibrate for your specific system. The model works best when your water report is accurate and your grain is fresh.
Where This Comes From
The proton deficit model was developed by AJ deLange and published in the MBAA Technical Quarterly. Grain pH and buffering values are based on published malt analyses and brewing literature, including Kai Troester's work at braukaiser.com. Kolbach's calcium and magnesium factors come from mid-20th century German brewing research.
See all the numbers come together in real time.
See this in the recipe builder