🌿 Hop Storage Index (HSI) Decay
Models real-time alpha acid degradation based on variety HSI, package oxygen permeability, storage temperature, and age.
📖 How This Brewing Math Works (ASBC HSI Model)
FreshHops models hop acid decay according to standard ASBC (American Society of Brewing Chemists) empirical kinetics:
AA_effective = AA_initial × exp(-k_effective × t)
Where k_base = -ln(1 - HSI) × 2, scaled by empirical storage temperature coefficients (C_temp = 0.12 at 0°F vs 1.00 at 68°F) and oxygen barrier permeability coefficients (C_pack = 0.15 for sealed mylar vs 1.00 for polyethylene bags).
🌡️ Strike Water Temperature
Calculate exact hot water strike temperature to hit your target mash rest without under- or over-shooting.
📖 How This Brewing Math Works (Thermodynamic Enthalpy)
Grain specific heat is approximately 0.4 cal/(g·°C) compared to water's 1.0 cal/(g·°C) (a 0.2 ratio in imperial units):
StrikeTemp = (0.2 / Ratio) × (TargetTemp - GrainTemp) + TargetTemp + TunOffset
Accounting for vessel thermal mass prevents the common 3–5°F temperature drop during dough-in.
🍺 Alcohol by Volume (ABV) & Attenuation
Calculate exact alcohol content (ABV & ABW), attenuation rates, and 12 oz calories from Original Gravity (OG) and Final Gravity (FG). Supports Specific Gravity (SG), °Plato, and °Brix.
📖 How This Brewing Math Works (Hall Equation, Balling Real Extract & Calories)
Standard brewing math uses ABV = (OG - FG) × 131.25, which assumes a fixed fermentation efficiency and constant alcohol density. For beers above 1.060, FreshHops defaults to the Hall High-Gravity Equation:
ABV = [ (76.08 × (OG - FG)) / (1.775 - OG) ] × (FG / 0.794)
Real Extract (RE) accounts for ethanol's lighter-than-water specific gravity skewing hydrometer readings:
RE = 0.1808·OE + 0.8192·AE.
12 oz Calories are computed according to standard ASBC guidelines:
Calories = [ (6.9 × ABW) + 4.0 × (RE - 0.1) ] × FG × 3.55.
🔬 Refractometer Alcohol Correction
Corrects for ethanol's optical distortion in fermented wort. Supports °Brix, °Plato, and Specific Gravity (SG) inputs.
📖 How This Brewing Math Works (Terrill & Hall Equations)
Ethanol has a higher refractive index than sugar solution, creating falsely high readings on an uncorrected refractometer. FreshHops applies the official Sean Terrill (2011) Cubic Model:
FG = 1.0000 - 0.0044993·RI_i + 0.011774·RI_f + 0.00027581·RI_i² - 0.0012717·RI_f² - 0.00000728·RI_i³ + 0.000063293·RI_f³
ABV is calculated using the Hall High-Gravity equation, which accurately compensates for alcohol density vs wort density across all gravity ranges.
💧 Water Chemistry & Mash pH Predictor
Calculate brewing salt additions (Gypsum, CaCl₂, Epsom) and 88% lactic acid to hit target mineral ratios and mash pH.
📖 How This Brewing Math Works (Bru'n Water Salt Kinetics)
Sulfate enhances hop bitterness perception and dryness, while chloride enhances malt fullness and sweetness. Target residual alkalinity (RA) determines the volume of food-grade 88% lactic acid needed to maintain optimal enzymatic alpha and beta-amylase activity in the 5.2–5.4 pH zone.
🍾 Carbonation & Keg PSI / Bottle Priming
Calculate exact CO₂ equilibrium regulator PSI, draft beer line length resistance, or bottle priming sugar weights.
📖 How This Brewing Math Works (Henry's Law of Gas Solubility)
Carbon dioxide solubility is governed by Henry's Law. FreshHops applies the standard ASBC polynomial equation for CO₂ equilibrium pressure:
P(PSI) = -16.6999 - 0.010105·T + 0.00116512·T² + 0.173354·T·V + 4.24267·V - 0.0684226·V²
Beer line length calculation matches line flow resistance (typically 2.2 psi/ft for 3/16" ID vinyl tubing) to overcome regulator pressure and deliver a gentle 1–2 oz/sec pour with zero foaming.
⚖️ Pre-Boil Gravity Diagnostic & Batch Saver
Kettle volume or mash efficiency off? Diagnose pre-boil gravity immediately and get exact DME additions or boil adjustments to hit target OG.
📖 How This Brewing Math Works (Gravity Points Conservation)
Gravity points (GU) represent total dissolved sugar: GU = Volume × (SG - 1.000) × 1000.
Because water evaporates during boiling while sugars remain, Predicted OG = 1.0 + (Measured Pre-Boil Points / Finished Volume) / 1000. Dry Malt Extract (DME) yields approximately 44 PPG (Points per Pound per Gallon), enabling exact kettle rescue calculations.
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