LEGACY RESEARCH INVENTORY — NOT CURRENT FERMUNITS DOCUMENTATION

This file is preserved as historical planning and research context. It may
contain superseded formulas, unsupported claims, approximate values, proposed
names that were never implemented, or items still awaiting authoritative source
verification. See ../README.md and the maintained reference documents in the
parent directory for current FermUnits behavior.

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          MASTER FERMENTATION CALCULATOR SPECIFICATION - PART 1: BREWING
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A technical backend manual covering sugar, density, color, bitterness,
enzymatic power, carbonation, and historical cask capacities mapped directly
to standard SI metric base, derived, and accepted non-SI units.
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1. EXTRACT, SUGAR CONCENTRATION & DENSITY (GRAVITY)
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*   Specific Gravity (SG)
    - Description: Dimensionless ratio of the weight of a volume of wort/beer to
      the weight of an equal volume of pure water at a standard temperature.
    - Core Users: Universally preferred by Homebrewers and small UK/US Craft
      Microbreweries using hydrometers.
    - Metric / SI Baseline Value: Dimensionless ratio. At standard reference
      density (1.000), mass density equals exactly 1,000 kg/m³ (SI Base: kg, m).

*   Degrees Plato (°P)
    - Description: Measures the concentration of dissolved solids as a mass
      percentage of sucrose (grams of sucrose per 100 grams of liquid).
    - Core Users: Absolute global standard for Large Commercial breweries and
      highly professional Craft/Micro operations.
    - Metric / SI Baseline Value: Mass fraction unit (1°P = 0.01 kg of sucrose / kg of solution).

*   Degrees Brix (°Brix)
    - Description: Functionally identical to Plato, measuring percentage sucrose
      by weight, derived originally from different calibration tables.
    - Core Users: Widely used by Homebrewers and small Craft/Micro brewers when
      taking raw measurements using optical or digital refractometers.
    - Metric / SI Baseline Value: Mass fraction unit (1°Brix = 0.01 kg of sucrose / kg of solution).

*   Degrees Balling (°Balling)
    - Description: The earliest mass-percentage scale for dissolved sugars, older
      than Plato and slightly less mathematically precise at high temperatures.
    - Core Users: Historical legacy. Found in traditional European breweries.
    - Metric / SI Baseline Value: Mass fraction unit (1°Balling = 0.01 kg of sugar / kg of solution).

*   Gravity Points / Gravity Units (GU)
    - Description: A simplified integer shorthand representing the fractional part
      of Specific Gravity.
    - Core Users: Homebrewers and small Craft/Micro recipe developers for raw math.
    - Metric / SI Baseline Value: Dimensionless integer scale where:
      GU = (Mass Density in kg/m³ - 1000).

*   HIGH-PRECISION CONVERSION FORMULAS:
    - SG to GU:
        GU = (SG - 1.000) * 1000
    - GU to SG:
        SG = 1.000 + (GU / 1000)
    - SG to Plato (Highly Precise ASBC Polynomial Formula):
        °P = -616.868 + (1111.14 * SG) - (630.272 * SG^2) + (135.997 * SG^3)
    - Plato to SG (Precise De Clerck Formula):
        SG = 1 + (°P / (260.5 - [°P * 0.3896]))
    - Brix to Plato (Wort Correction Factor Integration):
        °P = Brix / WCF
        (Note: Default WCF for beer is 1.04. Unfermented wort contains proteins
        and beta-glucans that skew the light refraction index compared to wine)

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2. CROSS-DISCIPLINARY HYDROMETER TEMPERATURE CORRECTION
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Most winemaking and brewing hydrometers are calibrated to 60°F (15.5°C) or 68°F
(20°C). If the fluid is hot from the brewhouse or cold from the wine cellar, you
must apply a correction factor to the Specific Gravity before running final calculations:

*   Formula (Where T is temperature in Fahrenheit):
    SG_corrected = SG_measured + ((0.000004811 * T^2) - (0.005408 * T) + 0.1292)
    - SI Base Unit Application: Standardizes measurements dynamically to prevent
      density skewing caused by thermal molecular expansion.

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3. COLOR QUANTIFICATION
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*   Standard Reference Method (SRM)
    - Description: Color density calculated via spectrophotometer by measuring the
      attenuation of light at 430 nanometers through a 0.5-inch path cell.
    - Core Users: Broadly used across all US brewing tiers.
    - Metric / SI Baseline Value: Absorbance metric. Light wavelength is 430 x 10⁻⁹ m
      (SI Base: m). Path length cell is exactly 0.0127 m.

*   Degrees Lovibond (°L)
    - Description: Legacy system based on a qualitative visual comparison of beer or
      wort samples against a series of tinted amber/yellow glass slides.
    - Core Users: Homebrewers, Craft/Micro recipe developers, and maltsters.
    - Metric / SI Baseline Value: Qualitative visual matching scale index.

*   European Brewery Convention (EBC)
    - Description: Color density calculated at 430 nanometers, utilizing a
      metric 10-millimeter (1 cm) path cell instead of an inch cell.
    - Core Users: Large Commercial breweries globally, and European Craft/Micro tiers.
    - Metric / SI Baseline Value: Absorbance metric. Light wavelength is 430 x 10⁻⁹ m.
      Path length cell is exactly 0.01 m (10 mm).

*   CONVERSION FORMULAS:
    - Lovibond to SRM:
        SRM = (1.35 * °L) - 0.6
    - SRM to EBC:
        EBC = SRM * 1.97
    - EBC to SRM:
        SRM = EBC * 0.508

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4. HOP BITTERNESS CHEMISTRY
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*   International Bitterness Units (IBU) / European Bitterness Units (EBU)
    - Description: Chemical measurement of isomerized alpha acids in liquid beer,
      where 1 IBU equals exactly 1 milligram of isomerized alpha acid per liter.
    - Core Users: Universal across all global brewing tiers.
    - Metric / SI Baseline Value: Mass concentration per volume unit.
      1 IBU = 0.001 g/L = 0.001 kg/m³ (SI Base: kg, m).
    - Conversion Formula: IBU to EBU is treated functionally as 1:1.

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5. ENZYMATIC ACTIVITY (DIASTATIC POWER)
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*   Degrees Lintner (°L or °Lintner)
    - Description: Measures the capability of malted grains to break down complex
      starches into simpler fermentable sugars under defined laboratory conditions.
    - Core Users: US Homebrewers, US Craft/Micro brewers, and North American Maltsters.
    - Metric / SI Baseline Value: Enzyme catalytic conversion index.

*   Windisch-Kolbach Units (WK)
    - Description: European standard measurement for the enzymatic power of malted grains.
    - Core Users: European Maltsters, Large Commercial breweries, and international craft fields.
    - Metric / SI Baseline Value: Catalytic conversion index related to SI derived unit Katal (mol/s).

*   CONVERSION FORMULAS:
    - Lintner to WK:
        WK = (Lintner * 3.5) - 16
    - WK to Lintner:
        Lintner = (WK + 16) / 3.5

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6. CARBONATION LEVELS
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*   Volumes of CO2 (v/v)
    - Description: The ratio of the volume of dissolved carbon dioxide gas to the
      total volume of the liquid beer container hosting it at standard temperature/pressure.
    - Core Users: US/UK Homebrewers and US/UK Craft/Micro breweries.
    - Metric / SI Baseline Value: Dimensionless volumetric ratio (1 Volume = 1 m³ gas / m³ liquid).

*   Grams per Liter (g/L)
    - Description: The physical mass of carbon dioxide gas dissolved per liter of liquid.
    - Core Users: Large Commercial breweries worldwide, and Metric European Craft/Micro sites.
    - Metric / SI Baseline Value: Mass concentration per volume (1 g/L = 1 kg/m³).

*   CONVERSION FORMULAS:
    - Volumes of CO2 to g/L:
        g/L = Volumes * 1.96
    - Grams per Liter to Volumes:
        Volumes = g/L * 0.51

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7. MODERN BREWERY PRODUCTION VOLUME
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*   US Beer Barrel (bbl)
    - Size / Description: Standard equipment capacity and production unit in North America.
    - Metric / SI Baseline Value: Volume unit. Exactly 31 US gallons / 117.34776 Liters (0.11735 m³).

*   Hectoliter (hL)
    - Size / Description: Standard unit equal to exactly 100 liters of fluid volume.
    - Metric / SI Baseline Value: Accepted Non-SI Metric Volume unit. Exactly 100 Liters (0.1 m³).

*   CONVERSION FORMULAS:
    - US Barrel (bbl) to Hectoliters (hL): 1 bbl = 1.17347 hL
    - Hectoliter (hL) to US Barrels (bbl): 1 hL = 0.85218 bbl
    - US Barrel (bbl) to US Gallons: 1 bbl = 31 US Gallons
    - US Barrel (bbl) to Liters: 1 bbl = 117.347 Liters

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8. HISTORICAL CASK VOLUMES (BREWING STANDARD)
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In 1824, the UK standardized these around Imperial Gallons. The historical sequence
builds proportionally off the foundational "Firkin".

*   Pin
    - Volumetric Size: 4.5 Imperial Gallons / 5.4 US Gallons.
    - Metric / SI Baseline Value: Volume unit. Exactly 20.4574 Liters (0.02046 m³).

*   Firkin
    - Volumetric Size: 9 Imperial Gallons / 10.81 US Gallons.
    - Metric / SI Baseline Value: Volume unit. Exactly 40.9148 Liters (0.04091 m³).

*   Kilderkin
    - Volumetric Size: 18 Imperial Gallons / 21.62 US Gallons.
    - Metric / SI Baseline Value: Volume unit. Exactly 81.8296 Liters (0.08183 m³).

*   Barrel (UK Historical / Real Ale Barrel)
    - Volumetric Size: 36 Imperial Gallons / 43.23 US Gallons.
    - Metric / SI Baseline Value: Volume unit. Exactly 163.6592 Liters (0.16366 m³).

*   Hogshead
    - Volumetric Size: 54 Imperial Gallons / 64.85 US Gallons.
    - Metric / SI Baseline Value: Volume unit. Exactly 245.4888 Liters (0.24549 m³).

*   Puncheon
    - Volumetric Size: 72 Imperial Gallons / 86.47 US Gallons.
    - Metric / SI Baseline Value: Volume unit. Exactly 327.3184 Liters (0.32732 m³).

*   Butt
    - Volumetric Size: 108 Imperial Gallons / 129.70 US Gallons.
    - Metric / SI Baseline Value: Volume unit. Exactly 490.9776 Liters (0.49098 m³).

*   CONVERSION MATRIX FOR CASK VOLUMES:
    - 1 Pin = 0.5 Firkins
    - 1 Firkin = 2 Pins = 0.5 Kilderkins = 0.25 UK Barrels
    - 1 Kilderkin = 2 Firkins = 4 Pins = 0.5 UK Barrels
    - 1 UK Barrel = 2 Kilderkins = 4 Firkins = 8 Pins
    - 1 Hogshead = 1.5 UK Barrels = 6 Firkins = 12 Pins
    - 1 Puncheon = 2 UK Barrels = 8 Firkins = 16 Pins
    - 1 Butt = 3 UK Barrels = 12 Firkins = 24 Pins
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