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          MASTER FERMENTATION CALCULATOR SPECIFICATION - PART 4: SAKE
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A technical backend manual covering the Nihonshudo dryness index, traditional
Japanese volumetric units, rice polishing metrics, and titration acidity math
mapped directly to standard SI metric base and derived units.
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1. DRYNESS INDICES & THE NIHONSHUDO SCALE
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*   Nihonshudo (Sake Meter Value - SMV)
    - Description: A custom specific gravity scale indicating the dryness or
      sweetness of the sake. It measures the density of finished sake compared
      to pure water at 15°C (59°F). Because alcohol is lighter than water,
      positive values (+4) signify lower density (drier sake), while negative
      values (-2) signify higher residual sugars (sweeter sake).
    - Core Users: Universal across all premium sake breweries (Kura), export
      traders, and consumer labeling.
    - Metric / SI Baseline Value: Inverse density-derived index. At a reference
      water density of 1.000 (1,000 kg/m³), the SMV value is exactly 0.

*   HIGH-PRECISION CONVERSION FORMULAS:
    - Specific Gravity (SG) to Nihonshudo (SMV):
        SMV = (1443 / SG) - 1443
    - Nihonshudo (SMV) to Specific Gravity (SG):
        SG = 1443 / (SMV + 1443)
    - Example Application: An SG of 0.9972 maps to an SMV of +4.0 (Bone Dry).
      An SG of 1.0020 maps to an SMV of -2.8 (Sweet).

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2. TECHNICAL ACIDITY BALANCING (SANDO & AMANDO)
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*   Sando (Sake Acidity Metric)
    - Description: Measures the concentration of organic acids (succinic, lactic,
      and malic) in sake. Distinct from wine titratable acidity, Sando is reported
      as a raw titration factor rather than a mass-per-liter value.
    - Calculation: The volume (in milliliters) of a 0.1M Sodium Hydroxide (NaOH)
      chemical solution required to neutralize exactly 10 mL of filtered sake.
    - Metric / SI Baseline Value: Volumetric titration index ($10^{-5}\text{ m}^3$ solution titration ratio).
      An average premium sake features a Sando value between 1.2 and 1.7.

*   Amando (Sweetness-Acidity Ratio Index)
    - Description: A calculated balance value used by brewers to evaluate the
      perceived balance between sugar concentration and structural tartness.
    - High-Precision Balance Formula:
        Amando = (Nihonshudo / 10) - Sando
    - Metric / SI Baseline Value: Dimensionless sensory tracking balance index.

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3. RICE ARCHITECTURE & PRODUCTION METRICS
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*   Seimaibuai (Rice Polishing Ratio)
    - Description: Measures the mass percentage of the raw sake rice grain that
      remains after the outer layers of fat and protein are milled away.
    - Core Users: Absolute classification standard. Determines legal grades
      like Honjozo ($\le$ 70%), Ginjo ($\le$ 60%), and Daiginjo ($\le$ 50%).
    - Metric / SI Baseline Value: Mass fraction percentage unit. Calculated as:
      (Milled Grain Mass in kg / Raw Grain Mass in kg) * 100 (SI Base: kg).

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4. TRADITIONAL JAPANESE CAPACITY & BOTTLING VOLUMES
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Sake brewing facilities evaluate batch capacities, raw water requirements, and
production tax compliance using legacy volumetric units dating back to the Edo period.

*   Koku (石)
    - Volumetric Size: Exactly 180.39 Liters / 47.65 US Gallons.
    - Description: The bedrock commercial volume unit used to measure total cellar
      capacity, government facility licenses, and yearly production output.
    - Metric / SI Baseline Value: Volume unit. Exactly 180.39 Liters ($0.18039\text{ m}^3$).

*   To (斗)
    - Volumetric Size: Exactly 18.039 Liters / 4.76 US Gallons.
    - Description: Equivalent to exactly one-tenth of a Koku.
    - Metric / SI Baseline Value: Volume unit. Exactly 18.039 Liters ($0.018039\text{ m}^3$).

*   Sho (升)
    - Volumetric Size: Exactly 1.8039 Liters / 0.476 US Gallons.
    - Description: Equivalent to exactly one-hundredth of a Koku.
    - Metric / SI Baseline Value: Volume unit. Exactly 1.8039 Liters ($0.0018039\text{ m}^3$).

*   Gou (合)
    - Volumetric Size: Exactly 180.39 Milliliters / 6.10 US Fluid Ounces.
    - Description: Equivalent to exactly one-thousandth of a Koku. It is the single
      serving size standard for traditional wooden sake cups (Masu).
    - Metric / SI Baseline Value: Volume unit. Exactly 180.39 mL ($0.00018039\text{ m}^3$).

*   Isshobin (一升瓶)
    - Volumetric Size: Exactly 1.8 Liters.
    - Description: The universal glass bottle size used for packing premium sake.
      Loosely derived from the historical Sho unit but rounded to a clean metric standard.
    - Metric / SI Baseline Value: Accepted Non-SI Metric Volume unit. Exactly 1.8 L ($0.0018\text{ m}^3$).

*   CONVERSION MATRIX FOR SAKE VOLUMES:
    - 1 Koku = 10 To = 100 Sho = 1,000 Gou
    - 1 To   = 0.1 Koku = 10 Sho  = 100 Gou
    - 1 Sho  = 0.01 Koku = 0.1 To  = 10 Gou
    - 1 Gou  = 0.001 Koku = 0.01 To = 0.1 Sho
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