2.3 The SCA Brewing Control Chart
Key Takeaways
- The SCA Brewing Control Chart plots Extraction Yield (18.0% - 22.0%) on the X-axis against Strength / TDS (1.15% - 1.45%) on the Y-axis.
- The chart's diagonal lines are coffee-to-water ratios by weight running 1:12 to 1:22 (not g/L gridlines); SCA's separately published Golden Cup brewing ratio is 55 g of coffee per litre of water, ±10%.
- The chart divides extraction space into 9 distinct zones, surrounding the centered Golden Cup target box.
- High TDS with low EY indicates a strong, under-extracted brew corrected by grinding finer or widening the brew ratio (adding more water).
- Low TDS with high EY indicates a weak, over-extracted brew corrected by grinding coarser or narrowing the brew ratio (using less water).
2.3 The SCA Brewing Control Chart
Quick Summary: The SCA Brewing Control Chart is a two-dimensional graph plotting Extraction Yield (18.0%–22.0% X-axis) against Strength/TDS (1.15%–1.45% Y-axis). Diagonal brew-ratio lines — printed on the current chart as coffee-to-water ratios by weight from 1:12 to 1:22 — guide baristas in diagnosing extraction errors and adjusting grind size, dose, and water contact time.
Developed originally in the 1950s by Dr. Earl Lockhart at the Coffee Brewing Institute and continually refined by the Specialty Coffee Association, the SCA Brewing Control Chart is the fundamental graphical tool of coffee science. It maps the relationship between beverage strength (TDS %), extraction efficiency (EY %), and brewing formula ratio, allowing baristas to plot extractions visually and make precise tactical recipe adjustments.
Anatomy of the Brewing Control Chart
The Brewing Control Chart is structured around two orthogonal axes and a series of intersecting diagonal lines:
- Horizontal Axis (X-Axis) — Extraction, Solubles Yield (%): On the current published chart (Version 3, revised March 2019) the axis runs from 14% to 26%. Solid vertical boundary lines mark the target ideal extraction range of 18.0% to 22.0%.
- Vertical Axis (Y-Axis) — Strength, Solubles Concentration (%): The axis runs from 0.90% to 1.80%. Dashed horizontal boundary lines mark the ideal strength window of 1.15% to 1.45%, and the box they enclose is labelled SCA Ideal on the chart itself.
- Diagonal Brew Ratio Lines: Straight lines sloping upward from left to right, each representing one fixed brewing formula. On the current SCA chart these are labelled as coffee-to-water ratios by weight (g:g or oz:oz) running from 1:12 through 1:22 — not in grams per litre. The chart carries the conversion note 1 L = 963 g at 93°C, so a 1:18 line is roughly 55 g of coffee per litre of brewing water and a 1:16 line is roughly 60 g/L.
Exam trap: candidates routinely misremember the diagonals as g/L gridlines. SCA's Golden Cup brewing ratio is quoted separately as 55 g of coffee per litre of water, ±10% (about 50–60 g/L); the chart's own diagonals are dimensionless weight ratios.
The intersection of the ideal Extraction Yield box (18–22%) and ideal Strength box (1.15–1.45%) forms a central rectangle known as the Golden Cup Target Zone.
Strength / TDS (%)
1.80% │ [Strong / Under] │ [Strong / IDEAL] │ [Strong / Over]
1.45% ├──────────────────┼──────────────────┼──────────────────┐
│ │ GOLDEN CUP │ │ <-- Target Zone
1.15% ├──────────────────┼──────────────────┼──────────────────┘
0.80% │ [Weak / Under] │ [Weak / IDEAL] │ [Weak / Over]
└──────────────────┴──────────────────┴──────────────────
18.0% 22.0% Extraction Yield (%)
The Nine Extraction Zones
By superimposing the 18–22% EY boundaries and 1.15–1.45% TDS boundaries, the chart creates 9 distinct analytical zones. Understanding these zones allows baristas to translate refractometer numbers directly into recipe adjustments:
- Golden Cup Ideal (Target Box): EY 18.0%–22.0%, TDS 1.15%–1.45%. Optimal balance of sweetness, acidity, strength, and mouthfeel.
- Strong & Under-Extracted: TDS >1.45%, EY <18.0%. Concentrated but under-developed; sharp, sour, intense.
- Strong & Ideal EY: TDS >1.45%, EY 18.0%–22.0%. Well-extracted but very heavy/intense; needs dilution or wider ratio.
- Strong & Over-Extracted: TDS >1.45%, EY >22.0%. Concentrated and bitter; harsh, dry, heavy.
- Ideal Strength & Under-Extracted: TDS 1.15%–1.45%, EY <18.0%. Good strength but sour, grassy, lacking sweetness.
- Ideal Strength & Over-Extracted: TDS 1.15%–1.45%, EY >22.0%. Good strength but bitter, dry, astringent.
- Weak & Under-Extracted: TDS <1.15%, EY <18.0%. Watery and sour; hollow, thin, unbalanced.
- Weak & Ideal EY: TDS <1.15%, EY 18.0%–22.0%. Excellent taste balance but watery body; needs more coffee dose.
- Weak & Over-Extracted: TDS <1.15%, EY >22.0%. Watery yet bitter and dry; thin, astringent finish.
Systematic Variable Adjustment Protocols
When a measured brew falls outside the Golden Cup box, baristas adjust specific recipe variables to shift the coordinates into the target zone. The golden rule of extraction dialing is: change only one variable at a time.
Target Movement Vectors on Chart:
• Grind Finer ===> Shifts Right (+ EY) and Up (+ TDS)
• Grind Coarser ==> Shifts Left (- EY) and Down (- TDS)
• Increase Dose ==> Shifts Up (+ TDS) with minimal horizontal shift
• Decrease Dose ==> Shifts Down (- TDS) with minimal horizontal shift
Scenario 1: Coffee is Strong & Under-Extracted (Zone 2)
- Coordinates: TDS 1.60%, EY 16.5% (Ratio too tight, grind too coarse).
- Diagnosis: Too much coffee dose per water volume, but coarse grind prevented full yield.
- Correction: Grind finer to increase surface area and contact time (moves EY right toward 20%), or increase water volume (widen brew ratio) to reduce TDS down into the target box.
Scenario 2: Coffee is Weak & Over-Extracted (Zone 9)
- Coordinates: TDS 0.95%, EY 23.5% (Ratio too wide, grind too fine).
- Diagnosis: Insufficient coffee dose per water volume, brewed too long through fine grounds.
- Correction: Grind coarser to shorten contact time and reduce yield (moves EY left into 18–22%), and increase dry coffee dose (narrow brew ratio) to raise TDS up into 1.15–1.45%.
Troubleshooting Chart Zones & Corrective Actions
| Measured Zone | Measured Metrics | Primary Sensory Characteristics | Primary Root Cause | Barista Corrective Action |
|---|---|---|---|---|
| Zone 2: Strong / Under | TDS >1.45%<br/>EY <18.0% | Sharp sourness, heavy body, salty notes, quick finish | Grind size too coarse; coffee dose too high | Grind finer to push yield right; widen brew ratio to lower TDS |
| Zone 4: Strong / Over | TDS >1.45%<br/>EY >22.0% | Intensely bitter, astringent, heavy, burnt notes | Grind size too fine; brew ratio too tight | Grind coarser to reduce yield; increase water volume to lower TDS |
| Zone 7: Weak / Under | TDS <1.15%<br/>EY <18.0% | Watery, sour, thin, hollow mid-palate, tea-like | Brew ratio too wide; grind size too coarse | Increase dry dose (narrow ratio); grind finer to increase yield |
| Zone 9: Weak / Over | TDS <1.15%<br/>EY >22.0% | Watery body, harsh dry finish, astringent aftertaste | Brew ratio too wide; grind size excessively fine | Grind coarser to lower yield; increase dose to raise TDS |
| Zone 1: Golden Cup | TDS 1.15–1.45%<br/>EY 18–22% | Vibrant acidity, rich sweetness, balanced body, clean finish | Optimal grind size, contact time, and brew ratio | Maintain recipe; log parameters for quality control |
On the SCA Brewing Control Chart, what variable is plotted on the horizontal (X) axis?
A brewed filter coffee tests at 1.65% TDS and 16.0% EY. Which zone of the Control Chart does this beverage occupy, and how should the barista adjust?
What brew ratio range in grams per Liter (g/L) represents the standard SCA Golden Cup target formula for filter coffee?
If a barista keeps dry coffee dose and brew water volume constant, what effect does grinding finer have on chart coordinates?