Langelier and Ryznar indices basics
Understanding water stability indices and how they predict scaling or corrosion tendencies in coffee equipment.
- Coffee Basics Nerds
- 1 min read
Langelier and Ryznar Indices
-
Purpose:
-
Evaluate water’s tendency to form scale (deposit minerals) or corrode equipment.
-
Langelier Saturation Index (LSI):
-
Positive LSI → water tends to form scale.
-
Negative LSI → water tends to be corrosive.
-
Zero → water is balanced.
-
Ryznar Stability Index (RSI):
-
RSI < 6 → scale-forming tendency.
-
RSI > 7 → corrosive tendency.
-
RSI 6–7 → fairly stable.
-
Calculation Basics:
-
Both indices consider pH, temperature, total hardness, alkalinity, and TDS.
-
Practical Relevance:
-
Helps roasters and baristas adjust water treatment to protect boilers, espresso machines, and coffee flavor.
-
Guides remineralization and softening strategies.
-
Best Practice:
-
Monitor indices regularly alongside titration and TDS measurements for a complete water profile.