Von Post Scale
Regulatory & Scientific Terms
Also: von Post scale, humification scale, H-scale, degree of decomposition
A 10-point scale (H1-H10) measuring the degree of peat humification (decomposition). Created by Swedish geologist Lennart von Post. The standard method for classifying peat quality worldwide.
The Scale
| Grade | Description | Squeeze Test |
|---|---|---|
| H1 | Undecomposed | Clear water runs out, no plant residue |
| H2-H3 | Almost undecomposed | Slightly turbid water, plant structure intact |
| H4-H5 | Partially decomposed | Muddy water, some plant structure visible |
| H6-H7 | Well decomposed | Paste-like, little recognizable plant material |
| H8-H9 | Strongly decomposed | Thick paste, almost no plant structure |
| H10 | Fully decomposed | Completely amorphous paste |
Significance for Cosmetic Peat
Cosmetic and therapeutic peat requires H6 or higher (ideally H8). This is where humic substance concentration is highest. Below H6, peat retains too much plant structure and too few bioactive compounds for therapeutic use.
How It’s Measured
The “squeeze test” — a peat sample is squeezed in the hand. The color and turbidity of the water that runs between the fingers, and the amount of peat material that passes through, determines the H grade. Simple, field-applicable, but subjective — laboratory analysis of humic acid content provides more precise quality assessment.