Water Retention Capacity
Water Retention Capacity of Expanded Perlite — Capillarity & Drainage Dynamics
Water retention capacity describes how much water expanded perlite can hold through capillary action. Typical retention is 20–40% by volume, balancing hydration and drainage in horticultural and hydroponic systems.
1. What Is Water Retention Capacity?
1.1 Capillary Water
Held in small pores.
1.2 Gravitational Water
Drains freely.
1.3 Hygroscopic Water
Minimal in perlite.
2. Typical Water Retention Values
| Grade | Retention (%) | Meaning |
|---|---|---|
| Coarse | 15–25 | High drainage |
| Medium | 20–35 | Balanced |
| Fine | 30–40 | High retention |
3. How Water Retention Is Measured
3.1 Saturation Method
Saturate → drain → measure retained water.
3.2 Volumetric Analysis
Water volume per substrate volume.
4. Factors Affecting Water Retention
4.1 PSD
Fine → higher retention.
4.2 Porosity
Higher porosity → more capillary water.
4.3 Density
Lower density → higher retention.
5. Application Performance
5.1 Horticulture
Balanced hydration.
5.2 Hydroponics
Stable moisture.
5.3 Greenhouse Cultivation
Uniform water distribution.
6. Geological Influence
- Natural porosity
- Hydration
- Glass chemistry
7. Regional Water Retention Characteristics
| Region | Retention | Notes |
|---|---|---|
| Turkey | High | Coarse + fine grades |
| Greece | Medium | Coarse PSD |
| USA | High | Fine PSD |
| Mexico | Variable | Mixed |
| Iran | High | Uniform |
8. FAQ
Q: Does perlite hold too much water?
No — drains freely.
Q: Does retention vary by grade?
Yes — PSD dependent.
Q: Why does retention vary?
Porosity and PSD differences.
