Loss on Ignition (LOI) in Perlite — Thermal Stability & Purity Indicators: Loss on Ignition (LOI) represents the percentage of mass lost when perlite is heated to high temperatures (typically 900–1,000°C). LOI reflects moisture, volatile compounds, and organic residues. In expanded perlite, LOI is a key indicator of purity, thermal stability, and expansion quality.
LOI measures the mass loss of perlite during controlled high temperature heating. It includes:
1.1 Free Moisture
• Evaporates at 100–200°C
• Does not affect expansion
• Indicates storage conditions
1.2 Chemically Bound Water
• Released at 850–1,100°C
• Drives expansion
• Critical for density and porosity
1.3 Volatile Impurities
• Organics
• Carbonates
• Hydroxyl groups
High LOI may indicate contamination or incomplete pre drying.
High quality perlite typically shows 2–4% LOI.
3.1 Standard Method: ASTM C114
1. Dry sample at 105°C
2. Heat to 900–1,000°C
3. Record mass loss
4. LOI (%) = (Mass loss / Initial mass) × 100
3.2 Importance of Controlled Heating
• Too fast → spattering
• Too slow → incomplete release
3.3 LOI vs. Bound Water
• LOI includes bound water but also other volatiles.
4.1 Geological Hydration
• Older deposits → higher bound water.
4.2 Weathering
• Increases hydroxyl content.
4.3 Organic Contamination
• Increases LOI beyond normal ranges.
4.4 Storage Conditions
• Humidity increases free moisture.
5.1 Expansion Quality
• Higher LOI → better expansion → lower density.
5.2 Thermal Stability
• Low LOI → stable performance in insulation.
5.3 Filtration
• High LOI may reduce purity.
5.4 Horticulture
• LOI affects pH and chemical stability.
• Hydration history
• Cooling rate
• Glass chemistry
• Deposit age
Deposits with optimal hydration show LOI values ideal for expansion.
Q: Does high LOI always mean better expansion?
Only if volatiles are structural water, not impurities.
Q: Can LOI be reduced artificially?
Yes, through pre drying, but bound water cannot be removed.
Q: Why does bulk density vary between producers?
Differences in hydration and weathering.
Loss on Ignition (LOI) represents the percentage of mass lost when perlite is heated to high temperatures. It reflects free moisture, chemically bound water and volatile impurities. LOI is a key indicator of purity, thermal stability and expansion performance in industrial applications.