Loss on Ignition (LOI) in Green Sand and Gilsonite

Loss on ignition is a simple test that tells you how much combustible material is in your sand. It is essential for controlling carbon additives.

What LOI measures

A dried sand sample is heated to about 1000°C. The weight loss represents carbon additives, organic binders and other combustibles.

Typical LOI levels

Most iron foundries keep LOI between 2% and 5%, depending on casting type.

Too high

• Excess gas, causing blowholes
• Lustrous carbon defects
• Smoke and odour

Too low

• Burn-on and penetration
• Poor surface finish

Using gilsonite

Because gilsonite has high volatile matter and low ash, it adds active carbon without as much inert build-up. Track LOI alongside volatile content.

How to measure LOI

1. Take a representative sample of prepared sand.
2. Dry at about 105 °C to remove moisture.
3. Weigh, then heat at about 1,000 °C until constant weight.
4. LOI = weight loss / dry weight × 100 %.

LOI vs. volatiles

LOI includes all combustible matter (fresh additive, burned residues, core binders). Volatile content (measured at lower temperature without air) better reflects the active additive. Track both for good control.

Control chart

Plot daily LOI and volatiles against casting defects. Patterns quickly show when additions need adjustment.

See foundry grade gilsonite and foundry dosage guide.