5 min read · Updated 23 July 2026
Glass Grade vs Foundry Grade Silica Sand: Key Differences
Glass grade and foundry grade silica sand are optimised for different things. Glass grade is chosen for chemical purity — 99.5%+ SiO₂ and very low iron (Fe₂O₃ below 0.02%) — so glass is clear. Foundry grade is chosen for physical performance in casting — refractoriness, grain shape and a target AFS grain fineness — rather than maximum purity.
What glass grade optimises for
Glassmakers need sand that melts into clear, homogeneous glass. That means high SiO₂, very low iron, and controlled sizing for even melting. Processing usually includes washing, magnetic separation and precise sizing.
What foundry grade optimises for
Foundries pack sand into moulds and cores around molten metal. The sand must withstand high temperatures (refractoriness), let gases escape (permeability) and hold shape, so grain shape and a consistent AFS grain fineness number matter more than absolute purity.
Side-by-side
The essentials at a glance:
| Property | Glass grade | Foundry grade |
|---|---|---|
| Priority | Chemical purity | Physical performance |
| SiO₂ | 99.5%+ | High |
| Iron (Fe₂O₃) | Below 0.02% | Less critical |
| Key metric | Purity / clarity | AFS grain fineness, refractoriness |
| Use | Container, flat, specialty glass | Iron, steel, aluminium casting |