Guida applicativa
Silice colloidale nella fusione a investimento: guida pratica per importatori
Learn how to select and source colloidal silica for investment casting shell building.
## Overview
Colloidal silica is the most widely used binder in investment casting shell building.
## Grade selection
| Grade | Particle Size | SiO₂ | pH | Primary Use |
|-------|--------------|------|-----|-------------|
| Standard alkaline | 8–12 nm | 30% | 9.5–10.5 | Primary slurry |
| Fine particle | 5–8 nm | 30%–40% | 9.5–10.5 | Facing layers |
| Large particle | 20–50 nm | 20%–30% | 9.0–10.0 | Backup layers |
## Slurry preparation checklist
1. Verify SiO₂ concentration — adjust to target (25%–30%)
2. Measure viscosity — target 20–40 seconds (Zahn cup #4)
3. Check pH — maintain 9.0–10.5
4. Add refractory flour gradually
5. Mix 30–60 minutes
6. Degas if needed
7. Test density (1.8–2.2 g/cm³)