| Raw Material | pH in distilled water |
| Quartz #500 | 5.8 |
| Quartz #325 | 5.9 |
| Quartz #200 | 5.9 |
| Silica Mix | 5.8 |
| Cristobalite #500 | 6.2 |
| Cristobalite Milled 24 h | 6.2 |
| Vitreous Silica #100 | 6.0 |
| Vitreous Silica #325 | 6.4 |