| Factors | Units | Variables | Levels/Variations | ||
| Lower (−1) | Centre (0) | Higher (+1) | |||
| Amount of porogen | g | X1 | 20 | 30 | 40 |
| Size of porogen | µm | X2 | 50 | 100 | 150 |
| Amount of binder (PVA) | g | X3 | 2 | 3.5 | 5 |