| Concentration of boric acid (%) | Ultimate force (kg) | ||
| PH PVA | FH PVA | M PVA | |
| 0 | 19.9 | 22 | 20.5 |
| 0.5 | 29.8 | 24.3 | 21.7 |
| 1 | 30 | 30 | 22.5 |
| 1.5 | 36.6 | 33.2 | 23.9 |