| No. | 1 | 2 | 3 | 4 | 5 | 6 |
| Factor name | Size/mesh | Concentration1) | soaking time/min2) | heating temperature/˚C | heating time/min | pH value |
| level 1 | 10 | 1 | 10 | 50 | 20 | 5.00 |
| level 2 | 50 | 5 | 30 | 60 | 40 | 6.00 |
| level 3 | 100 | 10 | 60 | 70 | 60 | 7.00 |
| level 4 | 150 | 15 | 90 | 80 | 80 | 8.00 |
| level 5 | 200 | 25 | 120 | 90 | 120 | 9.00 |