| fire blacken | 1.38 | Fire had blackened the field. | ||
| soot blacken | 0.66 | ... a wall blackened by soot. | ||
| smoke blacken | 0.59 | Smoke blackened the facade of the building. | ||
| sky blacken | 0.46 | Skies blackened throughout the day. | ||
| frost blacken | 0.39 | When frost has blackened the tops, cut them back to two inches above the soil. |