blacken in WordNet English dictionary

1. make or become black
   "The smoke blackened the ceiling"; "The ceiling blackened"
   blacken  melanize  melanise  nigrify  black 
   
2. burn slightly and superficially so as to affect color
   "The cook blackened the chicken breast"; "The fire charred the ceiling above the mantelpiece"; "the flames scorched the ceiling"
   char  blacken  sear  scorch