nigrification

from The Collaborative International Dictionary of English v.0.48

Nigrification \Nig`ri*fi*ca"tion\, n. [L. nigrificare to
   blacken; niger black + -ficare (in comp.) to make. See
   {-fy}.]
   The act or process of making black. [R.] --Johnson.
   [1913 Webster]