The Collaborative International Dictionary of English v.0.48:

Blacks \Blacks\, n. pl.
   1. The name of a kind of in used in copperplate printing,
      prepared from the charred husks of the grape, and residue
      of the wine press.
      [1913 Webster]

   2. Soot flying in the air. [Eng.]
      [1913 Webster]

   3. Black garments, etc. See Black, n., 4.
      [1913 Webster]