Source : Webster's Revised Unabridged Dictionary (1913)

Blue \Blue\, v. t. [imp. & p. p. {Blued}; p. pr. & vb. n.
   {Bluing}.]
   To make blue; to dye of a blue color; to make blue by
   heating, as metals, etc.

Bluing \Blu"ing\, n.
   1. The act of rendering blue; as, the bluing of steel.
      --Tomlinson.

   2. Something to give a bluish tint, as indigo, or
      preparations used by washerwomen.

Source : WordNet®

bluing
     n 1: used to whiten laundry or hair or give it a bluish tinge
          [syn: {blueing}, {blue}]
     2: a process that makes something blue (or bluish) [syn: {blueing}]