The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bluing \Blu"ing\, n.
   1. The act of rendering blue; as, the bluing of steel.
      --Tomlinson.
      [1913 Webster]

   2. Something, as indigo or other preparations, used to give a
      bluish tint, especially to white clothing when being
      washed.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

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