gradate

from WordNet (r) 3.0 (2006)

gradate
    v 1: arrange according to grades; "These lines are gradated"
    2: pass imperceptibly from one degree, shade, or tone into
       another; "The paint on these walls gradates but you don't see
       it"

from The Collaborative International Dictionary of English v.0.48

Gradate \Gra"date\, v. t. [See {Grade}.]
   1. To grade or arrange (parts in a whole, colors in painting,
      etc.), so that they shall harmonize.
      [1913 Webster]

   2. (Chem.) To bring to a certain strength or grade of
      concentration; as, to gradate a saline solution.
      [1913 Webster]