The Collaborative International Dictionary of English v.0.48:

Impasting \Im*past"ing\, (Paint.)
   The laying on of colors to produce impasto.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Impaste \Im*paste"\, v. t. [imp. & p. p. Impasted; p. pr. &
   vb. n. Impasting.] [Pref. im- in + paste: cf. It.
   impastare, OF. empaster, F. emp[^a]ter. See 1st In- and
   Paste.]
   1. To knead; to make into paste; to concrete. "Blood . . .
      baked and impasted." --Shak.
      [1913 Webster]

   2. (Paint.) To lay color on canvas by uniting them skillfully
      together. Cf. Impasto. [R.]
      [1913 Webster]