ultramarine ash


From The Collaborative International Dictionary of English v.0.48:

Ultramarine \Ul`tra*ma*rine"\, n. [Cf. Sp. ultramarino. So
   called because the lapis lazuli was originally brought from
   beyond the sea, -- from Asia.] (Chem.)
   A blue pigment formerly obtained by powdering lapis lazuli,
   but now produced in large quantities by fusing together
   silica, alumina, soda, and sulphur, thus forming a glass,
   colored blue by the sodium polysulphides made in the fusion.
   Also used adjectively.
   [1913 Webster]

   Green ultramarine, a green pigment obtained as a first
      product in the manufacture of ultramarine, into which it
      is changed by subsequent treatment.

   Ultramarine ash or Ultramarine ashes (Paint.), a pigment
      which is the residuum of lapis lazuli after the
      ultramarine has been extracted. It was used by the old
      masters as a middle or neutral tint for flesh, skies, and
      draperies, being of a purer and tenderer gray than that
      produced by the mixture of more positive colors.
      --Fairholt.
      [1913 Webster]
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