liquefy vs mezzotint

liquefy

verb
  • To distort and warp an image. 

  • To become liquid. 

  • To make into a liquid. 

mezzotint

verb
  • To make such etchings 

noun
  • A form of intaglio etching in which a metal plate is roughened evenly and then smoothed to bring out an image. 

  • An etching or print made using this method. 

How often have the words liquefy and mezzotint occurred in a corpus of books? (source: Google Ngram Viewer )