solidify vs vitrify

solidify

verb
  • To make solid; convert into a solid body. 

  • To become solid; to freeze, set. 

  • To concentrate; consolidate. 

vitrify

verb
  • To convert into glass or a glass-like substance by heat and fusion. 

  • To be converted into glass, especially through heat. 

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