curdle vs vitrify

curdle

verb
  • To cause a liquid to spoil and form clumps so that it no longer flows smoothly 

  • To form curds so that it no longer flows smoothly; to cause to form such curds. (usually said of milk) 

  • To clot or coagulate; to cause to congeal, such as through cold. (metaphorically of blood) 

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 curdle and vitrify occurred in a corpus of books? (source: Google Ngram Viewer )