barbotine vs engobe

barbotine

noun
  • A soft clay used for moulding or decorating pottery 

engobe

noun
  • A non-black clay slip coating applied to a ceramic body to give it decorative color or improved texture. 

  • A clay slip which is colored with metal oxides or stains, used for coating the surface of a pot either before or after bisque firing. 

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