porcelain clay vs terra alba

porcelain clay

terra alba

noun
  • A white earthy substance consisting of burnt gypsum and aluminium silicate (kaolin), or some similar ingredient, such as magnesia. It is sometimes used to adulterate certain foods, spices, candies, paints, etc. 

How often have the words porcelain clay and terra alba occurred in a corpus of books? (source: Google Ngram Viewer )