The Processes Used

The processes used and the chemistry involved to prepare and attach pigments to surfaces in a named example of medieval or earlier artwork

Name: Saint John the Baptist with St John the Evangelist and Saint James

Date: 1365


  • Altarpiece from Florentine church owned by knights of Malta
  • Expensive commission with large amounts of ultramarine and gold


  • Much of the painting is gilded and coated with gold
  • Areas coated with mixture of iron (III) oxide and egg white before gilding
  • Gold leaf added using egg white ‘glue’ then polished
  • Floor covering was gilded then painted over with red lead in egg tempura
  • Decorative flowers and birds was coated with ultramarine in egg tempera
  • Wet paint scraped away from flowers to reveal gold below

John the Baptist: (Central)

  • Robes are crimson lake using cochineal with layers of white lead
  • Robe lining was coated with ultramarine

Saint James:

  • Ultramarine robes

Saint John the Evangelist (Left)

  • Ultramarine mixed with lead tin yellow robes
  • Some sections of book and cloak lining was blackened due to exposure to sunlight forming mercury (II) sulfide


  • Underpaint of green earth
  • Additional layer of brown and red earth
  • Green tinge to flesh due to certain factors such as years of wear caused by polishing and egg tempura growing transparent with age