The Chemistry of the Book of Kells

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The Book of Kells is a spectacularly illuminated gospel manuscript dating from around 800AD and held in Trinity College library in Dublin. Some idea of the colours achieved can be seen below. 

I thought it would be of interest to list how these colours were achieved.

  1. Black ink was made from oak-galls mixed with iron sulfate and acetic acid from wine or vinegar. Carbon-black ink was used less frequently
  2. Greens made by mixing arsenic sulfide and indigo (extracted from the Woad plant) or using verdigris, which is a copper carbonate or chloride.
  3. Red dots were made from red lead, or Pb3O4.
  4. Blue used indigo, not lapis lazuli.
  5. White was gypsum or calcium sulfate.
  6. Yellow was arsenic sulfide, known as auripigmentum since it had a lustrous golden quality.
  7. Purple came from a lichen (Roccella tinctoria) which is better known to chemists as a source of litmus; the basic chromophore of which is 7-hydroxyphenoxazone.

If you ever visit Dublin, do go and see the manuscript for yourself.

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