Monday, June 25, 2012

Pigment Class

  Last weekend I got the opportunity to teach a class at the known world heraldic and scribal symposium. I chose to teach a class titled "Mineral Pigment determination in Medieval Illuminated manuscripts by Raman Spectroscopy". Obviously, this is a very modern method to determine the pigments used on manuscripts. I was a little nervous about teaching that in a reenactment setting. I was not certain how it would go over. As it turned out, I did not have to worry. The people that came were very interested. up until recently, by which I mean the last 10 years, we were dependent on the look of the pigments under microscopes to guess how they were made. There are also some treatises written before the 17th century which explained how to make pigments. From these two clues, we have been theorizing on the makeup of pigments used in medieval illuminated manuscripts.
  Ten years ago, improvements in the portability of Raman Spectroscopes made it possible to bring the technology to the manuscripts. Over these last 10 years, about 18 papers have been accepted by scientific journals on the subject, mainly in the Journal of Raman Spectroscopy and Chimica Acta part A. I attempted to review these papers and draw some conclusions from their findings.

  The earliest manuscript I found a paper on is the Book of Kells, in a paper titled "The Examination of the Book of kells using Micro-Raman Spectroscopy" by Bioletti, et al published in the Journal of Raman Spectroscopy. This specific piece has been studied repeatedly to find how it was made. The previous 3 studies had theorized a total of 23 pigments that could have been used in its preparation. Then they put it unde the laser of the spectroscope. There were 2 pigments which could not be identified, including a pink and a yellowish brown. The natural pigments, those made from plant material, tend to fluoresce which subjected to the procedure and swamp the minimal signal derived from the Raman active compounds. However, some fascinating information was collected. The red pigments were made with red lead, while the yellow is orpiment. Interestingly the blue is all indigo. There is no indication of Lazurite, the mineral preoduced by grinding Lapis Lazuli, in the Book of Kells. The green was a mixture of orpiment and indigo, called vergaut, and there is a purple which is probably orcein.  Possibly, the most interesting is that the white pigment is derived from gypsum. White lead was quite in a great many of the other illuminated manuscripts tested, adn even shows up in the Lindisfarne gospels. However, the Book of Kells only has gypsum in the areas tested in the procedure.

  Therefore, one of the most beautiful early examples of mauscript ornamentation has a paltry 7 or 8 pigments making up its palette.

Book of Kells contains

Red - red lead
yellow - orpiment
Green - vergaut
Blue - indigo
Purple - Orcein
White - gypsum

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