The Fresco of Many Colors: Plaster & Pigmentation

Let us take a moment to appreciate the beautiful colors on the fresco. The chemical components that make a fresco and the color that sets into the fresco to create a beautiful work of art, have been heavily researched. Historians, archaeologists, and scientists are constantly asking probing questions to know more about the way the Mycenaeans (and other cultures for that matter) created these long-lasting pieces of art.

A question scholars ask themselves is: what was the plaster made out of? Archaeologists and scientists together have been fascinated for many years by the way things were created in antiquity. Archaeologist Mark Cameron and team analyzed 124 plaster samples to determine the chemicals required to make Middle Bronze Age Aegean frescoes; their test included an analysis of the ‘Ladies in Blue’ fresco.

The most common scientific test used to determine the materials required to make plaster is the x-ray diffraction (XRD). About 10 grams of a plaster fragment is all that is required to complete a test. In order to better understand the relation of the plaster to its archaeological context, 300 grams of earth was analyzed with each sample. Plaster fragments from many palatial center frescoes have been tested using this method. Cameron, M.A.S. et al. (1977). "Scientific Analyses of Minoan Fresco Samples from Knossos.", The Annual of the British School at Athens 72: 127.

Scientific testing can determine not only what the plaster is made of, but can also determine traces of aluminum, magnesium, and iron. Cameron, M.A.S. et al. (1977). "Scientific Analyses of Minoan Fresco Samples from Knossos.", The Annual of the British School at Athens 72: 129. The Ladies in Blue fresco, like other Middle Bronze Age Aegean frescoes, are made of limestone, which in scientific terminology is known as Calcium Carbonate (CaCO3).Brysbaert, A. (2007). “Murex Uses in Plaster Features in the Aegean and Eastern Mediterranean Bronze Age.”, _Mediterranean Archaeology and Archaeometry,. 7 (2): 32.

The next question that follows is: where did the Mycenaeans get their limestone from? Archaeological evidence shows that limestone deposits were found outside of the Knossos palatial center, to the southwest in the Gypsadhes Hill. Cameron, M.A.S. et al. (1977). "Scientific Analyses of Minoan Fresco Samples from Knossos.", The Annual of the British School at Athens 72: 170.

While it is good to know what the plaster was made of and where it could be found, we also ask why. Why would the Mycenaeans use limestone for plaster? Well, not only was lime plaster durable, it was also easier to paint frescoes on a softer surface. Lime plaster needed about 7-15 days to harden, which allowed artists time to complete intricately designed and detailed frescoes. Cameron, M.A.S. et al. (1977). "Scientific Analyses of Minoan Fresco Samples from Knossos.", The Annual of the British School at Athens 72: 154.

Knowing the resources Mycenaeans had to work with and knowing where these resources could be found, gives scholars more insight to the Mycenaeans, including their daily life practices. From plaster and pigmentation testing, we now know just how amazingly intelligent and advanced the Mycenaeans were at creating such frescoes.

Can you believe that a certain temperature was needed to fire the powdered limestone and turn it into usable plaster for artwork? 900 degrees Celsius was needed for 3-4 days just to make the plaster correctly. The more lime plaster was added, the smoother and whiter the surfaces were for painting.For more information about the production process of plaster, see Brysbaert, A. (2007). “Murex Uses in Plaster Features in the Aegean and Eastern Mediterranean Bronze Age.”, _Mediterranean Archaeology and Archaeometry,. 7 (2): 33.; Cameron, M.A.S. et al. (1977). "Scientific Analyses of Minoan Fresco Samples from Knossos.", The Annual of the British School at Athens 72: 149.

Scientific tests have shown that no organic solvent to bind the pigment to the plaster was used. Yet after all this time, the colors do not bleed from cold or boiling water. The pigment is truly cemented into the plaster. Cameron, M.A.S. et al. (1977). "Scientific Analyses of Minoan Fresco Samples from Knossos.", The Annual of the British School at Athens 72: 128, 160.

Which begs the question: what was each pigment made from? Alas, perhaps that is a question for another day.