Tuesday, September 7, 2010

Making Blue – or what to do if you don't have enough lapis lazuli

'Through the atmosphere the universe tones towards us in the colour blue and according to the thickness of the air, takes on every grade of blue until it goes over to black-violet on the mountain tops'

-Goethe 'Theory of Colours'

The above quote makes me think of the Van Gogh painting 'The Starry Night' – one of my favorites. I love the shades of blue (I love the swirls too but, that makes up a different story). So what makes paint blue? Typical pigments used include Azurite, Cerulean Blue, Cobalt Blue, Prussian Blue and Ultramarine which was once made from lapis lazuli.

Although there are other natural blues that can be used in pigments, lapis lazuli intrigues me the most. Years ago, I read a book on natural colours where the author journeyed to Afghanistan (in safer times) to find lapis lazuli. I don't have the book at hand, so I can't quote from it, but ever since then I've thought lapis lazuli had a fantastic story, I even like saying 'lapis lazuli'. Powdered lapis was used as eyeshadow by Cleopatra – what could be more exotic than that?

Lapis lazuli has always been prized for its intense blue color. It has been mined from Afghanistan for over 6,000 years and there are other sources around Lake Baikal in Siberia. Lapis lazuli is classified as a rock composed of more than one mineral. Since it polishes well, it can be made into jewelry, carvings, boxes, mosaics, ornaments, and vases. In ancient Egypt, lapis lazuli was favored for inclusion on amulets and ornaments such as scarabs. To answer my paint question, lapis lazuli was also ground and processed to make the pigment ultramarine.

So what if lapis lazuli wasn't available (or too expensive)? Before modern synthetic colours became available there were several options.

Egyptian Blue is a pigment that was made and used by Egyptians for thousands of years and may even be the first synthetic pigment. In Egyptian it's called 'hsbd-iryt', which translates to 'artificial lapis lazuli'. Although it's only one of many components, copper is what makes Egyptian Blue blue. The exact hue of blue can range from light to dark depending on how it is made. Egyptian Blue coloured stone, wood, plaster, papyrus, and canvas. It was also used in objects like cylinder seals, beads, scarabs, inlays, pots and statuettes. Unfortunately, when the Roman era ended, knowledge on how to make Egyptian Blue was lost. Egyptian blue has been found on objects from all over the Roman Empire and may have been independently discovered in places like ancient China.

At least 2,000 years ago a synthetic blue turned up in China. Chinese Blue and Egyptian Blue have the same basic structure and have very similar properties. The difference is that Egyptian Blue contains calcium where Chinese Blue has barium. Was this Chinese Blue produced from knowledge of Egyptian Blue making it's way along the silk road? There are theories that lean both ways.

Another ancient blue comes from pre-columbian mesoamerica and examples are still blue today. Maya Blue is a organic-inorganic hybrid that was made by heating indigo and a fibrous clay together. This method worked so well it is an active area of research today.

Back to lapis lazuli. Lapis lazuli's use as a pigment in oil paint ended in the early 19th century when a chemically identical synthetic variety, often called French Ultramarine, became available.

No comments:

Post a Comment