Egyptian Blue

What color is Egyptian blue?

The story of Egyptian blue

Egyptian blue is the oldest manufactured color on earth, and for more than a thousand years nobody could remember how to make it.

Lapis lazuli was the blue the Egyptians wanted on everything, and they could not dig up enough of it, so they cooked a substitute. The oldest trace is on an alabaster bowl from about 3250 BC; by the Fourth Dynasty, the pyramid builders, it was being made on purpose. The recipe is quartz sand, a copper mineral, lime and a pinch of natron, fired at 800 to 1000 degrees Celsius for hours. Out comes a cake of blue crystals, CaCuSi4O10. Their own name for it meant artificial lapis. Grind it coarse for dark, fine for pale; too much lime and it comes out green.

Rome ran on it. Vitruvius, in the first century BC, left the only surviving recipe: sand, copper and natron, rolled into balls and fired. The Romans called it caeruleum, from caelum, the sky, which is where cerulean comes from. Then, in the fourth century AD, people stopped making it and the recipe died with them. A pot of unused powder came out of Pompeii in 1814, and Humphry Davy was investigating the pigment by 1815.

Here is the part that gets me. Shine ordinary light on Egyptian blue and it glows back in the near infrared. Your eye cannot see it; a camera can. Conservators photograph objects that look unpainted and watch the blue light up where it has worn to nothing, and the same trick has found it on sixteenth-century paintings, including one by Raphael. In water it splits into nanosheets, so chemists are testing it for medical imaging and security inks. A five-thousand-year-old paint has a second career.

China built its own. Han purple and Han blue are barium copper silicates, the same crystal with barium swapped in for calcium, made in China from the Western Zhou period (1045 to 771 BC) until the Han dynasty fell around AD 220. Han purple colored the trousers of the Terracotta Army, buried in 210 to 209 BC. Pure, it is a dark indigo blue; the purple is red copper oxide from slow decay. In 2006 physicists found that in an exotic magnetic state it behaves as if it had lost a dimension.

Maya blue is not a mineral at all. It is indigo, the plant dye, locked inside a clay called palygorskite, and the clay makes it nearly indestructible: murals at Bonampak and Chichen Itza have kept their blue for a thousand years in a brutal climate. It was used from around 800 into the 1800s; then the recipe was lost until Constantino Reyes-Valerio published one in 1993. At Chichen Itza it was cooked beside the sacred sinkhole, and the people thrown into that sinkhole for the rain god had been painted with it.

Smalt is the sad one. It is cobalt glass ground to powder: cobalt oxide melted with quartz and potash, then crushed. European painters leaned on it from at least 1455 into the 1600s; Francis I bought a large quantity for his gallery at Fontainebleau in 1536. Fired under a glaze it keeps its color, which is why Ming porcelain and Delftware are still blue. In oil paint it slowly loses its color and goes gray. Cobalt blue does the same job without the heartbreak.

What can you buy? Genuine Egyptian blue, from a handful of makers who still fire it; it comes out coarse, weak and granular, and I like it anyway, the way I like a wobbly hand-thrown mug. My take: the first pigment humans ever made was a fake stone, and it is still teaching chemists tricks. Not bad for a substitute.

Pigment facts

These describe the pigment in general. Every brand's tube behaves a little differently, so test yours on scrap paper.

How to mix Egyptian blue

Genuine Egyptian blue is a mid blue with a faint green cast, so the nearest standard mix is cerulean blue with a touch of cobalt blue, about four to one, and a speck of white for the chalky look. What you cannot mix is the granulation; that only comes from the real coarse pigment.

Yellow ochre is the pairing that matters. Blue and ochre are the Egyptian palette, and the mix between them is a soft olive, close to the green the Egyptians got when a batch had too much lime.

Using Egyptian blue in watercolor

Use Egyptian blue where a sky needs to look like daytime. It is a clean, slightly greenish blue with none of ultramarine's evening mood, so it belongs in noon skies, shallow water and anything painted in full sun.

Its heavy granulation is the technique. Lay it wet into wet on rough paper, tilt the board once and leave it alone; the crystals drift into the hollows and dry as a speckled texture no smooth pigment can fake. Fuss with it and you lose that.

Pair it with the earths. Yellow ochre beside it looks warmer and the blue looks bluer, and a Venetian Red roofline under an Egyptian blue sky needs nothing else.

One thing I learned the hard way: because it lifts so easily, a glaze laid over a dry Egyptian blue wash picks it up and smears it into mud. Paint the blue last, or paint around it.

Egyptian blue vs Han blue (and Maya blue)

Han blue is Egyptian blue's twin with a different parent: barium in the crystal instead of calcium, fired hotter, with lead to help it along. Han blue's partner Han purple is really a dark indigo that only looks purple as it decays.

Then there is Maya blue, a different animal. There is no copper in it at all; it is indigo soaked into clay, and the clay is what makes it last. It is brighter and more turquoise than the two silicates, closer to #73C2FB than to #1034A6, and it survives acid that would strip most paints.

If Egyptian blue is the sky over the Nile at ten in the morning, Han blue is the same sky over the Yellow River, and Maya blue is a swimming pool in the Yucatan.

More color stories

Mel, founder of Tobio'sI make portable watercolor kits and I named the company after my cat. I write these pages for the beginner I used to be, one pigment at a time.