The Blue That Cost as Much as Gold

In Renaissance painting contracts, one colour got written up like a precious material: ultramarine, made from a stone mined in what is now Afghanistan. The odd part is that crushing the stone doesn't give you that blue. Getting it out took a strange kneading ritual in wax, resin and lye.

Walk into any big gallery of European paintings and you'll find her quickly. The Virgin Mary, in a robe of deep, glowing blue. It's such a familiar sight that it's easy to look straight past it.

But that blue was more than a colour choice. Mary's robes were often painted in a rich ultramarine, and ultramarine was the most expensive pigment ever to be widely used. When the robe went on, someone was paying for it, and the paperwork shows they knew exactly what they were paying for.

Take a contract from Florence in 1485, for an altarpiece of the Adoration of the Magi. The painter is to colour the panel at his own expense with good colours, and with powdered gold on the ornaments that call for it. Then the blue. It must be ultramarine, the contract says, "of the value of about four florins the ounce."

Think about that for a second. Not "use a nice blue." A named pigment, with its price per ounce written into the agreement, sitting right next to the gold.

From beyond the sea

The name gives away where it came from. Ultramarine comes from the medieval Latin ultramarinus, meaning "beyond the sea", because it had to be imported into Europe.

It was made from lapis lazuli, a semi-precious stone mined in what is now Afghanistan, near a place called Sar-i-Sang. For centuries that was almost the only source Europe had. The mines were hard to reach, and for much of the year they were largely cut off. Italian traders were bringing it in during the fourteenth and fifteenth centuries, and in the early modern period Venice became central to both making the pigment and distributing it.

So by the time a painter in Florence opened a little packet of blue, that stone had come a very long way.

The disappointing grey

Here's the twist. You'd assume that if you have a gorgeous blue stone, you just grind it up and you've got gorgeous blue paint.

You don't. The early method was simple washing and grinding, and what it gave you was a pale, greyish blue. Rather a let-down, given the price of the rock. The intense blue particles are mixed in with other material in the stone, and grinding alone doesn't separate them.

So the problem wasn't making the stone into powder. It was getting the blue out of the powder.

Kneading out the blue

The solution, as described by the painter Cennino Cennini, sounds more like baking than chemistry.

You take finely ground stone and mix it into a sort of dough with melted wax, resins and oils. You wrap that dough in cloth. Then you put it in a bowl of weak lye, an alkaline solution, and knead it.

As you work it, the blue particles come out into the liquid, and the rest stays behind in the sticky lump. It's a bit like panning for gold, except you're squeezing the treasure out of the dirt rather than washing the dirt away from the treasure.

And here's the elegant part. The process was repeated at least three times, and the blue didn't all come out at once. The most intense particles came out first. Each kneading after that gave a lower grade. The very last one gave a pale grey pigment called ultramarine ash, which was prized in its own right as a glaze (a thin, see-through top layer of paint) for its pale, transparent blue. Every grade got used.

So one lump of stone gave you not one product, but a whole price list, from the finest blue down to the ash.

The money

That first, richest grade is where the legend comes from. The very best grades could be worth more than gold. There are records of even the raw stone costing as much as gold in the fifteenth and sixteenth centuries.

For a more down-to-earth comparison, look at the other blue painters had to hand: azurite, a copper mineral. In mid-fifteenth-century Florence, a period with good records, high-grade ultramarine cost ten to fifteen times as much as azurite.

That price shaped how paintings were organised, and how they were made.

On the business side, ultramarine in early Renaissance contracts was often supplied specially by the patron and treated as a separate payment. Patrons would often pay for the exact amount of ultramarine they wanted in the picture. Skilled negotiators made sure the patron was the one covering it, since it could cost far more than all the other colours combined. It's the Renaissance equivalent of a builder's quote with one line that says "marble: client to supply".

On the studio side, painters learned to make a little go a long way. One trick was to lay down cheaper blues first, azurite, smalt (a ground blue glass) or indigo (a plant dye), and then put ultramarine on top only as a thin final glaze. The expensive stuff did the job of being seen. The cheap stuff did the job of filling the space underneath.

The prize that killed the price

Right up to the 1820s, then, the finest blue in painting was a luxury good. What changed that was a competition.

In 1824 a French society offered a prize of 6,000 francs to anyone who could produce ultramarine artificially, at an affordable price. Within a few years there were workable recipes. Jean Baptiste Guimet devised one in 1826 and claimed the prize in 1828; Christian Gmelin came up with another in 1828. Guimet kept his method secret. Gmelin published his.

The synthetic version was a different world on price. French ultramarine cost about a hundred times less than the real mineral. Mass production followed, and by 1851 it was cheap enough to be used as laundry blueing, the stuff added to the wash to make whites look whiter.

From the Virgin's robe to the laundry tub in a few decades. It's quite a fall.

Not quite a law of nature

One honest caveat. "Worth more than gold" makes a great headline, but it isn't a fixed rule. It's true of the very best grades, and true of some records. Ultramarine came in grades, from the finest blue to the greyish ash, and prices varied with them. What the records do show is that high-grade ultramarine was extraordinarily expensive, ten to fifteen times the price of azurite in mid-fifteenth-century Florence, and treated in contracts with the kind of care you'd give to a precious material.

A robe that's also a receipt

So the next time you're standing in front of one of those altarpieces, look at the blue again.

It's a colour, yes. But it's also a price tag. Somebody paid for that robe, very possibly by the ounce, and wanted the world to know that they could. That glowing blue is a stone carried all the way from Afghanistan, kneaded out of wax and lye, laid on thinly over a cheaper base, and itemised in the contract right alongside the gold.

SOURCES

1. The National Gallery, London, "Colour Stories: Blue." https://www.nationalgallery.org.uk/podcast/colour-stories-blue (accessed 25 Oct 2026)

2. C. Hoeniger, "The Identification of Blue Pigments in Early Sienese Paintings by Color Infrared Photography," Journal of the American Institute for Conservation 30, no. 2 (1991), article 1. https://cool.culturalheritage.org/jaic/articles/jaic30-02-001_1.html (accessed 25 Oct 2026)

3. Chrysler Museum of Art, "The History of Art in Color: Blue." https://chrysler.org/the-history-of-art-in-color-blue/ (accessed 25 Oct 2026)

4. Wikipedia, "Ultramarine." https://en.wikipedia.org/wiki/Ultramarine (accessed 25 Oct 2026)

5. SUNY Oneonta, "Artist contracts" (translated Renaissance contract texts, including Ghirlandaio's 1485 contract). https://www.oneonta.edu/faculty/farberas/arth/arth200/artist/artist_contracts.htm (accessed 25 Oct 2026)