Turnsole
A medieval dye from Chrozophora tinctoria, shifting from blue to red with acidity
No single value: Turnsole is a material, and its colour varies. The background shows its family, purple and violet.
Turnsole is a dye made from the fruit of Chrozophora tinctoria, used in medieval manuscripts and as a food colourant. Its colour changes from blue to purple or red depending on acidity, and it was often a substitute for pricier dyes like Tyrian purple. Once common in illuminators’ palettes, it faded from use after the seventeenth century.
- Made from the fruit of Chrozophora tinctoria
- Colour shifts from blue to red with acidity
- Used in medieval manuscript illumination
- Also used as a food dye and for cheese rinds
- Fell out of use after the seventeenth century
What colour is Turnsole?
Turnsole is a dye that produces translucent colours ranging from blue to purple to red, depending on how acidic or alkaline its environment is. It is made from the fruit of the Chrozophora tinctoria plant. The dye is known for its ability to shift colour, a property later used in chemical tests like litmus. Its shades are less intense than those of mineral blues like lapis lazuli.
Where does Turnsole come from?
The name 'folium' means 'leaf' in Latin, but the dye actually comes from the fruit of Chrozophora tinctoria. The technique for extracting turnsole was developed in the thirteenth century, making it a staple for manuscript illuminators. It was valued as a cheaper alternative to Tyrian purple and was used widely until mineral blue pigments became more available and reliable.
How is Turnsole made?
To make turnsole, the unbroken fruits of Chrozophora tinctoria are collected in late summer or early autumn. The dye was often sold on linen pieces, which could be soaked to extract the colour. The process sometimes involved storing the dyed textiles in damp cellars with pans of urine, which produced ammonia and affected the final colour. The main colouring compound is chrozophoridine.
Where Turnsole is used
Turnsole was a key dye for medieval manuscript painting, especially for glazes and shading. It was also used to colour food, such as by steeping it in milk or adding it to water for recipes. In the Netherlands, it was used to dye the rind of cheese red. Its use in textiles and art declined after more stable mineral pigments became common.
Purple around the world
What the purple and violet family means from country to country.
In Holy Week, members of religious brotherhoods walk in procession in robes and pointed hoods, many of them purple, the colour of penance. A purple band also marked the flag of the Second Republic.
Sacred and holyPolitics and protestSource: Holy Week in SpainSuffragettes campaigning for women's votes wore purple, white and green: purple for dignity, white for purity and green for hope.
Politics and protestCourageSource: SuffragetteA child born to a reigning Byzantine emperor was called porphyrogennetos, born in the purple. The birth took place in a palace room lined with purple stone.
Royalty and powerAweSource: Born in the purpleIn the elections of 2005, voters dipped a finger in purple ink to prevent double voting. The stained finger, held up for cameras, became a sign of the vote.
Politics and protestPrideSource: Election inkPurple dye from the murasaki plant was costly and hard to make. In the court rank system set up under Prince Shotoku, the highest officials wore purple caps.
Royalty and powerAweSource: Twelve Level Cap and Rank SystemThe Phoenician cities of Tyre and Sidon made Tyrian purple from sea snails. The dye was so costly that it became the colour of kings and Roman emperors.
Royalty and powerAweSource: Tyrian purpleShades and relatives of Turnsole
Turnsole’s colour can range from blue through purple to red, depending on the acidity or alkalinity of its surroundings. It was sometimes confused with other plant-based blues like woad and indigo, but its shifting colour and translucency set it apart. The dye is also known as katasol and folium.
Questions people ask about Turnsole
What colour is turnsole?
Turnsole can appear blue, purple, or red, depending on how acidic or alkaline its environment is. This shifting quality made it useful for both art and food colouring.
Where does the name turnsole come from?
The dye is also called folium, which means 'leaf' in Latin, but it is actually made from the fruit of the Chrozophora tinctoria plant.
What was turnsole used for?
Turnsole was used mainly in medieval manuscript painting, as well as for colouring food and dyeing cheese rinds, especially in the Netherlands.
How was turnsole made?
The dye was extracted from the unbroken fruits of Chrozophora tinctoria, often by soaking linen in the dye and using ammonia from decomposing urine to affect the colour.
Good reading and sources
The facts on this page come from the Wikipedia article "Turnsole", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). Rang rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes. The swatch is an approximation: named colours are not fixed standards, and every screen shows them a little differently. If something is wrong, tell us. Last refreshed 2026-10-03.
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