Crystal violet
A synthetic purple dye used in science, medicine, and industry
No single value: Crystal violet is a material, and its colour varies. The background shows its family, purple and violet.
Crystal violet is a synthetic dye with a deep blue-purple colour, widely used in laboratories and industry. Known as gentian violet, it has served as a stain for cells and bacteria, a textile dye, and a topical antiseptic, though its medical use has declined due to safety concerns.
- Crystal violet is a key stain in Gram's method for bacteria.
- Its colour changes with pH, from yellow to green to purple.
- It was once widely used as a topical antiseptic.
- Crystal violet is used to dye textiles and inks.
- It can be toxic and is considered carcinogenic in some countries.
What colour is Crystal violet?
Crystal violet is a man-made dye that produces a strong blue-violet colour in water. Its shade changes with acidity: it appears yellow in very acidic solutions, green in mildly acidic ones, and purple at neutral pH. The dye is known for its ability to stain cells and bacteria, making them easier to see under a microscope. It is not related to the gentian or violet flowers, though its colour is similar to their petals.
Where does Crystal violet come from?
The dye was first made in 1883 by Alfred Kern in Basel, Switzerland, as part of research into synthetic dyes. Its alternative name, gentian violet, was introduced by Georg Grübler in Germany for use in biological staining. Early on, the name covered a mix of similar dyes, but over time it became linked to crystal violet itself. The colour's name refers to its resemblance to certain flower petals, not to its ingredients.
How is Crystal violet made?
Crystal violet is produced through chemical reactions involving dimethylaniline and other reagents. One process forms a colourless compound, which is then oxidised to create the vivid dye. The final product is a salt, combining a coloured organic ion with chloride. The dye’s colour can shift depending on the acidity of its environment, and it can even become colourless under certain conditions.
Where Crystal violet is used
This dye has many uses. In science, it is a key stain for viewing cells and bacteria, especially in Gram staining. It is also used to mark skin for surgery and piercings, and to treat some fungal infections. In industry, it colours textiles, paper, inks, and even products like antifreeze and detergents. Crystal violet is also used in DNA and protein staining for laboratory research, and was once common in duplicating machines.
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 Crystal violet
Crystal violet is part of the methyl violet family, which includes dyes with fewer methyl groups. Its colour can vary from yellow to green to purple, depending on the acidity of the solution. The name gentian violet was once used for mixtures of related dyes, but now usually means crystal violet.
Questions people ask about Crystal violet
What colour is crystal violet?
Crystal violet is a strong blue-violet dye. Its shade can shift to green or yellow depending on how acidic the solution is.
Where does the name 'gentian violet' come from?
The name refers to the dye's resemblance to the colour of some gentian flower petals. It is not made from gentians or violets.
What is crystal violet used for?
It is used to stain cells and bacteria in laboratories, mark skin in medicine, dye textiles and paper, and colour inks. It has also been used as an antiseptic.
How is crystal violet made?
It is made by reacting chemicals such as dimethylaniline and formaldehyde, followed by oxidation, to produce the coloured dye.
Is crystal violet safe?
Crystal violet can be toxic and has been found to cause cancer in animal studies. Its use on the body is restricted or banned in some countries.
Good reading and sources
- Crystal violet on WikipediaEncyclopedia
- More pictures on Wikimedia CommonsPictures
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Crystal violet", 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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