Plant dyes have been used for centuries to colour fabrics, papers, and even cosmetics, but behind their vibrant colour lies a fascinating world of chemistry. Plant-based dyes rely on a variety of compounds which are found in roots, leaves, fruits, flowers, and bark that produce a spectrum of hues. Unlike synthetic dyes, which are often created in a lab, plant dyes rely on organic molecules and these can vary and are based on the species, growing conditions, and extraction methods used. We need to understand the chemistry of plant dyes in order to be more efficient when natural dyeing and it is also as important to understand how they reveal their natural colour. We also need to look at what makes them unique, and how they can be effectively used in textile applications today.
The Science of Natural Colour: Pigments and Chromophores
The colours we see in plant dyes are the result of molecules known as pigments, they absorb certain wavelengths of light and reflect others. For plants, these pigments are located in specialised cells which can be extracted to dye fibres. The colour-producing part of these pigment molecules are called chromophore, which absorb visible light to reflect the colour seen by our eyes. Different plant pigments will reflect different colours which are based on their molecular structure and chromophores, which allow for a wide variety of colours to emerge from plants alone.
Primary Pigments in Plant Dyes
Several main pigment types are responsible for the colours found in plant-based dyes:
- Anthocyanins
Anthocyanins produce red, purple, and blue hues and are found in fruits, berries, and flowers like blueberries, red cabbage, and hibiscus. They are water-soluble and are sensitive to pH, which means they can change colour based on acidity or alkalinity. For example, anthocyanins can appear red in acidic solutions and blue in alkaline ones, and this makes them highly versatile but also challenging to fix in a particular hue. - Carotenoids
Found in carrots, marigolds, and saffron, carotenoids produce warm yellows, oranges, and red pigments, these pigments are fat-soluble and have a more stable structure compared to anthocyanins, making them less susceptible to pH changes but are also more prone to degradation from light and heat exposure. - Tannins
Tannins are found in many plants, including oak bark, tea leaves, and sumac. They produce a wide spectrum of earthy colours, ranging from soft yellows and warm browns to cool greys and deep blacks. These plants are naturally rich in polyphenols, which not only contribute to colour but also act as natural mordants, these compounds help dyes bond securely to fibres. Because of this, tannins are essential for creating durable, fade‑resistant colours in plant‑based dyeing. - Flavonoids
Flavonoids are responsible for pale yellows and other lighter hues found in plants like chamomile, weld, and onion skins. They’re known for their antioxidant properties, which protect plant cells from UV damage. In dyeing, flavonoids tend to produce soft colours that are more stable with the use of mordants. - Betalains
Betalains produce bright reds and purples, and are seen in beetroot. However, betalains are relatively unstable compared to other pigments. They fade quickly under sunlight and with washing. This quality makes them more challenging if we need to use them for long-lasting dyes but valuable for shorter-term or experimental projects.
The Role of Mordants
When natural dyeing, a mordant is usually required to bind dye molecules to natural fibres, and this process ensures that the colour adheres to the fibres and doesn’t wash out. Natural dyes often need mordants because plant pigments lack the chemical bonding properties of synthetic dyes. Common mordants include alum, iron, copper, and tannins. Each mordant can influence the final colour; for example, alum can enhance yellows, while iron can darken or “sadden” colours, giving them a muted, earthy tone.
Some plants, such as those high in tannins, act as natural mordants, which will allow for easier dyeing processes without additional chemicals. Tannin-rich plants like pomegranate rinds and sumac can produce more light-fast, wash-fast colours, making them essential in traditional plant dyeing.
Dye Extraction and Colour Development
The dye extraction process involves breaking down plant materials to release pigments. Most dyes are extracted using heat, where plant material is simmered in water to release the colour. Heat allows the pigment molecules to break free from the plant’s cellular structures, and then bond with water to create a dye bath. Extraction must be carefully managed because high heat can degrade certain pigments, especially anthocyanins and betalains.
To intensify or modify a colour, dyers often manipulate the pH of a dye bath by using acids like vinegar or bases like baking soda. For example:
- Anthocyanins shift from pink to purple to blue as pH changes.
- Turmeric, rich in curcumin, can shift from yellow to reddish-brown in different pH levels.
After the extraction process, the fabric is immersed in the dye bath. Some pigments bond directly to fibres, but others require repeated dips or prolonged soaking to achieve the desired saturation.
Lightfastness and Wash-fastness: Challenges with Natural Dyes
A critical challenge with natural dyes is ensuring the colour produced is able to resist fading over time. Light-fastness refers to how well a dye resists to fading when exposed to sunlight, wash-fastness measures its resistance to washing. Anthocyanins and betalains, are vibrant initially, they do have poor light-fastness and wash-fastness, limiting their use in applications requiring durability. Carotenoids and tannins, however, are relatively stable, particularly when paired with appropriate mordants.
Various traditional techniques help improve colour stability:
- Using tannin-rich mordants enhances the fastness of other plant dyes.
- Over-dyeing or layering colours from different dye baths can help create more complex, longer-lasting hues.
- Post-dyeing rinses with acidic or alkaline solutions help to set the colours more firmly into the fabric, particularly for pH-sensitive pigments like anthocyanins.
Environmental Benefits and Challenges
Plant dyes are generally more sustainable than synthetic dyes, which are derived from petro-chemicals and often require toxic additives. Natural dyes are biodegradable, and their waste products are far less harmful to waterways and soil. However, large-scale natural dyeing still poses challenges for example:
- High water use is often necessary for colour extraction and dye baths.
- Some mordants, particularly metal salts, can have environmental impacts if not disposed of properly.
- Sustainable sourcing of dye plants is essential to avoid over-harvesting, which can harm local ecosystems.
Many dyers today work to balance these challenges, using more sustainable mordants like alum and recycling dye baths to reduce water usage.
Future of Plant Dye Chemistry
With advancements in green chemistry there are researchers exploring methods to stabilise plant pigments improving the light-fastness and wash-fastness of natural dyes. Biotechnological approaches, such as microbial fermentation of plant pigments, could yield more consistent dye qualities while conserving the resources of plants. Additionally, ongoing research into sustainable mordants and plant–based tannins are helping to make natural dyeing even more sustainable.
For textile artists and hobbyists, understanding the chemistry of plant dyes offers an opportunity to experiment with a wide range of colours and techniques. and the process of creating with natural dyes is a journey through both history and science, blending tradition with innovation. Through careful experimentation and an understanding of each pigment’s chemical behaviour, dyeing with plants continues to evolve as a vibrant and sustainable art form.
Further Reading:
Core Chemistry of Natural Dyes
Negi, A. (2025). Natural Dyes and Pigments: Sustainable Applications and Future Scope. Sustainable Chemistry, 6(3), 23. (Covers anthocyanins, flavonoids, carotenoids, polyphenols, pigment stability, and sustainability.)DOI: MDPI
López‑Cruz, R., Sandoval‑Contreras, T., & Iñiguez‑Moreno, M. (2023). Plant Pigments: Classification, Extraction, and Challenge of Their Application in the Food Industry. Food and Bioprocess Technology, 16, 2725–2741. (Excellent overview of pigment classes (anthocyanins, carotenoids, betalains, flavonoids,) extraction methods, and stability issues). Springer,
Singh, S. Shyamkiran. (n.d.) Natural Dyes: Chemistry, Applications, and Sustainability. (n.d.) The Academic (General overview of natural dye chemistry and environmental considerations. A PDF Article.)
Pigment‑Specific References
Anthocyanins: Khoo, H. E., Azlan, A., Tang, S. T., & Lim, S. M. (2017). Anthocyanidins and anthocyanins: colored pigments as food, pharmaceutical ingredients, and the potential health benefits. Food & Nutrition Research, 61, 1361779. Food & Nutrition Research.net (Explains pH sensitivity and colour shifts.)
Carotenoids: Rodriguez‑Amaya, D. (2016). Natural food pigments and colorants. Science Direct (Discusses carotenoid stability, degradation, and extraction).
Betalains: Azeredo, H. M. C. (2009). Betalains: Properties, sources, applications, and stability. Journal Article Oxford Academic,
Notes: This article is widely cited for explaining betalain instability, including why beetroot dyes fade quickly under light, heat, and pH changes.
International Journal of Food Science & Technology, (Useful for explaining why beetroot dyes fade quickly.)
Published by the Institute of Food Science & Technology (IFST).
Hosted on Oxford Academic
Flavonoids: Grotewold, E. (2006). The genetics and biochemistry of floral pigments. PDF found here. (Covers flavonoid chemistry and UV‑protective roles.)
Tannins: Book: Haslam, E. (1989). Plant Polyphenols: Vegetable Tannins Revisited. (Cambridge University Press) Internet Archive (Classic reference on tannin chemistry and mordanting behaviour.)
Mordants & Fibre Bonding
Cardon, D. (2007): Natural Dyes: Sources, Tradition, Technology and Science. Archetype Publications. (A foundational text on mordants, tannin behaviour, and dye–fibre interactions.) Open Library
Bechtold, T., & Mussak, R. (2009). Handbook of Natural Colorants. Wiley. (Covers mordant chemistry, fibre bonding, and dye–substrate interactions.) Open Library
Extraction Methods & pH Manipulation
Chemat, F., Vian, M. A., & Cravotto, G. (2012). Green extraction of natural products: Concept and principles. International Journal of Molecular Sciences, 13(7), 8615–8627. MDPI (Explains heat extraction, degradation, and green extraction techniques.)
López‑Cruz, R., Sandoval‑Contreras, T., & Iñiguez‑Moreno, M. (2023). Plant pigments: Classification, extraction, and challenges of their application in the food industry. Food and Bioprocess Technology, 16, 2725–2741. Springer (Excellent for pigment extraction, pH effects, and stability.)
Lightfastness & Wash‑fastness
Bechtold, T., & Mussak, R. (2009). Handbook of Natural Colorants. Wiley. (Industry‑standard reference on fastness testing and pigment stability.) Open Library
Negi, A. (2025). Natural Dyes and Pigments: Sustainable Applications and Future Scope. Sustainable Chemistry, 6(3), 23. MDPI (Discusses photodegradation, pigment instability, and mordant effects.)
Sustainability & Environmental Impact
Shahid, M., & Mohammad, F. (2013). Perspectives for natural product based agents derived from industrial plants in textile applications. RSC Advances, 3(26), 12244–12287. Science Direct (Addresses environmental impacts, sustainable mordants, and dye‑plant sourcing.)
Siva, R. (2007). Status of natural dyes and dye‑yielding plants in India. Current Science, 92(7), 916–925. ResearchGate (Covers ecological considerations and sustainable harvesting.)
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