You may not be aware, but the debate over synthetic vs natural dyes has been raging since the mid-1800s. At first, the issue was cost. And then, as the state of medical science advanced and began linking synthetic dyes to cancer, the debate shifted to safety. Early synthetic dyes were made from coal tar. Today, synthetic dyes are considered to be safer than they were in the past despite being often designed from naphthalene, but are still a major source of pollution. However, they are cheaper to purchase than their natural counterparts and they are more effective, longer-lasting, and are currently cheaper to manufacture.
Being inexpensive doesn’t necessarily mean they are the best choice for the future to the exclusion of natural dyes (a practice which seems to be standard in the textile industry currently), however. So what if the natural dyes cost more so long as they don’t poison our environment!
Plants were once the principal source for most dyes used. However, their use has dropped off significantly, resulting in a loss of valuable knowledge and techniques. Recovering this information would be of great benefit to the dye industry and the world today.
In Southern Italy, a group of researchers took on the task of surveying, cataloging, and analyzing the dyeing plants used in the region.  Their purpose was to help recover the fading or lost knowledge and techniques of generating plant-derived dyes.
The catalog, complied from archival, ethnobotanical, and iconographic works of the region, contains 440 species of flowering plants, all but 18 of which have been historically used for dyes, and 72 mushroom and lichen specimens, two of which were not used for dyeing. Some of the plants discussed include dyer’s woad, pomegranate, English walnut, flax-leaved daphne, turmeric, rose madder, and elder. Dye was extracted from each specimen and the data recorded, noting the percentages of color extracted from each part of the specimen plant, i.e., stem, leaf, root.
Interestingly, the dominant colors able to be extracted from the plants were as follows: 54% yellow, 17% red, 13% green, 6% brown, 4% blue, 3% black, gray 2%, and purple 1% (Figure 1). The authors report that the dominance of yellow was not surprising because “[t]he range of colors that starts from yellow and turns towards red (the second most represented color) is in fact obtained mainly from the variety of tannins present in plants in large quantities.” Stems and leaves are high in tannins and are the parts of the plants often associated with dyes. Red and yellow were also the two most common colors extracted from mushrooms and lichen. (Figure 2)
Figure 1: The different color breakdowns in plant families reported in the flora of dye plants. At the center of the graph are the percentages of the extracted colors in total. Image taken from Prigioniero A, Geraci A, Schicchi R, Tartaglia MC, Zuzolo D, et al. Ethnobotany of dye plants in Southern Italy, Mediterranean Basin: floristic catalog and two centuries of analysis of traditional botanical knowledge heritage. Journal of Ethnobiology and Ethnomedicine. 2020;16:31, open access.
Figure 2: Total percentages relative to the colors taken from fungi and lichens. Image taken from Prigioniero A, Geraci A, Schicchi R, Tartaglia MC, Zuzolo D, et al. Ethnobotany of dye plants in Southern Italy, Mediterranean Basin: floristic catalog and two centuries of analysis of traditional botanical knowledge heritage. Journal of Ethnobiology and Ethnomedicine. 2020;16:31, open access.
Of the 440 species of flowering plants, researchers were able to find 283 in the field, speculating that a decrease in the number of species of plants may be due to lack of need of plant dyes as synthetics became popular over the past two centuries. The researchers also considered environmental changes to be a possible factor in the decrease in plant species.
The researchers hope their catalog of hundreds of pigments and colors and their categorized sources will provide a basis for a recovery of an eco-sustainable and economically sustainable natural plant dye industry, starting in Southern Italy, which would not only impact the dye industry but the environment as well. And with increasing interest in natural dyes as well as sustainable extraction technologies, there is a surmounting opportunity here to reverse decades worth of environmental pollution.
Reference Prigioniero A, Geraci A, Schicchi R, Tartaglia MC, Zuzolo D, et al. Ethnobotany of dye plants in Southern Italy, Mediterranean Basin: floristic catalog and two centuries of analysis of traditional botanical knowledge heritage. Journal of Ethnobiology and Ethnomedicine. 2020;16:31. [journal impact factor = 3.007; times cited = 4]
Image Source: https://upload.wikimedia.org/wikipedia/commons/b/bd/NATURAL_DYES.jpg