Did you know that Mimosa hostilis can be used as a textile dye? Extracts from its bark give fabrics yellow to ochre and even reddish colours. The results are unique and unrepeatable and depend on the concentration and type of textiles used.
The use of natural products to dye textiles is ancestral. In a cave in Georgia, traces of blue, grey and pink dyed linen were found that date back 30,000 to 36,000 years, when the first humans left the African continent and began to populate Asia and Europe1. The decoration and colouring of our clothes has had a long evolution, until reaching industrial and chemical uses.
"There is a joke in China that you can tell the fashionable colour of the season by the colour of its rivers", is popularly said among environmental activists who criticise the excessive use of chemicals in the fast-fashion industry2. Concern about the environmental and human health damage caused by chemical dyes has led to a new surge in natural dyes in recent decades3.
But the greatest value of dyeing with natural products is the uniqueness of each colour, since you never get the same one - the possibilities are endless!
"Because the nature of the colour and the materials you use can vary, the colours or shades you eventually get will be modified. That's really the value of dyeing with natural dyes", says Dr Ana Lilia Vigueras, a biologist who is an expert in natural dyes at the University of Guadalajara, a centre of studies in western Mexico.
The results are unique and unrepeatable because they influence everything from the concentration of the natural dye used, the type of fibre to be dyed and even the water used, since its chemical composition can vary from one region to another, according to Vigueras.
Textile dyeing plants
Nature offers a vast number of choices of plants, animals and minerals from which dyes can be obtained. Some well-known dye plants are indigo (blue), Palo Brasil (red), achiote (red-orange) and Palo Campeche4 (brown-black). The bark of Mimosa hostilis (Mimosa tenuiflora, jurema or tepezcohuite) generates ochre or reddish tones and is used for dyeing fabrics and furs5.
Mimosa hostilis has a high content of tannin6, a chemical and astringent plant component7 present in the roots, bark, leaves, shoots, floral parts, wood, or seeds of various plants8 and can be used as a dye9.
Plants produce a wide variety of tannins, resulting in an unlimited number of different chemical profiles in different plant organs10. Due to their chemical composition, tannins are capable of precipitating proteins, enzymes, carbohydrates and alkaloids; they have been used historically to tan animal skins and may have antimicrobial, antifungal or antiviral properties, among others11.
The dried and ground bark of Mimosa hostilis has the appearance of a fine red to brown powder12. However, when used as a dye, its colouring can range from yellow to brown13 on cotton fibres, depending on the amount used and the products used to fix the dye (called mordants).
The yellow coloration may be due to the fact that Mimosa hostilis contains flavonoids14, which are components of the plants that contribute to its coloration15. Many fruits and vegetables owe their colour to the presence of flavonoid pigments16, whose colour range from white/cream to red/blue, with a greater presence of yellows17.
However, colouring can result in other shades depending on the type of fibre, the concentration of the product or the combination with other colourings18. The fibres can be artificial, such as polyester, or natural, including animal and vegetable fibres19.
Some animal fibres are silk, wool, cashmere, angora and alpaca. Among the fibres of vegetable origin are cotton, linen, ixtle and sisal20.
Use as a colour fixer (mordants)
Thanks to its high content of tannins, Mimosa hostilis can also be used as a natural colour fixative, which is called a mordant.
A mordant is a chemical that aids in the absorption and fixation of dyes and prevents the discoloration of fibres21, a common problem with some natural dyes. Tannins, or tannic acid, are a type of natural mordant22.
The use of tannins as mordants has several advantages: tannins reinforce the coloration of vegetable dyes with yellow, orange, red and violet dyes; the dyed fibres have good resistance to washing and light; and, in addition, they are indispensable for the dyeing of vegetable fibres such as cotton and linen23.
In the Multi-functional effects of textiles dyed with madder roots poder (Rubiatinctoria) study, which evaluated the effects of two natural mordants and one natural dye, tannins from Mimosa (a genus to which Mimosa hostilis belongs) were used as a mordant to dye a cotton fabric with Rubia tinctorum24. The result was a greater concentration of colour in fabrics previously mordanted with Mimosa tannins than in those bitten with alum, a very common natural dye.
However, the study warns that a high concentration of tannins may also prevent the absorption of the dye25.
Experiments with Mimosa hostilis
Although the process of dyeing with natural dyes is handmade, experiments are beginning to be done to use Mimosa hostilis for industrial fibre dyeing26.
In the study Dyeing of white and indigo dyed cotton fabrics with Mimosa tenuiflora extract, extract of Mimosa hostilis was used to understand the effect of different mordants on a white cotton fabric ready for dyeing and on another indigo dyed fabric.
What was obtained were various colour effects by the action of Mimosa hostilis, ranging from blue-green tones to shades of yellow and red, and which varied depending on the mordants used27.
This study highlighted the growing importance of natural dyes in the textile industry because they are biodegradable and sustainable; furthermore, its potential in the blue denim dyeing process was highlighted28.
How to dye textiles with vegetable dyes?
Unlike synthetic dyes, which use toxic products and metals that can damage the body, either by causing allergies on the skin or by the risk of toxic waste they generate, natural dyes do not represent a health risk, their use is not restricted and they have the quality of being unique.
And just as there is no single result, there is no single process for dyeing with natural dyes.
However, there are some guidelines and recommendations that Vigueras and her colleague Liberato Portillo have documented29 that can be a guide for those interested in dyeing textiles with Mimosa hostilis:
How to dye textiles with Mimosa hostilis
• The fibres to be dyed must be free of impurities so that they retain the dye better.
• The fibre to be dyed must be moistened before starting the mordanting process. It is also recommended that the fabric be wetted before dyeing.
• The fixing process can be done before or after the dyeing and usually involves adding the mordant in hot water along with the fibre.
• If this is done before the dyeing, the fibre is placed in a container with warm water that contains enough mordant to cover it. It is left to heat to boiling point for 30 to 60 minutes, moving constantly. In the case of fibres such as cotton or ixtle, it requires between 1 and 3 days.
• If the mordanting is done after the dyeing, the dyed garment is placed in a container with warm water containing the colour fixative.
There are several methods for dyeing with natural dyes:
• Live dyeing: this is the simplest way, as it consists of introducing the un-mordated fibre directly into a water bath with the dye.
• Dyeing with plants: the plant must be perfectly soaked with hot water in a container where the fibre to be dyed will be introduced. In general, 100% of the plant is used (whether branches, leaves, flowers, bark, etc.) which must equal the weight of the wetted fibre. The minimum approximate time for dyeing is 30 minutes, during which the mixture must be stirred to favour the homogeneous diffusion of the dye in the textiles. Subsequently, the fabric is washed.
• Cold dyeing: for this technique, plants that provide tannins must be used, which, in addition to providing fixation, provide a certain amount of colour. The dyes used in this technique have an acid base (some fruit tree barks, hard woods, some fruits, ferruginous soil, among others).
Always take note!
A final recommendation is to make notes to have a record of the process by which a certain colour was achieved and take a sample or a photograph of the dyed fibre, in case you want to replicate it, knowing that you may not be able to match the colour.
Follow these recommendations and enjoy the experience of making your own dyes using Mimosa hostilis - share your results with us!
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26. Erkan, G., et al. (2014)
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29. Vigueras, A.L. et al (2016)