Natural pigments and dyes
Dyeing with natural dyes is a process in which plant, animal, or mineral pigments are used to color fabrics. Unlike synthetic dyes, natural dyes require preliminary fiber preparation and special treatment to achieve lasting results.
NATURAL DYEING MANUAL
Basic Dyeing Supplies:
The following items are needed for natural dyeing:
- natural fiber fabrics,
- pots of various sizes, strainers, hot plates,
- baking soda and washing soda,
- aluminum sulfate (alum) and iron sulfate,
- dye source (plants, fruits, peels...),
- scale.
Fabric Selection
Synthetic fibers, such as polyester, are hydrophobic and therefore unsuitable for natural dyeing. Only natural fibers are used, which are divided into two main groups:
- Cellulose fibers: Plant-based (e.g., cotton, linen, denim), composed of cellulose,
- Protein fibers: Animal-based (e.g., wool, silk), composed of proteins (keratin).
Protein fibers bind natural dyes more effectively, therefore they usually achieve more intense colors. Cellulose fibers, however, require more complex preparation processes (mordanting).
Note: Protein fibers are sensitive to heat; boiling them for too long can cause shrinkage or felting.
Fabric swatches measuring 15 × 15 cm made of silk, wool, linen, cotton, and denim are often used for dye testing.
WOF (Weight of Fibres)
The weight of fibers (WOF) is the fundamental unit of measurement in the dyeing process. All ingredients and chemicals are measured relative to the weight of the fabric.
- Example: 1 kg of fabric = 100 g of washing soda (10% WOF).
Fiber Cleaning
Before dyeing, fabrics must be cleaned of fats, waxes, and dirt. The process varies depending on the type of fiber:
- Cellulose fibers: Clean with washing soda (10% WOF). Boil the fabric for one hour in water with soda. Dissolve the washing soda in enough water to completely cover the textile. Bring the water with the textile to a boil and simmer for approximately one hour.
- Protein fibers: Clean with baking soda (1 tablespoon per 1 liter of water). Soak for 30 minutes.
After cleaning, rinse the fabric in lukewarm water and either dry it or proceed immediately with mordanting.
Mordanting
Mordanting is the pre-treatment of fabrics to improve dye binding and achieve colorfastness. Mineral salts (alum, iron), plant tannins, and soymilk are used.
Tannin Bath
Used primarily for cellulose fibers (e.g., cotton, linen).
- Dosage: 10% WOF of tannin.
- Dissolve the tannin in hot water, then mix it into lukewarm water. Use a large container and ensure the textile is fully submerged in the bath.
- Soaking: Overnight in a lukewarm bath, followed by rinsing.
Note: We used pure tannin (https://www.revivo.si/tanin_vodotopen_500g), which was quite dark and significantly affected the color of the textile. We recommend using a lighter-colored tannin or soaking in the bath for a shorter time (e.g., 30 minutes).
Alum and Iron
- Alum (aluminum sulfate): 10% WOF, produces lighter tones.
- Iron sulfate: 2% WOF, produces darker tones.
Weigh the alum or iron sulfate and dissolve it in a bath of lukewarm water, then add the textile. We decided to let the fabric soak overnight. This step doesn't need to be that long; successful results can also be achieved by soaking the fabric in the bath for 1-2 hours. However, in natural dyeing, the principle generally applies that the longer the material soaks, the more lasting the results one can expect. It is ideal to stir the textile during soaking for more even color.
Warning: For both processes, it is worth mentioning that we ensured proper protection when handling the textiles. Although these are not toxic substances, wearing gloves is still advisable, as some individuals may experience an allergic reaction. If contact with skin occurs, rinse the affected area with water.
Soy Milk
Used exclusively for cellulose fibers, as it creates a protein layer.
- Ratio: 1 part soy milk : 4 parts water.
- Process: Soak for 15 min, wring out, dry; repeat the process 3 times. The fabric needs a few days to rest and 'mature'.
Preparation of Dye Baths
Preparing the dye baths is the final step of the wet process. The rule here is: the more raw material we have, the more colored the bath will be. This also means, of course, that our final fabric will be more pigmented than otherwise. Still, as a guideline for a good ratio, we have the weight of the fabric, which should be equal to the weight of the raw material used to prepare the dye bath: equal weight of raw material and fabric (1 : 1).
Process:
- Weigh the fabric and the raw material.
- Boil the raw material in water until the desired intensity is reached.
- Submerge the fabric in the lukewarm dye bath (it's best if the fabric floats freely in the bath).
- Let the fabric soak for 2 hours to overnight.
- Rinse in lukewarm water and dry away from sunlight.
The results of dyeing depend on numerous factors (type of fabric, amount of pigment, pH, soaking time).
Fabric Dyeing
The dyeing process itself follows these steps:
- Fabric Preparation – Dampen the dry fabric or use already washed fabric, depending on the fixation process (whether it was dried or not).
- Immersion in the Bath – Completely submerge the fabric in the dye bath. Squeeze out air from the fabric (air bubbles can cause uneven dyeing).
- Stirring – Gentle stirring is recommended to distribute the pigment evenly and prevent pooling in folds.
- Soaking – Leave the fabric in the dye bath for at least 2 hours or overnight; longer times result in more intense color.
- Finishing – After dyeing, rinse the fabric with lukewarm water, dry at room temperature, and away from sunlight.
Influence of Factors
Dyeing results can vary even with identical procedures. The final color is influenced by:
- Type and density of the textile,
- Amount of raw material used,
- Type of fiber and its ability to bind pigments,
- pH of the bath,
- Soaking time,
- Method of stirring,
- Method and duration of drying and storage.
For example, red cabbage can yield blue tones one time and purple tones another, depending on the conditions.
The Influence of pH on Colors
Adjusting the pH of the dye bath allows for obtaining different color shades:
- Acidic bath (vinegar): Colors become lighter or change shade (e.g., green → pink),
- Basic bath (baking soda): Colors become more intense.
In the process of creating and developing colors, we use baking soda to create a basic bath and vinegar to create an acidic one. Vinegar often changes colors to lighter shades or even completely different ones from those originally obtained. For instance – a green dye bath from meadowsweet changes to a pink color with a drop of added vinegar. Adding baking soda, on the other hand, often saturates the dye bath more, resulting in stronger colors than we would otherwise get. The quantity used of both additives is arbitrary, and the reaction is immediate.
Shibori Technique
Shibori is a Japanese technique of tying, stitching, or pleating fabric before dyeing, which creates patterns. It is often used in combination with natural dyes (e.g., golden onion skin dye bath).
Color Groups
Based on the raw materials, we divided the dye baths into 4 color groups:
- Yellow: Meadow clover, marigold, turmeric, golden onion, wood fungus.
- Red: Pelargonium, common poppy, pomegranate peel, avocado peel, avocado pits, red onion.
- Blue: Red cabbage, black beans, aronia, combined dye baths.
- Green: Meadowsweet, mint, carrot tops, birch leaves, combined dye baths.
Isolating Pigments from Dye Baths
In addition to dyeing fabrics, dry powdered pigments can be obtained from used dye baths. These are useful for printing pastes, dyeing biomaterials, and other artistic or textile applications.
Required Ingredients and Tools
- approximately 500 ml of dye bath,
- 18 g of alum (aluminum sulfate),
- 8 g of baking soda,
- a container with enough space,
- a filter (e.g., laboratory paper or dense fabric),
- a spoon for stirring.
Procedure
1. Adding to the Dye Bath
- Slowly pour the alum solution into the container with the dye bath while stirring.
- Then, while stirring continuously, slowly add the baking soda solution.
2. Reaction
- A chemical reaction occurs when the two solutions come into contact: the liquid begins to foam, and a precipitate (pigment) forms in the bath.
- Stir for at least 2 minutes during the reaction so that the pigments bind with the salt in the water.
3. Phase Separation
- Wait for the liquid to separate into two layers: the upper (liquid) layer and the lower (thick, containing pigment) layer.
- Carefully decant the upper layer.
4. Filtering
- Pour the lower layer containing the pigment through a filter.
- Leave the pigment on the filter to dry completely.
5. Grinding
- Crush the dried pigment into a fine powder. This yields the dye in dry form.
Using Pigments
- The pigment can be mixed with various binders (natural or synthetic).
- In practice, pigments are often added to screen printing paste, which is then used to print on cotton or other fabrics.
- Pigments are also useful for dyeing biomaterials (e.g., a combination of sawdust and alginate).
Author: Green Lab (Center Rog), Textile Lab (Center Rog), year: 2025.
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. More information: CC-BY-NC 4.0