When working with natural dyes, one of the most important steps in the process is mordanting. Mordants are substances used to prepare fibers to better absorb and retain dyes, especially those derived from plants. Without a mordant, colors can appear dull or fade quickly after washing. Choosing the right mordant can significantly affect the final result in terms of both colorfastness and vibrancy. There are many different types of mordants available, both natural and synthetic, and the choice depends on the type of fiber, the dye being used, and the desired outcome. Understanding what to use as a mordant is essential for anyone interested in natural dyeing, whether you’re working with wool, cotton, silk, or other textiles.
Understanding the Role of Mordants
What Is a Mordant?
A mordant is a chemical or natural substance that helps bind the dye to the fiber. In natural dyeing, many plant-based dyes will not bond to fibers on their own. The mordant acts as a bridge between the dye and the fabric, improving the colorfastness and ensuring the dye doesn’t easily wash out or fade over time.
Why Use a Mordant?
Mordants serve several purposes in the dyeing process:
- Improve dye absorption
- Enhance color vibrancy
- Increase colorfastness (resistance to fading or bleeding)
- Modify the resulting color depending on the mordant used
Common Mordants Used in Natural Dyeing
Alum (Potassium Aluminum Sulfate)
Alum is one of the most popular mordants for natural dyeing, especially on protein fibers like wool and silk. It is relatively safe, easy to use, and does not significantly alter the color of the dye.
- Commonly used at 1015% of the weight of the fiber
- Often combined with cream of tartar to soften fibers and improve results
- Produces clear and bright colors
Iron (Ferrous Sulfate)
Iron mordant is known for darkening colors and shifting them toward grays, browns, and greens. It works well as a modifier in post-mordanting or as an after-bath treatment.
- Used sparingly typically 14% of the weight of the fiber
- Too much iron can damage delicate fibers like silk
- Enhances dull or earthy tones
Tannin
Tannins are naturally occurring compounds found in many plants. They are often used as a first mordant on cellulose fibers like cotton and linen, especially before applying metal mordants like alum or iron.
- Extracted from oak galls, sumac leaves, tea, or pomegranate rinds
- Improves bonding for dyes that struggle to adhere to cellulose fibers
- Often combined with alum for better results on plant-based fabrics
Copper (Copper Sulfate)
Copper mordants can produce cooler tones and increase lightfastness. However, copper is more toxic than alum or iron and should be used with caution.
- Can shift reds to purples and brighten blues
- Should be used with gloves and proper ventilation
- Not recommended for use with food-based dyes or children’s projects
Chrome (Potassium Dichromate)
Chrome is a very effective mordant that can yield brilliant and long-lasting colors. However, it is also highly toxic and environmentally harmful, and therefore it is not commonly used today outside of professional settings.
- Produces deep and rich shades
- Requires extreme caution and protective equipment
- Usually avoided in modern home dyeing due to safety concerns
Natural Mordant Alternatives
Homemade Tannin Sources
If commercial tannins are not available, you can make your own using common natural materials:
- Boiled tea leaves (especially black tea)
- Pomegranate peels or juice
- Acorns or oak bark
- Sumac leaves or berries
These materials are rich in tannins and can serve as a pre-treatment before applying other mordants like alum.
Salt and Vinegar Myth or Truth?
Many people believe that salt or vinegar can be used as a mordant. While they may help set some synthetic dyes, they are not true mordants for natural dyeing. Salt can help with dye uptake in some instances, and vinegar can adjust pH levels, but neither creates a permanent bond between fiber and natural dye on its own.
Choosing a Mordant for Different Fibers
Protein Fibers (Wool, Silk)
These fibers bond well with most mordants, particularly alum and iron. They are more delicate than cellulose fibers, so avoid harsh mordants like chrome or high concentrations of iron, which can cause brittleness or discoloration.
Cellulose Fibers (Cotton, Linen, Hemp)
Plant-based fibers are more challenging to mordant. Tannin followed by alum is the most common method. Sometimes an additional soda ash treatment is used to help fibers open up and absorb the mordant more effectively.
How to Apply Mordants
Mordanting Before Dyeing (Pre-Mordanting)
This is the most common method and involves soaking the fiber in a mordant bath before dyeing. It allows the mordant to penetrate the fibers thoroughly, leading to better results.
Mordanting During Dyeing (Meta-Mordanting)
In this method, the mordant is added to the dye bath itself. While convenient, it may produce less consistent or weaker results depending on the dye and fiber used.
Mordanting After Dyeing (Post-Mordanting)
This technique involves soaking the dyed fiber in a mordant bath. It is often used with iron to darken or shift the original color. Caution is needed to avoid damaging the fiber or changing the color too drastically.
Environmental and Safety Considerations
Disposal of Mordant Solutions
Some mordants, especially metal-based ones, can be harmful to the environment. Avoid pouring mordant solutions down the drain. Instead, dispose of them responsibly according to local regulations or neutralize them with safe substances like baking soda before disposal.
Personal Safety Tips
- Always wear gloves when handling mordants
- Work in a well-ventilated area or outdoors
- Label all containers clearly
- Keep mordants away from children and pets
Knowing what to use as a mordant is fundamental to successful natural dyeing. Each mordant interacts differently with various fibers and dyes, offering a range of colors and effects. Whether using safe and accessible options like alum and tannins or exploring deeper color shifts with iron or copper, selecting the right mordant can transform your dyeing results. With care, experimentation, and respect for safety, you can achieve stunning, long-lasting colors in your textile projects. By understanding and using mordants correctly, natural dyeing becomes not only more vibrant but also more rewarding.