Natural dyeing has seen a resurgence in popularity, as it brings beautiful colours and sustainable practices to the world of fibre arts. When dyeing delicate fibres like merino wool and silk, the process requires careful preparation to ensure vibrant, long-lasting colours. This preparation step is known as mordanting, which is a vital process that prepares fibre to effectively bind with natural dyes. Here, we’ll cover the essentials of mordanting merino and silk wool yarn, including choosing the right mordants, preparing the fibres, and tips for getting the best results.

Understanding Mordants and Their Role

Mordants are substances that create a bond between the dye and the fibre, they help colours adhere better and last longer. Without a mordant, natural dyes may appear pale or will wash out quickly, as they lack the chemical bond that mordants provide. The most common mordants for protein fibres, such as merino and silk, are alum (potassium aluminum sulfate) and iron (ferrous sulfate). Alum is typically used for bright, true colours, while iron can produce darker, more subdued tones.

Each mordant can yield different effects on the final colour and durability, so choosing the right mordant for the desired result is important. Alum is particularly gentle on delicate fibres like merino and silk, making it an excellent choice for these luxurious yarns. Meanwhile, iron can create interesting colour variations but should be used sparingly, as it can weaken the fibres over time.

Preparing Your Yarn for Mordanting

Before mordanting, it’s essential to properly clean, or “scour,” the yarn. Scouring removes any natural oils, dirt, or residues left from processing that can prevent the mordant and dye from penetrating the fibres completely. To scour merino and silk yarn:

1. Fill a large pot with warm water, and add a gentle, pH-neutral soap.
2. Place the yarn in the pot and let it soak for about 30-40 minutes without agitating it too much to avoid felting the merino.
3. Rinse the yarn thoroughly in lukewarm water, making sure no soap remains.

After scouring, the yarn is ready to take on the mordant.

How to Mordant Merino Wool and Silk Yarn

Once the yarn is prepared, you can start the mordanting process. Here is a step-by-step guide that uses alum, which is safe and effective for both merino and silk:

Materials Needed:

• Alum (potassium aluminum sulfate)
• Cream of tartar (optional, but it can soften the wool and enhance its colour vibrancy)
• Stainless steel or enamel pot (do not use aluminum or reactive metals)

Steps:

1. Calculate the Mordant Quantity: A typical mordant ratio is 10-15% alum based on the weight of the dry yarn. For example, if you have 100 grams of yarn, use 10-15 grams of alum.
2. Dissolve the Mordant: In a large pot, dissolve the alum (and cream of tartar if using) in warm water, stirring until fully dissolved.
3. Add the Yarn: Submerge the scoured yarn in the mordant solution, ensuring it is entirely covered.
4. Heat Gently: Slowly bring the solution to a simmer (around 180°F or 80°C). Avoid boiling the solution, as this can damage delicate fibres. Let the yarn simmer for about an hour, stirring occasionally.
5. Cool and Rinse: After an hour, turn off the heat and allow the yarn to cool in the mordant bath. Once cool, rinse the yarn gently to remove any residual mordant.

The yarn is now prepared and ready for dyeing. At this point, you can proceed immediately with dyeing or store the mordanted yarn for later use.

Tips for Mordanting Merino and Silk Wool Yarn

• Work in Small Batches: Mordanting small amounts at a time allows for better colour consistency and reduces the risk of felting the merino wool.
• Avoid Excess Agitation: Merino wool is prone to felting, so handle it gently during scouring, mordanting, and during the dyeing process.
• Test Swatches: If you’re new to dyeing or experimenting with a new dye plant, test a small sample of mordanted yarn to see the colour results before dyeing the full batch.

Advanced Mordanting Techniques

For those seeking unique colours, “iron afterbaths” are another option. After dyeing the yarn with a primary dye, an iron afterbath can deepen or alter the colour. This is especially effective with tannin-rich dyes. However, since iron can weaken fibres, limit afterbath exposure to 10-20 minutes, and rinse thoroughly.

Storing and Using Mordanted Yarn

Mordanted yarn can be stored for several weeks if kept dry and away from direct sunlight. Store the yarn in a breathable bag or container to maintain its readiness for dyeing.

Conclusion

The art of mordanting merino and silk wool yarn requires patience, precision, and a gentle touch, but the rewards are well worth the effort. Through careful preparation and the use of appropriate mordants, you can achieve a range of beautiful, long-lasting colour that bring out the luxurious qualities of both merino and silk fibres.