Onion skins are an accessible and natural dye source that can produce a beautiful range of earthy hues, from golden yellows to deep rust tones. Using onion skin dye is a favorite among eco-conscious crafters and those exploring sustainable textile practices. However, to make the color long-lasting and vibrant, using a mordant is essential. A mordant helps the dye bind better to fabric, ensuring the results are both wash-fast and light-fast. Understanding how to use a mordant properly with onion skin dye is a key step in successful natural dyeing.
Understanding Mordants
A mordant is a substance used to fix dyes onto fibers. In natural dyeing, mordants help ensure that the colors penetrate the fabric thoroughly and remain vibrant over time. Without a mordant, many natural dyes will either fade quickly or not bond well with the fiber. The word mordant comes from the Latin word mordere, which means to bite, symbolizing how the mordant helps the dye bite into the fabric.
Common Mordants for Onion Skin Dye
- Alum (Potassium Aluminum Sulfate): This is the most commonly used mordant in natural dyeing. It’s non-toxic and provides clear, bright shades when used with onion skins.
- Iron (Ferrous Sulfate): Iron can darken the colors from onion skins, shifting them from yellow to more olive or brownish tones.
- Tannin: Tannin-rich substances like oak galls or tea can be used as a pre-mordant or assist with colorfastness, especially on plant-based fibers.
- Cream of Tartar: Often used alongside alum to soften the final tone or enhance brightness.
Why Mordanting Is Important in Onion Skin Dyeing
Onion skins are classified as substantive dyes, meaning they contain some natural mordanting properties. They can sometimes dye wool and silk without added mordants, but for lasting results especially on cellulose fibers like cotton mordanting is highly recommended. Using a mordant allows the color to adhere more strongly, resulting in richer, longer-lasting shades that resist washing and fading.
Preparing Fabric for Mordanting
Before applying a mordant, it’s important to prepare your fabric properly. This step ensures that the fibers are clean and ready to receive both the mordant and the dye. The preparation process includes scouring and sometimes using a tannin bath.
Steps for Fabric Preparation
- Scour the fabric: Wash wool or silk in warm water with a small amount of gentle soap. For cotton or linen, boil it with soda ash or washing soda to remove any oils or sizing.
- Rinse thoroughly: After scouring, rinse the fabric well to remove any remaining soap or soda ash.
- Optional tannin bath: For plant-based fabrics, a soak in tannin-rich solution for several hours can improve dye uptake and mordant adhesion.
Mordanting with Alum
Ingredients and Materials
- 10-15% alum by weight of fabric (WOF)
- 5% cream of tartar (optional, used with wool or silk)
- Large stainless steel or enamel pot
- Water
- Prepared, clean fabric
Steps to Mordant Fabric with Alum
- Fill the pot with enough warm water to submerge your fabric completely.
- Dissolve the alum (and cream of tartar if used) in a small amount of hot water, then add it to the pot.
- Add the wet fabric to the pot and gently heat the mixture to about 80°C (176°F). Avoid boiling.
- Maintain the temperature and stir occasionally for about one hour.
- Let the fabric cool in the mordant bath for several hours or overnight for best results.
- Rinse the fabric thoroughly before moving to the dyeing stage.
Creating the Onion Skin Dye Bath
While the fabric is mordanting or soaking, you can prepare your onion skin dye bath. You can use either yellow or red onion skins, with yellow yielding brighter golden tones and red producing more coppery or even greenish shades depending on the mordant used.
How to Make the Dye Bath
- Collect a generous amount of dry onion skins around 50-100 grams per 100 grams of fabric.
- Place the skins in a large pot and add enough water to cover them by several inches.
- Bring the mixture to a gentle simmer and let it cook for 30-60 minutes. The water should turn a deep amber or reddish hue.
- Strain out the skins and save the colored liquid. This is your dye bath.
Dyeing the Mordanted Fabric
Once your fabric has been mordanted and your dye bath is ready, it’s time to bring everything together. The key here is patience and gentle handling, especially with delicate fibers like wool and silk.
Dyeing Process
- Wet the mordanted fabric with clean water.
- Place the fabric in the dye bath and heat gently to around 60-80°C (140-176°F). Do not boil, as this can damage wool and alter the final color.
- Simmer for 30-60 minutes, stirring occasionally to ensure even dyeing.
- Turn off the heat and allow the fabric to soak for several hours or overnight for deeper color.
- Remove the fabric, rinse with cool water, and hang to dry away from direct sunlight.
Modifying the Color with Iron Mordant
If you want to create darker or more muted tones, you can apply an iron mordant either before or after dyeing. Post-dyeing modification with iron can create olive, brown, or bronze hues from onion skin dyes.
Iron Mordant Application
- Dissolve a small amount (1-2% WOF) of ferrous sulfate in water.
- After dyeing, soak the fabric in the iron solution for 5-15 minutes.
- Watch the color change gradually and remove the fabric once the desired tone is achieved.
- Rinse thoroughly to remove excess iron and prevent long-term fiber damage.
Caring for Onion Skin Dyed Fabrics
Natural dyes are more delicate than synthetic dyes, so care should be taken to preserve their beauty. To keep your dyed items vibrant, wash them gently and avoid prolonged sun exposure.
Tips for Long-Lasting Results
- Hand-wash in cold water with a mild, pH-neutral soap
- Avoid machine washing or harsh detergents
- Store away from direct sunlight
- Iron on low heat if needed
Using an appropriate mordant with onion skin dye unlocks the full potential of this humble kitchen waste. The variety of tones and effects you can achieve from golden yellows to mossy greens depends not only on the type of onion skin but also on the mordanting method you choose. By understanding how alum, iron, and tannin interact with fabric and dye, you can transform simple materials into beautifully dyed textiles. Whether you’re an experienced dyer or just starting out, mordanting opens up a world of creative color possibilities using nothing more than nature’s leftovers and your imagination.