Mordanting Fabric (Oak Gallnut)

Welcome back to Plants to Dye For – Season 2! In this episode, we're using ground oak gallnut as a mordant for our fabric. Mordants help bind dye to fiber, and improve color fastness. We learned about mordants last year (see Mordants and Fixatives), and used gallnut as a mordant for our weld project (see Dye Project: Weld Extract). Now we'll go a little deeper into the details of mordanting. This year I'm experimenting with processing dish towels in advance, so I have a large quantity on hand for projects.

I'm using oak gallnut extract from Maiwa. Gallnut is a clear tannin, and made from ground oak galls, which are rich in tannins. The galls are harvested, dried, and ground to a powder. Oak galls are created by parasitic wasps, which use genetic engineering to create their nurseries.





The basic process (based on Sasha Duerr's The Handbook of Natural Plant Dyes):

1. Presoak the scoured fabric.
2. Simmer the gallnut in water.
3. Add fabric and soak.
4. Rinse the fabric in cold water.

Stainless steel pots

For equipment I'm using a large plastic bucket from the hardware store, a large stainless steel pot, a candy thermometer, and a heat source. Last year, one of my aluminum pots was stained from onion skin dye, and the color may have influenced the outcome of the weld dye color. This year I thrifted a couple of stainless-steel pots, which should help prevent color transfer. The candy thermometer is important because the mordant works best if the tannin bath temperature does not exceed 180 degrees F (or 82 degrees C). You can work in the kitchen for this project, but always ensure ventilation. For safety, wear a face mask when measuring powders, so you don't inhale small particles.

Oak gallnut extract for mordanting fabric

According to Maiwa, the Weight of Fabric % for gallnut is:

• 12% WOF for Gallnut powder
• 6-8% WOF for Gallnut Extract (which we are using)

We'll use 8% WOF for our dish towels and T-shirt. We have two batches of towels, each weighing just over a pound or 462 g. For each pound of fabric:

•  3 tablespoons powdered oak gall extract
• 2-4 gallons of water (I used about 3 gallons)

First, soak the pre-washed and scoured fabric in a bucket of hot water for at least and hour (or overnight). This helps ensure that the fiber soaks up the gallnut evenly.

Soak the pre-washed and scoured fabric

After pre-soaking the scoured fabric:

1. Place the gallnut extract in a pot of water, and stir to dissolve.
2. Bring the tannin solution to a simmer, keeping it under 180 degrees Fahrenheit (or 82 degrees Celsius), and then simmer for 30-60 minutes.
3. Remove the tannin pot from the heat and let cool.
4. Lift the dish towels out of the soaking pot, squeeze out excess water, and add them to the tannin pot.
5. Steep the towels in the tannin pot for 8-24 hours.
6. Rinse the towels thoroughly in cool water, and then use the rinse and spin cycles on your washing machine.

Multiple batches of pre-processed fabric hang to dry

At this point, you are ready to dye the wet fabric; further treat it with an alum brightener; or hang it to dry and store the fabric until you are ready to dye. For today's video, we are labeling the fabric for storage, with plans to dye at a later time.

Label and store the fabric

In closing, I've found that none of these processes—like scouring and mordanting—are difficult. But they take time, often stretching over several days if you use the maximum recommended soaking time. Much of that time is spent soaking the fabric in various baths. I'm hoping that processing several batches early, will save time later when I'm ready to dye.