Scouring your Fabric

Today I'm taking a closer look at the scouring process. After the mixed results of the cabbage dyeing project (see Dye Project: Red Cabbage), I realized I better learn a little more about scouring fabric! Scouring (or scrubbing) is the process of removing waxes, oils, sizing, or finishes from the fabric that could prevent dye from binding to the fiber. We'll try two projects, using two different recipes (one uses Synthrapol and soda ash, and the other uses Dawn dish washing liquid and soda ash).




For both projects, I used our patio as an outdoor studio. This may not be necessary from a ventilation point of view for these projects, but I like having the opportunity to work outdoors when I can.

Preparing to scour plant-based fabric in the outdoor studio

Before dyeing, it's important to pre-wash your fabric in the washing machine using detergent. But, pre-washing may not be enough to remove all impurities from the fibers. Even our sparkling white cotton dish towels may have layers of manufacturing residue that remain. To remove these impurities, use scouring agents, such as:

• Neutral soap - like Dawn dish washing liquid, or Synthrapol
• Washing soda - like Borax, soda ash, or soda crystals

Synthrapol is made of water, isopropanol alcohol, and detergent. The detergent molecules surround impurities on the fiber, and water rinses them away. Soda ash (sodium carbonate) neutralizes the pH making it easier for dye to bond to fibers. 

Pre-washed fabric may still contain impurities that prevent dye from bonding to fibers

You can use the weight of your fabric to estimate the quantity of scouring agents to use, but, unlike mordanting and dyeing, it is more of a guideline than a rule. I have found that three cotton dish towels and one gallon of water fit well in each of my aluminum pots, allowing room to simmer. Three dish towels weigh about 8 ounces (231g).

The basic process for scouring is:

1. Pre-wash your fabric with detergent
2. Fill a large pot with water and stir in scouring agents.
3. Add fabric and more water so the fabric is covered but not crowded.
4. Simmer for an hour or two (or soak overnight)
5. Rinse in cold water, then wash in the washing machine without detergent. Optionally add an extra rinse cycle.
6. Use towels while wet or hang to dry to use later.

Project 1: scouring with Synthrapol and soda ash

For the first project, scouring was done with Synthrapol and soda ash. I used two pots to scour six dish towels, and used the following recipe for each pot:

• 4 quarts water brought to a boil
• 1/2 teaspoon Synthrapol
• 2 teaspoons soda ash
• 3 pre-washed dish towels (about one half pound or 231g)

I let the pot simmer for a couple of hours. Initially I had trouble with sudsy water spilling over the pot, but finally worked out the temperature and water level to achieve a simmer. After half an hour, the water started to turn brown. At the end of a couple of hours, I removed the towels, rinsed thoroughly, and then washed them in the washing machine with no detergent and an extra rinse cycle. I let them air dry for future use. 

The water started turning brown after a half hour of simmering

It was surprising to see how brown the water turned. This is from the impurities that were removed from the fibers.

Note that I found out later that Dharma Trading Company carries a suds-free Synthrapol, which might be worth trying, especially here in the San Francisco Bay Area, where we always have an eye on water conservation. 

Project 2: scouring with Dawn dish washing liquid and soda ash

For the second project, scouring was done with Dawn and soda ash. I used one pot to scour three dish towels, and used this recipe for one pot:

• 4 quarts water brought to a boil
• 1/2 teaspoon Dawn dish washing liquid
• 1 tablespoon soda ash
• 3 pre-washed dish towels (about one half pound or 231g)

I followed the same procedure described in the first project with similar results. After half an hour, the water started to turn brown.

More brown water

I wondered whether the blue Dawn might contain dyes that could themselves bond to the fibers, but that didn't seem to be the case (unless it manifests in a later dye project)! Also, the Dawn seemed sudsier than the Synthrapol, so I wondered whether additional water might be needed for rinsing. But the end result was the same: lots of satisfyingly brown water was produced!

Very satisfying results!

For both projects, you can immerse the wet fabric immediately into your mordant or dye bath. Or you can air-dry the fabric and store until needed. It is a good idea to label it, so you know that the fabric was scoured.

Pre-washed and scoured - ready for dyeing!