SCOURING & MORDANTING
Scouring and mordanting are the two essential steps to prepare a textile for accepting dye. Dyeing textiles that have not been properly scoured and mordanted can result in spotty color, color impermanence, or a lack of dye uptake altogether. Basically: don’t skip these steps! They are necessary in creating vibrant, lasting plant color that will withstand light exposure, washing, and wear.
The following instructions apply to plant fibers (cotton, hemp, bamboo, linen) only – the scouring process for animal fibers (silk, wool) is different. Plant fibers are my area of expertise, so I urge you to do your own research on these processes if you’re working with animal fibers.
Scouring
Scouring is the process of thoroughly washing your textile to remove any sizing, wax, dirt, or other contaminants present from the manufacturing process, gently stripping and readying the fibers to absorb mordant and dye.
This process is specifically done with soda ash (a.k.a. sodium carbonate) – not regular detergent. Soda ash is a naturally occurring compound with gentle alkalinity, historically sourced from the ashes of plants growing in sodium-rich soils, which is where the common name comes from!
Materials needed:
Non-reactive dye pot *
Measuring spoons **
Stirring spoon **
Heat source
Water
Optional (but highly recommended):
Kitchen scale
Cooking thermometer
Scouring instructions:
Measure out soda ash at 1-2% the dry weight of fiber (w.o.f.).
e.g. If fiber weight is 100 grams, measure out 1-2 grams of soda ash.
(1/4 to 1/2 teaspoon per 100 grams of fiber is an approx. equivalent.)
Fill a dye pot with warm tap water, allowing enough room for the textile to move freely.
Add soda ash and stir until completely dissolved.
Add textile to the bath and immerse completely.
Slowly increase water to just below boiling, 180-200º F, rotating the textile gently and consistently.
Maintain at temperature for 30 minutes, ensuring the textile remains completely immersed in the bath.
Turn off heat and let the textile cool in the bath.
Once at room temperature, remove the textile and rinse thoroughly with same temperature tap water.
Gently wring out excess water from the textile and proceed to mordanting.
NOTE: If scour bath is very cloudy or dirty when finished, repeat the scouring process.
Mordanting
A mordant (French for “to bite”) is a substance applied to a textile that acts as a translator between fiber and dye, allowing the two to form a permanent chemical bond. Without a mordant, natural dyes typically form only loose chemical bonds with a textile, and are likely to fade or wash out.
The most common and effective mordant for use on plant fibers is alum, a naturally occurring mineral used as far back as Ancient Egypt. Today, “alum” refers to a number of mineral compounds, with aluminum acetate being the most suitable for mordanting plant fibers. In its various forms, alum is used for dyeing, paper making, leather tanning, water purification, and even pickling foods!
Materials needed:
Alum (aluminum acetate)
Kitchen scale (measures in whole gram increments)
Non-reactive dye pot *
Measuring spoons **
Stirring spoon **
Cheesecloth or mesh bag
Hot water
Optional (but recommended):
Cooking thermometer
Food-grade bucket or separate non-reactive dye pot
NOTE: Alum is a fine powder that can be corrosive to skin and is harmful if inhaled. Please wear gloves and a mask when handling alum, and work in a well-ventilated space.
Mordanting instructions:
Measure out alum at 10% the weight of fiber (w.o.f.).
e.g. If fiber weight is 100 grams, measure out 10 grams of alum.
(3 to 4 heaping teaspoons per 100 grams of fiber is an approx. equivalent.)
Measure out wheat bran at 5% w.o.f.
(4 teaspoons per 100 grams of fiber is an approx. equivalent.)
Fill a dye pot with hot tap water (110-120º F), allowing enough room for the textile to move freely.
Add alum and stir until completely dissolved.
Add textile to the bath and immerse completely.
Loosen any folds or creases in the textile to allow for even mordant uptake.
Rotate gently and consistently, ensuring the textile remains completely immersed in the bath.
Remove textile from the bath after 45 minutes. Gently wring out excess water, but DO NOT RINSE.
Wash the dye pot you’ve been using or prepare a secondary vessel (food-grade plastic bucket or separate dye pot) for wheat bran bath.
Gather wheat bran in cheesecloth or mesh bag and fill your pot or bucket with just enough hot tap water to immerse the wheat bran bundle.
Soak wheat bran for 30 minutes. The water will turn milky and cloudy.
Refresh the wheat bran bath with plenty of hot tap water, and immerse the textile.
Gently squeeze the bundle of wheat bran to draw out more minerals.
These very minerals are what enhance your dye colors, making them vivid and bright!
Rotate the textile gently and consistently, leaving in the bath for 30 minutes.
Remove fibers from the bath and wring out excess water, but DO NOT RINSE.
Proceed to dyeing!
Some dyers prefer to leave their textiles in the alum bath overnight, and find that this increases the vibrancy of dye color.
After the entire mordanting process is finished, you may choose to dry your textiles completely and store them for dyeing later. For even dye uptake, textiles that have been mordanted and dried must be fully wetted out before being introduced to the dye pot.
Alum baths can be reused at least twice. If the bath turns cloudy or floating residue appears, it’s time to refresh. Charge the bath with approx. half of the required mordant, or 1-2 teaspoons per 100 grams of fiber. Wheat bran baths last only 1-3 days, but can be reused as long as the mixture remains cloudy and no bubbles/funky smell are present.
* Stainless steel or enamel are considered non-reactive cookware. “Reactive” metals like aluminum, iron, tin, or copper (and more) will alter dye results, or sometimes render them ineffective.
** All kitchenware and utensils used for dye projects should be reserved for dyeing only. It’s dangerous to prepare or consume food made with pots or utensils that have come in contact with substances used for dyeing.