Scouring is a term meaning to clean or brighten the surface. Possibly derived from a Late Latin verb, excurare, meaning "to clean off" or Old Norse skūr, meaning "shower." Some people believe you can scour in a washing machine, but it is my finding that a washing machine does not suffice as it does not get hot enough, for long enough. In order for mordants and dyes to adhere well to the fiber they must be clean and fully scoured. This is one step you do not want to skip. It also helps to ensure an even dye job, when dyeing solid colors.
Supplies needed: item for dyeing, non reactive (stainless steel) pot, rinse bucket, spoon or tongs, scale, ph neutral soap, soda ash, heat source (stovetop, induction cooktop, gas cooktop etc), pen and paper
1. Start by weighing your item while it is completely dry, this will be your "weight of fiber" which will be referred to as "WOF" from now on. Document this number for future use. Good record keeping is KEY to successfully natural dyeing! Not only does it make calculations easier, but it also saves time if dyeing the same item later on. For example, if a large, organic cotton tee shirt weighs 200g, we know that 1% WOF is 2g, 2% WOF is 4g and 10% WOF is 20g. I like to use grams, over ounces, for a more accurate read. In the future if I am dyeing the same item, from the same source, I can use the same calculations.
2. Scouring your item prepares your item for mordanting and/or dyeing. Even if you are using a substantive dye, which bonds with the fiber without the use of a mordant, you will still need to scour. Scouring removes dirt, wax and oils and is especially important when using cellulose fiber. Always scour in a non-reactive (stainless steel) pot. Be sure that your pot is large enough to contain your item. Your item should be able to float freely in the pot. Start by adding your dry item to an empty pot, then fill your pot with tap water. I like to allow my item to be fully wetted (15-30 minutes), then add 5% WOF ph neutral soap (Synthrapol® soap or Seventh Generation are good choices) and 1-2% WOF soda ash. NOTE: When measuring powdered chemicals, always wear a dust mask. Heat on high (around 180°F) for 1-2 hours. Up to 2 hours for cotton.
3. When scouring is complete, you will notice that the water is a cloudy beige color. Turn your heat source off. While the pot is still hot, remove your item. Do not let fiber cool in the scour water. In order to do this safely, I like to put a rinse bucket right next to the scour pot and using a spoon or tongs, carefully pull the item out of the scour pot and transfer it into the rinse bucket. Next, you will rinse your item really well. Optionally, you can add a dash of vinegar to your rinse bucket to neutralize the alkalinity caused by the soda ash. If the scour water is extremely contaminated, you can choose to scour again. Proceed to mordanting.
Natural dyer, natural dye educator, maker and all around textile nerd.