Updated: Feb 15, 2021
Best Mordants to Use With Natural Dyes:
There are many mordants you can choose but I believe the following are the best mordants to use when natural dyeing. One of the most important elements of natural dyeing is the use of a mordant or fixative. When dyeing protein fibers such as wool or silk, mordanting allows the dye to properly adhere to the fiber without fading or rinsing away. With plant- based (cellulose) textiles like linen or cotton, a fixative is needed to help the dye set properly. Some mordants, like aluminum sulfate, can be used for protein fibers and certain cellulose fibers. Certain natural dyes and fibers will bond with each other on their own, so it is recommended to research the suggested combinations of dyes, mordants (or lack of), and fibers. Those who are advanced dyers may use mordanting as a way to alter the color of a dye or even to add pattern to a fabric they are dyeing.
Some of the best and most commonly used mordants and fixatives to use with natural dyes are alum (potassium aluminum sulfate or aluminum acetate) and cream of tartar. When mordanting fibers, it is always recommended to work in a well-ventilated room and wear a dust mask along with an apron and gloves.
Yarn I dyed using alum + madder root
To mordant your natural fiber with aluminum acetate, you should use 5-10% of the weight of fiber. This is about the same as 2-4 rounded teaspoons for every 100 grams of fiber. Add some cool water to your alum to give it a paste-like consistency and then use boiling water to dissolve it. Fill your stainless steel dye pot with hot water, (110-120 degrees Fahrenheit), and add your dissolved alum, stirring well. Now add your fiber to the pot, making sure it’s fully submerged, and stir gently. For about 45 minutes, hold the heat and continue to occasionally stir the contents of your dye pot and make sure you are also pressing on the fibers to eliminate any air bubbles that may form. After 45 minutes, remove your fibers from the dye pot. There is no need to rinse them.
If you’re mordanting cellulose or cotton, you need to fix the alum to the fibers before you’re ready to dye. You can use a calcium carbonate bath to do this, using about 5% of the weight of fiber or 1 rounded teaspoon for every 100 grams of fiber. Add your calcium carbonate to a large container of water that is boiling hot. Add your mordanted fiber to this container and allow it to rest for up to 30 minutes. Once this is done, you can remove your fibers from the mixture and place them straight in the dye pot with no need to rinse in between.
Cream of Tartar:
Cream of tartar is a fixative sometimes added to alum mordant baths when mordanting animal or protein fibers like wool and alpaca. It is great for brightening shades, improving consistency of color, softening wool, and producing an overall clearer end result in your color. It will also shift the color of some natural dyes such as madder, cochineal, and lac. It is recommended to use cream of tartar at about 5-6% of the weight of the fiber. Just dissolve your cream of tartar separately from your mordant and add it to the pot along with your dissolved mordant.
Please let me know what kind of results you get and have fun!!