Mordants: In order to get the natural dyes from plant material to adhere to the fabric or fibers, a color fixative or mordant is usually used to make them color-fast. What is a mordant? The term mordant derives from the French word, “mordre”, meaning ‘to bite’, and it refers to a substance when applied to the fabric before or after dyeing. A mordant is a substance, usually metallic salts–it creates a permanent bond between the natural dye and the fibers to increase dye molecules to bind or stains to fiber or fabrics. It may be used for dyeing, for intensifying stains, or change color pigments in certain plant material. To put it plainly, mordant is only required to change or affect color results. Note: Not all plant dyes need mordant to get color, as some plant dyes already has the qualities to give color without any additives. I found from my experiment that some leaf prints stays on without mordant.
~CAUTION: Please note that all powder form of chemicals should be treated as hazardous, and must be handled with care and use according to instructions. Be sure to protect yourself with an appropriate mask, eye protection (from splashes), gloves, and always work in an open environment. Do not use the containers that was previously used for storing or cooking the chemicals for cooking!
These are the some of the chemicals that I have used in my projects.
Ferrous sulfate, green vitriol, or copperas: is a modifier and as a mordant with natural dyes. Iron saddens and shifts colors. When used in dye baths it can change yellows to a range of soft to mossy greens, and reds to deep crimson reds to burgundy, or brown tones. Note: For ecological purpose, I substitute making my own “iron water/liquor” by soaking rusty objects in two parts water to one part vinegar.
Aluminum sulfate: used as a mordant to prepare pre-scoured wool and silk for natural dyeing. Per Dharma Trading, to use 1.75 teaspoon per pound of fiber. Note: This is not the same as potassium aluminum sulfate, or alum you buy at the grocery store which is used for canning and pickling.
Aluminium acetate: another useful salt for mordant pre-scoured cotton and linen (cotton has a low affinity to natural dye). Aluminium acetate is a salt obtained by reacting aluminum hydroxide and acetic acid. Jenny Dean, a famous writer and dyer in UK also recommends using it, as it is quicker, yields deeper color and also improve color fastness. Alum acetate is a fine powder, so handle with care and wear a mask for protection. Here’s a recipe from wildcolor, which I’ve used and found it helpful.
- 5 grams aluminum acetate
- 100 gms dry weight fiber (cotton, linen)
- soak fiber in warm water
- in a small container, dissolve aluminum acetate with some boiling water
- add the solution to a half-filled pot of water, add the fiber and simmer the solution for an hour (add more water if needed). Remove from heat, covered and let it cool overnight.
- the next day, remove the fiber, rinse well and it is ready for dyeing. (I’d tried drying them and kept it for a few days. When I am ready to dye or make my prints, I simply rinsed it well.
Copper (copper sulphate): enhance greens and tend to lighten colors. Note: if you use copper, dispose it with care and don’t pour it outside or down drain as it is harmful to waterways and wetlands. Click here to read about how to properly dispose the solution.
Vinegar (acetic acid) and lemon juice are acidic substances that are not true mordant. However, they act as a modifier to shift a colors in certain dye color. It is used often to lower the pH of soap residue in wool after the final process of felting, and acts as a wool conditioner.
In the past months, I have tested various combinations of different plant materials on fabrics, dyes, and mordant to see how they print and color fabrics. I put these results in a notebook for my future references. It’s a bit like a recipe book. I have a few good and many not so good results. I appreciate any comments, however big or small. Please note that this list will be updated from time to time.