Dye Like a Natural
Stain your clothes on purpose, bringing the colors of nature to your own wardrobe: use colorful molecules found in natural organisms and objects to dye fabrics or other textiles.
- Colorful fruits and vegetables—onion skins, carrot tops, blueberries, raspberries, hibiscus tea, beets, or anything else you want to try
- One or more mordants—copper sulfate, tin(II) chloride, alum (available in grocery stores), or any other polyvalent metal compound
- Cream of tartar
- Substrate material—un-dyed wool yarn, cotton string or fabric, or other natural material
- Paper towels
- Hot plate or other heat source with temperature control
- Several heat-proof containers (one for each type of mordant and dye)
- Prepare the mordants. You may have to heat the solution to help the solutes dissolve. Make enough to completely cover the amount of substrate you want to dye. Here are some suggested concentrations:
- Copper: 2g CuSO4∙5H20 in 100 ml water
- Tin: 0.5g SnCl2 and 2.5g cream of tartar in 100 ml water
- Aluminum: 2g alum and 1g cream of tartar in 100 ml water
- Cut your substrate material into strips or small pieces. Try to have at least one piece for every combination of mordant and dye that you are using. Tie knots in your samples to help keep track of which mordant is being applied. Here’s one way to do it:
- Knot near one end = copper
- Knot in the center = tin
- Knot at each end = aluminum
- No knot = no mordant
Dampen your samples with water. Submerge each sample in its proper mordant solution and simmer each mordant in a separate heat-proof container, just below boiling, for 30 minutes. Set the sample that won't receive a mordant aside for now.
While your samples are simmering in the mordant solutions, prepare the dyes. Chop or cut up each dye source, place the pieces in a pot or bowl, and cover with hot water as if you were making tea. Let everything steep for 15-30 minutes. You may want to simmer the dye ingredients over a heat source if the solution doesn’t seem to be darkening. Strain out any solids. Do this separately for each dye source that you are using.
When your samples are finished mordanting, pat with a paper towel to eliminate drips, then place a sample from each mordant solution into the separate dye baths. Leave the material in the dye solution for a minimum of 15 minutes or until you see they have taken up color. You may get enhanced results by leaving them in the dye solution longer.
Finally, give each piece of substrate a quick rinse with water, set it out to dry, then compare the color and effectiveness of the different mordant/dye combinations on the different substrates. What do you notice?
The art of natural dyeing utilizes dyes and substrates that are both derived from plant or animal sources. Dyes are typically organic compounds that contain double bonds where electrons can be delocalized, such as a benzene ring or nitro group, called chromophores. When light hits these chromophores, the energy of a specific wavelength is absorbed, and the rest is reflected, resulting in our perception of a colored substance. Dyes also have a chemical group, which is usually charged, that can bind to a substrate material. These will form ionic or hydrogen bonds with a charged portion of the substrate, such as keratin in wool or cellulose in cotton.
Mordants are metal cations that act as bridges between dye molecules and fabric. Metals such as copper, aluminum, and tin have valencies of +2 or +3 that allow multiple electron donors to bond. Instead of bonding to each other, the dyes and substrates have chemical groups such as hydroxl and/or carbonyl groups that form covalent bonds to the metal cation, which sits between them. These bonds are stronger than the ionic or hydrogen bonds that would attach the dye directly to the substrate, which results in a longer-lasting color. The multiple sites also allow more dye molecules to attach, which yields a deeper color. The best mordant to use will depend on the chemistry of the specific dye and substrate. Which one works best for the system you tried?
This Snack is based on activities found in The Chemistry of Natural Dyes by Dianne N. Epp.