Can Soil Be Used as a Natural Dye? How to Make Dirt Shirts
Several variations can be used for this activity. First have the students make a hypothesis about what will happen when white cotton material is submerged in mud (of various colors). For the scientist, the first hypothesis will state that the treatment will not affect the color of the cloth. this is called the null hypothesis, or hypothesis of no difference. The scientist will then have an alternative hypothesis that says the soil will change the color of the cloth.
Bright red and yellow soils are the most effective dyes due to the type of iron present in those soils. (Red is oxidized, anhydrous, Fe2O3, a hematite mineral; Yellow is oxidized, hydrated, 2Fe2O3Â·3H2O, a limonite mineral.) Soils are usually dark because of organic matter, or humus, though there are other minerals that sometimes result in dark soil colors.
The white t-shirt below was dyed in the mud of the Double Mountain Fork of the Brazos River, just of US 70 in Texas. The left photo shows the contrasting original color of the shirt with the Brazos mud. The right photo shows the same shirt, once it was muddied and rinsed in the river. The color fades with washing, but will never again be white. Click on the photos for a larger image.
- Soils - minimum of one bright or dark red or yellow soil, other soils can be used if desired
- Soda Ash - mix the soda ash and soak the cloth before putting the wet cloth into the mud. For information about Soda Ash, see this website: http://www.pburch.net/dyeing/FAQ/sodaash.shtml. Soda ash is the common name for sodium carbonate (but is not the same as baking soda, sodium bicarbonate).
Vinegar is used in the mud mixture, or as a post-treatment rinse, approximately 1 cup of vinegar for each gallon of water. The vinegar alters the pH of the mixture, which causes the iron pigments in the soil to be more soluble, and so more easily transferred to the fibers. The end result is a more colorfast dye
- Water temperature can be used as a variable, hot water generally is more effective than cold water. (Cloth-mud mixtures can be boiled.)
- Color Enhancers: Anhydrous iron oxide (FE2O3), will enhance the red color.
- Wash and dry the shirts first with a standard detergent.
- Pretreat cloth, if that is desired.
- Make mud, it needs to be thin enough that you can easily work the soil into the cloth. I have never measured the quantities, but use a slurry mixture. The soil-water mixture needs to be dilute enough to easily flow. I suspect I am using 2 to 4 parts water for every 1 part soil.
- Allow the cloth to soak in the mud for 4 hours or more. Agitation allows more mud/fiber contact. Heat can be applied in this step.
- Rinse the cloth. Vinegar can be used in this step.
- After allowing the cloth to dry, it can be washed in cold water to determine the amount of color set. Washing will fade the color as some soil particles will be removed from the cloth.
- Dry in a hot dryer after rinsing in cold water.
- Check the outcome against the original hypothesis.
Additional Comments from Dr. Dirt:
"Shirts can be tied or knotted, etc., for a tie-dye effect.
I am not sure that I have noticed any real difference using pretreatments with soil dyes, but it is useful with other natural dyes.
Personally, I have had better results with soil when running the shirts through the soil mixture more than once. The first time through the complete cycle to drying sets a light color. The second time through the soil-vinegar solution sets a darker color.
I have not used potters clays, though I have considered it (having recently encountered some potters ...)."