This week we explored the world of natural dyes, relying on the expertise of Alejandra. We dyed white and grey wool with three dyes: indigo, marigold, and logwood. All three are plant-based: indigo and marigold are flowers, while logwood is a large, flowering tree. All of these dyes were historically used in Central and South America from the pre-colonial period. Indigo and logwood were cultivated on a large scale for export to Europe by various colonial governments, and marigold remains an important cultural plant used during the Dia de los Muertos.
The marigold and indigo used in the lab were grown in Alejandra’s dye garden; rather than the South American species of indigo, Alejandra grows Japanese Indigo because it deals with cold weather more easily. The logwood was obtained from a dye manufacturer.
Two distinct dye processes were used. For logwood and marigold, the dried plants were steeped in boiling water with the yarn for about an hour each. Beforehand, the yarn was soaked in a warm alum solution for an hour; the alum acted as a mordant. We also noted that these dyes were boiled in cast-iron pots; according to botanicalcolors.com, iron acts to lower the value of (i.e. darken) a natural dye (https://botanicalcolors.com/botanical-colors-how-tos/how-to-use-iron-powder-ferrous-sulfate/). However, we do not know to what extent the iron pot – rather than powdered iron – affected the final product.
Alejandra prepared an indigo bath before the lab started. This was a strong solution of indigo, lime, and fructose. The lime acts as an acid to reduce the solution to a target of 10ph (indigo is very basic). Fructose acts to remove oxygen from the mixture; an indigo solution with too much or not enough oxygen will not dye properly (https://botanicalcolors.com/botanical-colors-how-tos/botanical-colors-faq/indigo-faq/#:~:text=Oxidation%3A%20Oxidation%20is%20when%20the,the%20blue%20color%20to%20emerge.).
Table 1 shows the amount of dyestuff, mordant, and water used in each case, and the timing.
| Dye: | Part of the plant/preparation | Amount used: | Other ingredients: | Mordant: | Time: |
| Indigo | entire plant; dried and crushed to extract dye | ? | fructose, lime | —— | 5 sec. |
| Marigold | whole flowers, dried | 100g | ——- | alum, 1tbsp/100g of wool | 60 min. |
| Logwood | shredded woodchips | 50g | ——- | alum, 1tbsp/100g of wool | 52 min. |
In addition to the six hanks of wool (three grey, two white) dyed using the pure dyes, two more were dyed with marigold and then indigo. Also, we took the opportunity to dye several clumps of wool in indigo, along with shoelaces, cotton shorts, human hair, and human skin. The results from our wool-dyeing are detailed in table 2, and gallery 1 shows a set of images. I am describing the colors using the “Martian color wheel” found on Warren Mars’ website (https://warrenmars.com/visual_art/theory/colour_wheel/colour_wheel.htm).
| Dye: | White yarn | Grey yarn | Raw wool: Leicester Longwool (originally white and very curly) | Raw wool: Jacobs (originally brown and grey; not curly) | Carded wool: Leicester Longwool |
| Marigold | Yellow cheese | Yellow cheese (very slightly darker than white yarn) | ——— | —– | ——– |
| Indigo | Powder blue | Sky blue | Azure blue; patches of white | Powder blue; patches of dark grey | Dark azure |
| Logwood | Delphinium blue | Royal blue | ———- | ——- | ——- |
| Indigo+Marigold | Olive | Olive drab | ——— | ——- | ——- |
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