the chemistry of dyeing
Because it is a chemical process that requires the right amount of heat, time, and ingredients, it cannot be rushed.
While it is not necessary to return to high school chemistry in order to dye wool, it helps to understand the three simple phases of the chemical process that fix the dyes to the fibers. Becoming familiar with the three phases of the dye process gives us insight into what is happening to the wool at various stages in the process: why we are applying heat, adding citric acid, increasing the temperature, and patiently waiting. It helps us know what to do to adjust the process when our wool spots or the dye does not penetrate evenly.
it’s all chemistry.
dye approach.
When the wool is immersed in the dye solution, as the solution heats up, the dye molecules begin to move to the fiber surface. The wool swells with water making the penetration of the dye into the fiber easier.
dye migration.
The dye begins to migrate and level now. During this phase, the dyes move in and out of the fibers and solution. It migrates from darker to lighter areas of the fibers as the dye distributes itself evenly across the wool. When the color finally appears equally distributed over the wool, the dye will have reached an equilibrium and will be ready to be fixed by lowering the pH.
Dye Fixation.
This happens when the wool is removed from the dye bath and the mild acid like citric acid is put into the solution. Citric acid is a mordant that lowers the pH of the dye bath and forces the dye molecules to bond with the wool fiber. When the wool is returned to the dye bath, immediately the dye molecules interact with the wool fiber surface in the magic chemical reaction. The temperature is raised slightly for another 60 minutes until the dye bonds inside the fiber.