1. Choose your fiber. Wool and silk, both animal fibers, readily absorb the deep tones of a dye, while pastels will more likely emerge in plant fibers like cotton, flax and linen.
2. Scour fibers in hot, soapy water to remove any byproducts.
3. Add about two tablespoons of alum—aluminum sulfate—to a stainless steel pot of warm water on the stove, stirring it until it dissolves. Then, add the washed fibers and simmer it all for about 30 minutes. For every pound of fiber, two tablespoons of alum help the dye bind to the material, Denbow says.
4. During mordanting, simmer flowers for 30 minutes in a second pot three-quarters full of water. Trial and error has taught Denbow the flowers-to-water ratio needed to produce rich colors—a 1-to-1 ratio for marigolds, for example, or 2-to-1 for cosmos or hibiscus.
5. After flowers have simmered, use a colander or fishbowl net to strain them from the water in the pot. “You want to get the petals out because if they rest on your fiber, they’ll leave a spot,” Denbow says.