I'm going for fabric in which the process leaves its mark -- irregular, organic marks, as well as color.
Most of my natural dyeing involves putting dyestuff in direct contact with fabric. Sometimes it's a slow process in which fabric and dyestuff are wrapped together with copper or steel wire, the bundle is tucked into a plastic bag and splashed with vinegar or old wine, then left in the sun for a week or two (longer, if sun isn't part of the equation).
Lately, I've been playing with the balance between heat and time. Much of this exploration was inspired by India Flint. After a comment she made at the Surface Design conference in Minneapolis last summer, it seemed like serendipity that I should find a rice steamer at my local thrift shop. I started playing with it during goldenrod season. And I'm loving it with willow.
What I do is wrap my dyestuff (willow leaves and/or bark, bits of metal, etc.) in fabric moistened with water or willow dye liquid, then wrap the bundle in baking parchment. Some bundles I let sit overnight first, some get steamed right away. A bundle is steamed on a rack over hot water for an hour or so. I have to add water about every 20 minutes. After steaming, I let the bundle cool. I might pull the metal out of the bundle the same day on a silk piece, but I try (try, I say) to let the bundle mellow overnight before unwrapping it.
Steaming isn't the only way I apply heat. I also simmer bundles in willow dye liquid in a saucepan on a hotplate in my studio. Because the metal in the bundles leaches into the dye liquid, I may only get a couple of bundles simmered before the color starts to get dull. Bundle simmering has been successful enough for me to take a second saucepan (cast aluminum) from kitchen duty and dedicate it to the studio.
The biggest problem I have with simmering bundles is controlling the temperature on the electric hotplate (a garage sale purchase). With too much heat, silk can lose its luster. With the smaller saucepans, I have better results when I never turn the dial past the halfway point and just let it come up to below-simmer sloooowly.
The second-biggest problem I have with simmering bundles, I'll save for tomorrow. I'm working on pacing and patience. It's a challenge!