Each week, we are emailed with questions from our natural dye community asking simple and complex questions that we thought might be worth sharing. Here are a handful from this week answered by natural dyer in chief, Kathy Hattori, Founder of Botanical Colors:
I often hear about “fugitive color.” Can you tell me why some colors like turmeric can latch onto fabric and why others like beets can’t?
The terms “fast” and “fugitive” (not Fast and Furious) refer to how durable a natural color is to light, heat, and washing. “Fast” means that the color is durable and its strength is measured on a scale of 1 to 5, with 5 being excellent in both fastness to washing and to light. It’s often combined as the term “colorfast”, “lighfast” or “washfast.”
“Fugitive” means that the color is not durable. One of the reasons why beets won’t dye and turmeric will is the type of color that is within the plant. Beets have a color that is sensitive to both light and heat, so beet juice degrades quickly under these conditions. Turmeric has a color that is more fast to light and heat, but it too, is considered a fugitive color as it doesn’t hold up for any length of time.
I’ve heard that rusty nails can be used as a mordant, are there any other things like that around the house that can be used?
Rusty nails make an iron oxide, one of the traditional mordants used since antiquity. Household alum that is used for baking is a mordant, albeit a rather expensive one. There are other household ingredients that may be used in natural dyeing such as mild acids (vinegar, lemon juice, cream of tartar) or mild alkalis (baking soda) but these are pH modifiers and not mordants. Some other ingredients such as soy bean milk, or egg whites or blood are used as binders or glues to help adhere pigments to fabric, but these are not mordants as the attachment of the color and the fabric is acting like a glue rather than a chemical bond.