Week 10 - Some Scientific Explanations Behind Natural Dyeing

Are Blueberries Really Blue?

The Science Behind Structural vs. Chemical Color

When you look at a blueberry, it appears unmistakably blue. But if you crush it, you’ll notice the juice isn’t truly blue—it’s more of a deep red or purple. So what’s going on here?

The secret lies in structural color versus chemical color. Chemical color comes from pigments. Molecules that absorb certain wavelengths of light and reflect others. These are the typical colors we think of in dyes or paints. Structural color, on the other hand, is an optical illusion. It’s created when microscopic structures on a surface interfere with light to reflect certain colors. This is how peacock feathers shimmer and soap bubbles show rainbows. Blueberries, it turns out, get much of their blue appearance from light scattering on their waxy skin, not from blue pigments.

How does Iron Water Change the Color of Natural Dyes?

For the past few weeks, I’ve worked with iron water—a blend of rust (iron oxide), water, and white vinegar as a color modifier. But how does it work?

1. Metal-Dye Complex Formation

Iron ions (Fe²⁺ or Fe³⁺) interact with dye molecules to form metal-dye complexes. These complexes absorb and reflect light differently than the dye alone. The result? A visible color shift, often toward darker more neutral tones like gray, blue, black, or purple. 

2. Affecting PH of solution

Iron mordants also slightly acidify the dye bath. Since many natural dyes are pH-sensitive, even a minor pH shift can change the color outcome. For example, the madder root may shift from orange to red depending on the acidity of the solution.

That’s all for my senior project!