How could different mordants change the color made by alizarin?

When using alizarin—a dye historically derived from the common madder plant—the final color achieved on a fiber depends significantly on the mordant used during the pretreatment process. These metal salts react with the dye to create different shades.12

The following table summarizes how various mordants alter the color produced by alizarin:

| Mordant | Resulting Color |
| :--- | :--- |
| Aluminum (e.g., aluminum hydroxide) | Red (or Turkey red) |
| Iron (ferrous salts) | Violet or black-violet |
| Chromium | Brownish red |
| Magnesium | Violet |
| Calcium | Purple-red |
| Barium | Blue |

By impregnating fibers like cotton, wool, or silk with these specific metal oxides or salts, craftsmen can manipulate the chemical interaction to produce a wide spectrum of colors from a single dye source.12