Tie Dye Chemistry

What Makes Fiber Reactive Dyes Work?

The group of atoms and electrons in a molecule that produces color in dyes and other compounds through selective absorption of light is called a “chromophore”.

Through a chemical reaction called covalent (electron-sharing) bonding, fiber reactive dyes attach permanently to the cellulose fiber molecule’s chomophores. Covalent bonding is the one of the most basic and strongest types of chemical reactions. It happens over time depending on temperature and/or the Ph level where it the process occurs.

The Soda Ash pre-soak raises the pH level of the garment or fabric to approximately 10.5. Raising the pH level of the solution that the fabric or garment is soaked in raises the level of negative hydrogen ions in the dyeing environment. The chemical bonding process uses these ions in the reaction. Pre-soaking in Soda Ash fixer solution is what allows the fiber reactive dyes to work at room temperature. The reaction can also be aided with heat.

The dyed garment is allowed to react in a desirable environment for up to 24 hours. After this time, the bonding sites on the cellulose should be saturated with dye molecules. Excess dye molecules that have not bonded permanently are washed away using warm water rinse and a detergent.

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