colorfastener
nounUK /ˈkʌləˌfɑːsənə/
US /ˈkʌlərˌfæsənər/
A colorfastener is something that keeps colors from washing out.
The shirt stayed bright because of the colorfastener used in the dye.
OTHER MEANINGS
2. A substance added to dye so the color sticks to cloth.
The factory added a colorfastener to the blue dye.
3. A person or machine that makes colors permanent in materials.
The colorfastener checked each batch of fabric.
4. A chemical treatment that stops colors from fading in sunlight.
Curtains are often treated with a colorfastener.