Black cardboard box with a bright yellow design containing neon fabric dye. Dye instructions are printed in white on the back of the box. The powdered dye is contained in a paper packet. Dye instructions are also printed on the packet. The packet is stained yellow due to the dye inside.

Fabric dyes are charged, water-soluble, organic compounds that chemically bind with fabric. The affinity of the dye for the fabric depends on the molecules and the interactions between them. To improve the binding affinity, an additive called a mordant may be added to the solution. A mordant contains metallic salts, which provide a connection between the dye and fabric molecules.