Dye Classes by Fibre: Which Dye Belongs on Which Fabric

A colour only holds if the dye chemistry matches the fibre. Choose the wrong class and you get poor fastness no matter how good the shade looked in the lab - the classic cause of a top that bleeds or fades on the first wash. A designer doesn't need to be a dye chemist, but knowing which class goes on which fibre explains why some colours last and others don't.

Dyes are chosen by fibre, not by colour

Every dye class is engineered to bond to a particular fibre chemistry. Cotton and other cellulosics take one family; polyester needs a completely different one; wool, silk and nylon another. Put simply: the fibre decides the dye class, and the dye class largely decides the fastness. That is why a blend (say poly-cotton) often needs two dyeings - one class for each fibre - to colour fully.