In most cases, a mordant, or dye fixative, is needed to make your dye bond with the fibres and become permanent. Mordants can produce shades that are brighter, darker or altogether different from the colour of the plant source. For example, with madder, alum produces a rich Chinese-lacquer red, while chrome yields a garnet red. Iron darkens the colour; tin makes the colour brighter. Consult books or online blogs to find the best mordants to use for your plant material – then experiment! Record your dyeing methods as you go.