Making an iron mordant (also known as iron sulfate or ferrous sulfate) at home is a process used in natural dyeing to help bind dye to fabric.
The method is quite simple.
that requires careful handling and preparation, as iron can be toxic in high concentrations. The iron mordant is particularly useful for shifting dye colors to darker or more muted shades and can be used on a variety of fibers. Here’s a simple way to make an iron mordant using steel wool and vinegar, a method that is relatively safe and easy to do at home.