Ferrous sulphate, more commonly known as iron, is used as a natural dye modifier, darkening (or 'saddening') natural dyes. It also can act as a mordant, to improve light and wash fastness for dyes,

Ferrous sulphate is considered toxic, keep away from children and pets, work in a ventilated area and wear a mask and gloves whilst handling this powder. I recommend keeping any tools used for this process separate from kitchen tools.

This material comes in a natural biodegradable cellophane. We recommend transferring this to a glass or plastic jar for long-term storage.