⚙️ Ferrous Sulphate (Iron Mordant)
Natural Dye Modifier – Deepens Shades & Enhances Tannin Reactions
Ferrous Sulphate, also known as iron mordant, is a traditional and essential tool in the natural dyer’s toolkit. Used in small quantities, this mineral salt modifies color by reacting with tannin-rich dyes to create deeper, cooler shades, such as olive greens, greys, charcoal, and black. It is particularly valued for its ability to shift and darken plant-based colors and improve lightfastness.
Key Features:
100% pure ferrous sulphate 
Acts as a color modifier, especially effective with tannin-rich dyes (e.g. myrobalan, cutch, gallnut, pomegranate)
Creates muted greens, greys, and blacks when used with tannins
Improves light- and washfastness of many natural dyes
Can be used in dye baths, post-mordant dips, or printing pastes
Dyeing Notes:
Often used in post-mordanting to shift colors after dyeing
Reacts with natural tannins to form iron-tannin complexes
Use with caution—iron can weaken protein fibers (like wool and silk) in high concentrations
Ideal for achieving depth, moodiness, and contrast in botanical color palettes
Use 0.5–4% WOF (Weight of Fiber) 
Dissolve in water and use as a modifier bath after dyeing
Alternatively, add small amounts directly to the dye bath for subtle shifts
Always wear gloves and avoid inhalation when handling powders