Ferrous Sulphate (Iron) Mordant
Ferrous Sulphate (Iron) Mordant
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Ferrous sulphate (iron) is a powerful mordant and colour modifier used in natural dyeing to deepen tones and create rich, muted shades. Known for its ability to “sadden” colours, iron shifts brighter hues into earthy greys, olives, and deep browns, making it an essential tool for natural dyers seeking more complex, tonal results. It is commonly used with tannin-rich plant dyes and works effectively on both protein fibres like wool and silk, and cellulose fibres such as cotton.
Iron should be used carefully and in small quantities, a little goes a long way, it can also make fibres feel harsher if overused.
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Ferrous Sulphate (Iron) Mordant
What is ferrous sulphate (iron) used for in natural dyeing?
Ferrous sulphate (iron) is used to darken and mute colours, shifting bright plant dyes into more subdued, earthy tones. Yellows can be modified to greens, and reds become purples.
Is ferrous sulphate (iron) a primary mordant?
Iron is more commonly used as a modifier to adjust colour, though as a mordant it does improve washfastness.
Which fibres can be used with ferrous sulphate (iron)?
It works on both protein and cellulose fibres such as cotton, though care is needed with wool to avoid fibre damage.
Safety guidelines
- Wear protective gear - gloves, an apron or old clothing, a dusk mask when handling powders.
- Dedicated equipment - keep tools separate from your kitchen items. Use stainless steel or enamel to prevent reactions or colour modification.
- Ensure the space you’re working is well ventilated.
- Handle mordants and plant dyes with care.
- Dye baths involve hot water, be mindful of burns or spills.
- Dispose of materials responsibly.
We cannot guarantee exact colour results with our natural dye products. Each batch is naturally unique, contributing to the distinctive, handcrafted character of your finished pieces. For best results, we encourage experimentation, as colour outcomes can vary depending on fibre type, mordant used, and water quality.