Mordant - Ferrous Sulphate

Iron Sulphate, also known as Ferrous Sulphate, is a traditional mordant and colour modifier used in natural dyeing to darken and shift colours. Often referred to as a way to “sadden” colours, it transforms bright shades into deeper greys, soft blacks and muted earthy tones.

Used either during or after dyeing, iron can significantly alter the final colour, adding depth, contrast and a more aged or rustic appearance. It can also help improve lightfastness in some natural dyes, making it a valuable addition to the dyeing process. This finely milled powder dissolves easily in water, ensuring consistent and reliable results across a range of dyeing techniques. While suitable for use on all natural fibres, it should be used with care on protein fibres such as wool and silk, as overuse can lead to a harsher handle.

Benefits

• Darkens and modifies natural dye colours
• Produces greys, blacks and muted earthy tones
• Enhances depth and character in dyed fibres
• Can improve lightfastness in some dye processes
• Finely milled for easy dissolving and consistent results

Perfect For

• Over-dyeing and natural colour modification
• Wool, silk, cotton and linen projects needing muted tones
• Textile studios, artisans and botanical dye workshops

Technical

• Pure ferrous sulphate mordant for colour deepening
• Enhances wash and lightfastness of natural dyes
• Produces greys, charcoals, and aged tones
• Use 1–2% of fabric weight for post-mordant or modifier baths
• Wear gloves and avoid metal contact with solution