Learn to use mordants: dyeing's secret ingredient

Mordants are chemicals that help keep dyes from fading or washing out. We'll teach you how to use mordants effectively and safely on all kinds of fabric and textiles.

Before you start, keep in mind that mordants are strong, poisonous chemicals. Be sure to handle them carefully and always keep them beyond the reach of children. Use them in a well ventilated place, and keep the mordanting pot covered to prevent chemicals from escaping into the air. Never use mordant containers to prepare or cook food.

• Textiles may be mordanted either before or after dyeing, or you can add the mordant directly to the dyebath. It's simplest to do the mordanting first.
• Once the fibres are mordanted, you can soak them in a dyebath for as long as necessary to achieve the desired shade.
• Use an enamel or stainless steel pot for cooking and a wooden rod or spoon for stirring. Dissolve the chemical in about 8 litres (8 1/2 quarts) of lukewarm soft water (use commercial water softener if necessary). Then thoroughly pre-wet the textile and immerse it in the mixture. Slowly bring the bath to a simmer or boil. Once the yarn has been mordanted, it may either be dyed immediately or dried and saved for future use.

Mordants are sold by most pharmacies and chemical supply houses and are available in a range of purities. Chemical grade mordant is less expensive than purer grades and is sufficient for dyeing purposes. The most common and effective mordants are alum, blue vitriol, chrome, copper, tannic acid, and tin. Here are the characteristics of each:

• Alum (potassium aluminium sulphate) causes the least change in colour. Use one tablespoon (15 grams) per two litres (two quarts) of water and simmer for one hour to mordant wool, silk, or other animal fibres. For cotton or linen use 20 grams of the mordant per two litres (two quarts) of water and boil the fibres for one hour.
• Copper (copper sulphate) sometimes colours fibres green. Use three millilitres (1/2 teaspoon) per two litres (two quarts) of water and simmer for one hour to mordant animal fibres. For cotton and linen use 15 millilitres (one tablespoon) per two litres (two quarts) of water and simmer for one to two hours.
• Chrome (potassium dichromate) often strengthens colours. Use two millilitres (1/4 teaspoon) per two litres (two quarts) of water for animal fibres and simmer for one hour. With linen or cotton use seven millilitres (1 1/2 teaspoom) per two litres (two quarts) of water and boil for one hour. Chrome mordanted fibres are turned brown by exposure to light, so keep the mordant pot covered and dye the yarns immediately (or store them in complete darkness). Keep the pot covered when dyeing the chrome mordanted fibre.
• Iron (ferrous sulphate) tends to grey colours. For wool, use two millilitres (1/2 teaspoon) per two litres (two quarts) of water and simmer for 30 minutes. For linen or cotton use 15 millilitres (one tablespoon) per two litres (two quarts) and boil for one hour.
• Tin (stannous chloride) will brighten colours (especially reds and yellows), but it can easily damage fibres. To prevent damage, mordant the fibres for as short a time as possible and wash them thoroughly after mordanting. For both animal and plant fibres use 15 millilitres (one tablespoon) per two litres (two quarts) of water and simmer for one hour. Some dyers use tin in combination with some other mordant by adding one millilitre (1/4 teaspoon) of tin to eight litres (8 1/2 quarts) of dyebath for the last few minutes of dyeing. Remove the fibres, add the tin to the solution, and then replace the fibres.

Follow these tips closely and always use the proper safety precautions when working with mordants. When used properly, you'll have long-lasting fabrics and textiles that are truly to dye for.