Mordants are used alongside natural dyes to make colours lightfast and washfast, as well as enhance or dull colour results. Experimenting with mordants and after baths is a great way to increase the spectrum of colours in your palette.
Mordanting can be done before (premordanting),during dyeing (simultaneous mordanting), or after dyeing (after bath).
Here are a list of common mordants:
Alum – Aluminum Potassium Sulphate - Brightening Mordant
USE AT 15% WOF
A white powder or crystal that accentuates yellow tones. Pickling alum or
Ammonium Potassium Sulphate is a non-poisonous substitute. Alum is
commonly used in conjunction with Cream of Tartar.
Tin – Stannous Chloride - Brightening Mordant
USE AT 1% WOF
A white crystal that enhances gold, red and orange. Because it ‘hardens’ the wool, it should always be given soapy rinses.
Copper – Cupric Sulphate – Dulling Mordant
USE AT 2% WOF
A blue crystal, also called vitriol, that enhances greens and browns.
Iron – Ferrous Sulphate - Dulling Mordant
USE AT 2% WOF
A green crystal, also called green vitriol or copperas that accentuates greys or tans. Performs well as an after-bath over alum/copper. Rust water can be used as an alternative to iron. You can make rust water by soaking rusty objects (such as nails or an old bike chain) in 1 part vinegar, 1 part water.
Dye additives are often used in combination with mordants, or as part of after baths:
Cream of Tartar – Potassium Bitartrate. USE AT 5% WOF WITH ALUM- A white powder that adds brightness and buffers the harshness of mordants.
Vinegar – Acetic Acid: Is used to soften hard water, to brighten colours, and, to neutralize an alkaline bath. LOWER PH LEVEL TO 4 MINIIMUM
Salt – Sodium Chloride: Any form of cooking salt can be used to soften colours and to slow the rate of colour absorption.
Thiourea Dioxide (Spectralite): A reducing agent used in Indigo dyeing and an excellent substitution for sodium hydrosulfite in color stripping and discharge. It is safer to use, has a greater strength, and does not lose its strength over time. It can be used for stripping cellulose fibre or bleaching wool or silk.
TNA Soap: A clear liquid soap for washing when using dyes, which is non-ionic and pH neutral. This soap also helps prevent staining of white or light areas during the wash-off procedure. (other brands: Synthrapol, Texascour)
Sodium Carbonate (Soda Ash): Used to develop and set a dyebath, increase pH, changes colour of some nature dyes towards reds/purples, neutralize an acidic dyebath RAISE PH TO 10 MAXIMUM. Common baking soda (sodium bicarbonate) is very similar but much weaker
MORDANT PROCESS FLOW CHART
-Notes and flow chart provided by Laurie Wassink (Instructor), MAAD 2B38, Fibre: Dyeing, OCAD University