MORDANTS for NATURAL DYEING & CONTACT PRINTING

From MIAWA WEBSITE

The Maiwa Guide to Natural Dyes
What they are and how to use them

We've divided the section on Mordants into three parts. We start with some explanations and then describe different mordants, tannins, and other additives. We will give detailed procedures in part three. What follows depends on knowing what fibre you are working with. You may wish to review fibres before reading on.

There are only a few dyes(1) (such as indigo) that can effectively be put on a fibre without first mordanting.

Mordanting the fibre is perhaps the most important step in successful dyeing. It is often rushed or even omitted because no visible change occurs. When we teach natural dyes, we notice that if students can grasp the necessity of good mordanting before they embrace the excitement of colours, then they are well on their way to successful and satisfying results.

Advanced dyers will use the mordanting step itself as a means to influence colour. Mordants can be added through blockprinting or silkscreening techniques, or the application can be controlled through resist techniques. This gives a variety of methods to add pattern to a cloth. Some very subtle effects may be created through control of mordants and tannins.


Mordants facilitate the bonding of the dyestuff to the fibre.There are many mordants and each one will encourage a different shade from a particular dyestuff. As mentioned earlier we do not recommend mordants such as chrome, copper and tin. Although these metallic salts work well to fix the dyes and provide an alternate palette, they are a health hazard and produce toxic waste which requires special disposal. Mordants such as alum, iron, and tannin are safer to use and can produce myriad colours when used in conjunction with the appropriate natural dye. The most frequently used method is premordanting (before dyeing). Occasionally the mordant is added to the dyebath (one-pot dyeing) and sometimes it is added after the dyebath (postmordanting or after-mordanting). Mordant procedures for protein and cellulose fibres are not interchangeable. 

Alum – Potassium aluminum sulfate is the mordant most frequently used by dyers for protein (animal) and cellulose (plant) fibres and fabrics. It improves light and washfastness of all natural dyes and keeps colours clear. It is inexpensive and safe to use (see our safety notes). This form of alum is refined from bauxite, the raw state of aluminum ore, and is free from the impurities (such as iron) some other alums can contain.

 Use at 12-20% WOF. Sometimes we use a combination of two mordants of alum. For example, we will mordant once with alum at 15% WOF and then again with a fresh mordant bath of alum at 15% WOF. Or we will do a tannin/alum/alum mordant to achieve slightly richer colours. 
 

Alum Acetate – Aluminum acetate is sometimes used as the preferred alum mordant for cellulose fibres and fabrics. It is refined from bauxite and acetic acid is used as a purifying agent. For this reason some natural dyes develop to a richer shade on cellulose. Alum acetate is the recommended mordant for printing with natural dyes. It is more expensive and sometimes hard to find.

Use at 5-8% WOF

Homemade Alum Acetate – The dyer may make aluminum acetate from sodium acetate and potassium aluminum sulfate and, depending on the availability of these materials in your area, this can be cost effective.

To make enough aluminum acetate to mordant 1 kilo of fabric, combine in 3 litres of hot tap water:

     150 g sodium acetate 

     150 g potassium aluminum sulfate

 This can be added to your mordant bath. 


Cream of Tartar (cream of tartar)– is the sediment produced in the process of making wine. It is an optional addition to the alum mordant bath and to some dyebaths. It is used to soften wool, brighten shades, and point the colour of some dyes (it will move the fuschia of cochineal to a true red). Cream of tartar works best with animal or protein fibres and is seldom used with plant or cellulose fibres. Use at 5-6% WOF.
 

TANNINS


1 Dyes which do not require mordants are sometimes referred to as substantive dyes. Indigo is the best example of a substantive dye. Occasionally the term substantive will be used for dyes like walnut and myrobalan which are are also tannins. For the natural dyer who wishes the greatest flexibility we recommend that fibres always be properly mordanted.

Natural Dyes - Mordants Part 2

The Maiwa Guide to Natural Dyes
What they are and how to use them

In our previous post we explained why mordanting was necessary and looked at the primary mineral mordant - Alum. We encouraged readers to review fibre types. Now we move on to tannins which are necessary to get fast colours on cellulose fibres such as cotton. Detailed procedures will be described in the next post.

Tannin – Tannic acid is used to mordant cellulose fibres and fabrics before the alum mordant. Alum does not combine as readily with cellulose fibres as it does with protein fibres. Fortunately tannin has a great affinity for cellulose. Once mordanted with tannin, alum will combine well with the tannin-fibre complex. For this reason, the order of a tannin-alum mordant combination is very important. Jim Liles, in his book The Art and Craft of Natural Dyeing presents an interesting historic perspective on the use of tannins on plant fibers - including the belief that it was necessary to "animalize" the fibre. This belief explained some very unusual dye processes.

Many dyestuffs contain tannin (black oakpomegranatecutchfustic, etc) and do not need an additional tannin mordant.

Tannins can be clear or they can add a colour to the fibre. This is a consideration when selecting a tannin. The two most popular tannins in the Maiwa studio are gallnut (oak gall) and myrobalan.

There are three types of tannins.

     • Clear Tannins: “Gallic” - GallnutTara, Sumac
     • Yellow Tannins: “Ellegic” – MyrobalanPomegranateBlack OakFustic
     • Red-Brown Tannins: “Catechic” – CutchQuebracho, Tea leaves


Oak Gall - This is the earliest and richest source for natural tannin and is the clearest of the tannins. It is found in the gallnuts of oak trees. A gallnut is produced by the tree as a defense against insects who deposit their eggs in small punctures they make on young branches. The tree excretes a tannin-rich substance that hardens and forms a gallnut.
 

Gallnuts are collected and ground into a powder that may be used to mordant cloth, in leather tanning, or medicinally.

Use gallnut at 6-8% WOF.

Myrobalan - This dyestuff consists of ground nuts of the Terminalia chebula tree. This tree grows in Nepal, India, Sri Lanka, Burma, Thailand, Indochina and south China. It may be classed as both a mordant and a dye, giving a light buttery yellow when applied.

Myrobalan is an important tannin-based mordant for cotton in India and Southeast Asia due to the light warm colour it imparts to the cloth. The colour works well for overdyeing. Myrobalan is also the perfect colour to lay down under a single indigo dip for teal.
When used as a tannin mordant, myrobalan requires 15-20% WOF. If used to create a soft butter yellow colour 20-30% WOF is needed. 


Iron (Ferrous Sulfate) – This is an optional step. Iron is used as a colour changer. It has the added benefit of making naturally dyed colours more lightfast and washfast. It is more often used with cellulose fibres like cotton, linen, rayon and hemp and should be used with care on protein fibres as it can make them slightly hard or brittle. Iron shifts a colour to a deeper, darker shade. Dyers say it "saddens" the colour. If used in the mordant process that shift is more distinct than when used directly in the dyebath. Iron should be used at 2-4% WOF. More than that could damage the fibre.

 

When printing with natural dyes we recommend changing ferrous sulfate to ferrous acetate to avoid bleeding and ferrous transfer (the migration of iron).

Homemade Ferrous Acetate

5 g ferrous sulfate
100 ml vinegar
3 g lime (calcium hydroxide)

Combine the above ingredients in a plastic container and stir well. If thickening is required, weigh the amount of ferrous acetate you wish to thicken and add 1% of guar gum.
 

Ferrous acetate needs to be fixed. We use chalk (calcium carbonate) 50g in 5 litres of warm water. Once your ferrous acetate is fully dry dip it into this solution. This solution may be kept and reused again and again. Generally you may refresh with 50 g of chalk after each 10 kg of fabric. Full instructions are given in the next post.