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 oak, pomegranate, cutch, fustic, 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” - Gallnut, Tara, Sumac
     • Yellow Tannins: “Ellegic” – Myrobalan, Pomegranate, Black Oak, Fustic
     • Red-Brown Tannins: “Catechic” – Cutch, Quebracho, 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

Sometimes the insect may escape this prison - in which case we see an escape hole in the gallnut. Sometimes the plant wins and the parasite remains in the nut.

The one that didn't make it out. Wasp found inside 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 nuts - the preferred tannin throughout Asia.

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.

India. Myrobalan being used on cotton.

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.

Cambodia. Terracotta pots containing "ironwater" for natural dyeing. The solution is prepared by combining oxidized metal, water, mealy wheat and jaggery (sugars).

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.

Comparison of a dye used alone and with iron.

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.

The Maiwa Guide to Natural Dyes

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