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  Dyeing fibres using locally grown plants

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Mordanting wool before dyeing, How and Why?


Shetland sheep are small hardy animals. The wool is soft and full of lanolin making the fleece water repellent. Hill sheep are also living in peat conditions so the fleece is often dirty. It is essential to clean the fleece thoroughly before attempting to dye the wool. Soak it in hand warm soapy water overnight, rinsing and repeating as many times as needed until the fleece is clean. Then a mordant needs to be used to enable the fleece to absorb the dye pigment..

The fibres of wool that make up a fleece do not absorb pigment from plant dyes. Dyeing without first mordanting the fibre leaves the pigment on the surface of the fibres. This is not lightfast and will easily wash out. There are a few plant dyes that contain a natural mordant, these are known as substantive dyes and the pigment will be absorbed by the fibre and so no mordant is required.

Once a mordant has been applied it is absorbed by the fibres and then, when dyed, the mordant in the fibres takes in the dye pigment.

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Alum is a commonly used mordant. It can be purchased as crystals or powder from some chemists. Alternatively it can be found online at various suppliers of natural dye materials. It is easily used and gives many plant dyes a vibrant hue that is both light and wash fast.

rhubarb leaves

A natural mordant, easily available, is to use rhubarb leaves. They are high in oxalic acid which provides the fibres with the mordant required to absorb plant dye pigment. Oxalic acid is poisonous if consumed so care needs to be taken when preparing.

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Sometimes a mordant can be used during or after the dyeing process. A dye colour can be altered or 'shifted' when an after mordant is used. Iron is a good example, it will turn yellow dye baths into green when used carefully. Iron mordant can be made easily by placing rusty nails into a jar filled with half white vinegar, half water. In a week or so the orangy liquid can be used as an iron mordant.

Mordant Recipes


1.5 teaspoons Alum per 100gms wool with 1 teaspoon Cream of Tartar per 100gms wool

Put Alum in stainless steel bowl, add enough hot water to dissolve. Stir this into a saucepan of cold water

with enough room to agitate wool freely.  Add the Cream of Tartar by dissolving ina little hot water, add this

to the saucepan. Now place the wool into the water and heat slowly until a light simmer is achieved.

Hold this temperature for about 45 minutes gently turning the wool from time to time. Leave to cool and

rinse the wool. It is now ready for dyeing.


Rhubarb Leaves:

Pick enough Rhubarb leaves to tear and fill a saucepan. Add cold water and slowly bring to simmer. it

may be necessary to top up the water as the leaves shrink down. Leave to simmer with a window

open for about 45 minutes. Remove from heat and cool. Strain the liquid when cold and then add

the wetted fibres. I use a gallon pan and add about 250 gms of wool. reheat to simmer and keep the

temperature for another 45 minutes or so. Cool and then the wool is ready to dye.


Iron After Mordant:

Prepare the iron mordant as described above. Once the initial dyeing has been completed  lift out the fibres          

add halff a teaspoon of the iron mordant liquid to the dye vat. Stir and the colour will shift quickly.

Replace the fibres and they will take up the altered colour. More iron can be added to darken the shade.

Once completed cool and rinse very well to prevent the iron from causing the fibres to become brittle.