Mordanting & Dyeing silk
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Mordanting and Dyeing Silk

B. How to mordant silk

Make sure the silk is very clean first. Keep the temperature below 85º C when mordanting and dyeing, to avoid damaging the lustre of the silk.
It is important to use a stainless steel spoon when handling the silk, as silk fibres can catch on the edge of a wooden spoon.

You can use either alum or aluminium lactate or aluminium acetate as the mordant. Use 25% alum or 8% aluminium lactate or aluminium acetate per weight of dry silk. I prefer to use alum for pure silk and for wool/silk blends. However, for cotton/silk blends as well as hemp/silk blends, aluminium lactate or aluminium acetate is better. For these types of blends, use 8% aluminium lactate or aluminium acetate per dry weight of goods. Use a face mask when using aluminium acetate, as it is a very fine powder.

If you are dyeing the silk with woad or indigo, you do not need to mordant the silk first.

You will need:
• 100 grams of silk
• 25 grams alum (or 8 grams of aluminium lactate or aluminium acetate)
• large stainless steel spoon
• saucepan (10 litres or larger)
• rubber gloves

1. Weigh the silk, using no more than 100 grams of silk for a 10 litre saucepan.

2. Fill a bowl with hot tap water and add a drop of washing up liquid. Place the silk gently in the bowl and leave it to soak. Do not crowd the silk, but leave plenty of space around it allowing a bit of room for expansion. It takes time to get silk thoroughly wet and it is better to leave it to soak overnight.

[If using mawata caps (silk hankies) divide a 100 gram bundle of hankies in half to make two bundles of about 50 grams each. The hankies should look translucent when wet. The mordant will not penetrate properly if the hankies have dry spots (which look white).]

3. Weigh the alum, using 25% of the weight of dry silk (i.e. for 100g of silk use 25 grams of alum).

4. Place the alum in a small heat proof container and pour boiling water into the container. Stir it well until the alum has dissolved.
5. Fill a 10 litre saucepan ¾ full with hot tap water, add the dissolved alum and stir well.

6. Add the pre-soaked fibres. Wearing rubber gloves, work the silk gently into the mordant for a few minutes.

7. Leave the silk in the pot for 24 hours without adding any heat and stir gently and occasionally.

8. At the end of the 24 hours take the silk from the pot. You can either rinse it gently and then dye it, or leave it to dry and dye later.

C. Dyeing silk with natural dyes

1. Soak the mordanted silk in warm water overnight or for at least two hours.

2. You will find it easier to dye silk using natural dye extracts, which are concentrated and faster to use.

For bright colours, try the following quantities of extract per 100 grams of silk
-5 grams of brazilwood, lac, logwood, chlorophyllin or cochineal
-20 grams of madder, coreopsis, weld, Persian berries, greenweed or goldenrod
-50 grams of cutch

3. Mix the chosen extract into a paste with a small amount of hot water. Fill a saucepan with hot water and add the mixed extract. [Add 1/3 teaspoon of chalk if you are using weld or madder.]

4. Add the wet mordanted silk and leave overnight. Stir from time to time using a stainless steel spoon.

If you want to overdye your silk with a second natural dye, mordant it again before overdyeing it. You can use 15 grams of alum per 100 grams of silk when you are mordanting the silk for the second time.

D. Advanced silk hanky dyeing [coming soon]

E. Silk painting with natural dyes extracts [coming soon]

And back to:-
Choosing which type of silk to dye (previous page)

Mordanting Wool and Cotton etc

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Updated on 19 April 2021
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