Concentrated Acid Dyes

Acid dyes provide a simple system for use with wool, animal fibres and nylon, and give a brighter colour with silk than Procion MX Fibre Reactive Dyes. They can be used to dye fur, feathers, soya bean fibre, angora, cashmere but are not effective on synthetics, other than nylon. There are a range of names, both historic and current for these dyes, but they are now commonly known simply as the 'Acid Dyes', which is somewhat inappropriate as they do not contain acid.

They can be used effectively from a stock solution for painting on silk and set with steam (see how). This sample of painting on silk was created by Linda Chapman using silk paints which are very effective for this technique. Iron-fix silk paints are made from tiny particles of pigment which sit on the surface of the silk. Dyes, however, penetrate the fibres of the silk and retain the suppleness and reflective qualities of the silk fabric.

Safety

There is no substantiated evidence of a causal link between exposure to acid dyes and any chronic or fatal illnesses. Both the acid and fibre reactive dye families have a considerable track record, of use in industry in considerable quantities and in a less well controlled environment in the crafts

It is clear that there are sensible precautions to be taken when handling dyes and chemicals, particularly as powders:

• Avoid inhaling dusts, they can produce an asthma type reaction. People with known respiratory problems should not handle synthetic dyes, and particularly the fibre reactive dyes, in powder form. A dust mask should be worn when working with the powders or exposed to an aerosol from spraying dye solutions made up in water
• Avoid splashing solutions into the eyes, swallowing the materials or prolonged skin contact. A simple 'non-contact' approach (most people use gloves to avoid dyeing themselves) plus normal, good, hygiene is sufficient precautions for the occasional user
• Store in clearly labelled containers well away from children, pets and foodstuffs. Treat dye powders and solutions with the same caution as domestic poisons (e.g. strong cleaners, bleaches or medicines)
• Dispose of spent solutions containing residues of the dyes responsibly. Dilute and pour onto waste land or into the sewage system. They have no known effect on the environment when used in the quantities recommended in the literature

Making a Stock Solution

It helps to prepare a stock solution of these dyes to a known strength per litre. Some dyes are fairly difficult to get into solution and may form a tar like ball first. The stock solution of Acid dyes has a shelf life of around six months. The Acid dye powder does not always dissolve fully in the cold, or may precipitate on cooling or when left to stand. Always stir the stock dye solution well before use since some sedimentation may occur. Over time a mould may form on the surface, skim it off, and heat the dye stock to boiling to kill the spores, the dye will not be affected.

Typically, the quantities of Acid dye used, including black, range from 0.25gm to 2.0gm for each 100gm of dry material. These quantities will create colours ranging from pale to deeper shades.

1. The dye is in powder form. It is easier to measure small quantities of solutions than of powders - particularly if you use syringes. Make up the powder into a stock solution - 1% is a convenient level (i.e. 5gm in ½ litre of water).
2. Mix the Acid dye powder to a paste first in a small amount of warm water or methylated spirit, then dissolve thoroughly in boiling water. Top up to the chosen volume when cold.
3. Before dyeing, it is important to check whether the fabric is 'Prepared for Dyeing' (PFD) or requires scouring to remove any grease, oil or starch. Run a few droplets of cold water onto the fabric. If they soak in quickly, no scour is necessary. To remove starches, size and oils, add 5mls of Synthrapol (a non-ionic detergent) along with 2-3 litres of water for each 100gms of material. Stir gently over a 15 min period, and then rinse thoroughly in warm water. It is possible to use household detergent, but the alkaline residue may affect the final colour or wash fastness.

Dye Bath Technique for Acid Dyes:

1. The dye bath must be heat proof, of glass, enamel or stainless steel (do not use cooking pots). The quantity of water is not critical except that for even results there must be plenty of room for circulation. A typical volume (liquor ratio) is 30 times as much water as fibre i.e. 750ml water for 25g fibre (1.5 pints for 1oz).
2. Weigh the dry fibre or yarn. Degrease it thoroughly by scouring with hot detergent solution and rinse well. Commercial yarn or fabric often picks up oil during processing or is 'starched' - either will prevent the dye reaching the fibre.
3. Measure warm water into the dye bath to give about 30:1 on fibre weight. Add Glaubers salt at a ratio of 10gm per 100gm fibre (this is convenient made up as a stock solution at 10% concentration - 50gm in ½ litre or 2oz in 1 pint). Use 25ml for 25gm fibre.
4. Add 25ml white vinegar for each 25gm fibre and stir well.
5. Submerge dampened yarn/fibre in the bath and soak for 10 minutes. Remove it and then add the dye solution and stir well. Return the yarn/fibre and gently move around the bath for 10 minutes.
6. Heat the bath to hand hot. Remove from heat and allow to stand for 10 minutes. Stir and return to heat. Maintain at a simmer just on boiling for 20 minutes but DO NOT STIR or allow to boil fast enough to cause movement (and hence felting).
7. Allow to cool without stirring and rinse well.
8. Stir well in the early stages while cool but only a little and very gently while hot - or felting will occur. It is essential to boil to achieve good fixing of dye to fibre and hence wash fastness.
9. Use only half the quantity of vinegar when dyeing synthetics.

When dyeing larger quantities of materials the vinegar cost can become significant, in this case concentrated acetic acid from a photographic suppliers is a more economic solution.

Before dyeing, it is important to check whether the item is 'Prepared for Dyeing' (PFD) or requires scouring to remove any grease, oil or starch. Run a few droplets of cold water onto the fabric. If they soak in quickly, no scour is necessary. To remove starches, size and oils, add 5mls of Synthrapol (a non-ionic detergent) along with 2-3 litres of water for each 100gms of material. Stir gently over a 15 min period, and then rinse thoroughly in warm water. It is possible to use household detergent, but the alkaline residue may affect the final colour or wash fastness.

Quick Microwave Method for Acid Dyes:

This is a quick and satisfying technique for creating 'space dyed' yarns, fibres and fabrics using Acid dyes. The silk fibres for this hand spun yarn by Susan Litton were dyed with Jacquard Acid dyes, using the recipe below:

1. Mix 2 teaspoons of white (distilled) vinegar to 1 litre of tap water and soak the material thoroughly.
2. Line a microwave dish with sufficient cling film to be able to close over the top.
3. Squeeze out and spread the material randomly across the dish.
4. Lightly sprinkle the dye powder onto the surface of the material. A number of colours can be used to create a varied result. The more you add, the denser the result of the colour.
5. Dampen with a small amount of hot water and work the Acid dye powder into the fibres.
6. Fold the cling film over the dish and ensure it is air tight. Place in the microwave
7. Heat on high until the parcel 'inflates' and then reduce the heat to 'defrost'
8. Cook until the parcel begins to billow up again, turn off and leave to cool
9. Rinse several times and put out to dry!

see also:

Jacquard Acid Dyes are premixed acid dye colours and can be applied using the above techniques.

Discharge Acid Dyes are dyes that can easily be removed from fabric using discharge paste. The discharge paste can be combined with Illuminating Acid Dyes which makes for a varied and unusual printing technique. The image shows discharge printing on dischargeable black velvet.

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