Dyeing

Question 1

What is dye affinity? How is created?

Answer 1

Affinity is how easily the chemicals in fibres and the chemicals in dye bond.

It is created using a mordant, which also improves colourfastness.

Question 2

At what stages can dyeing occur?

Answer 2

1. The fibre stage.
2. The yarn stage.
3. The fabric stage.
4. The garment stage.

Question 3

What is dope dyeing?

Answer 3

Dyeing synthetic fibres whilst they are still liquid, before they are spun.

Question 4

What is stock dyeing?

Answer 4

Dyeing natural fibres in dye baths.

Question 5

Why is dyeing at the yarn stage expensive? Why is it not as good as fibre dyeing?

Answer 5

The yarns have to be wound up in a special way before they are dyed to prevent them tangling.

The dye is not distributed as evenly using this technique, compared to fibre dyeing.

Question 6

What is piece dyeing?

Answer 6

Dyeing at the fabric stage.

Question 7

Why is piece dyeing cost-effective?

Answer 7

Fabric can be stored un-dyed, then only dyed when needed.

Question 8

Why is dyeing at the garment stage unusual?

Answer 8

Areas such a seams may be affected differently by the dye, compared to the rest of the garment.

Question 9

What are the environmental issues associated with dyeing?

Answer 9

1. Large amounts of water are needed.
2. Waste from dyes can be toxic when released into the environment.
3. Dye is not biodegradable.

Question 10

What are the benefits of synthetic dyes?

Answer 10

1. They produce string, vibrant colours.
2. They are easy and cheap to produce.
3. The produce a constant colour each time.
4. A huge variety of colours can be made.

Question 11

What are the five main types of dye?

Answer 11

1. Direct dyes.
2. Reactive dyes.
3. Vat dyes.
4. Disperse dyes.
5. Acid dyes.

Question 12

What are the properties of direct dye? What fibres should it be used on?

Answer 12

Direct dye is water soluble and therefore had poor wash fastness.

It is used on cellulose fibres.

Question 13

What are the properties of reactive dye? What fibres should it be used on?

Answer 13

Reactive dye has good wash fastness and creates strong colours.

It is used on cellulose fibres, protein fibres, and nylon.

Question 14

What are the properties of vat dye? What fibres should it be used on?

Answer 14

It is not water soluble and has to be made soluble by removing the oxygen from it. It sits on top of a fibre rather than being absorbed.

It is used on cellulose fibres.

Question 15

What are the properties of disperse dye? What fibres should it be used on?

Answer 15

Disperse dye is insoluble in water.

It is used to dye hydrophobic fibres like acetate, polyamide, acrylic, and polyester.

Question 16

What are the properties of acid dye? What fibres should it be used on?

Answer 16

Acid dye is water soluble and applied using a dye bath.

It is used to dye protein fibres and polyamide.

Question 17

What does a fabric need to be colourfast to?

Answer 17

1. Bleach.
2. Dry cleaning.
3. Washing.
4. Light.
5. Perspiration.
6. Friction.

Question 18

What is the preparation process for dyeing?

Answer 18

1. Desizing - Washing out the starch that was applied to the yarns to strengthen them before weaving.
2. Scouring - Removes waxy and fatty impurities which would resist dye from natural fibres.
3. Bleaching - Makes the fabric an even shade of white before dyeing.