Dyeing fabrics 0.0 / 5 ? TextilesTextilesA2/A-levelAQA Created by: Steff06Created on: 08-06-16 21:28 Describe direct dyes Soluble in water, moderately fast to light but have poor wash fastness. 1 of 24 What can be added to help the fabric absorb the dye? A mordant such as salt. 2 of 24 What fibres can direct dyes be used on? Cellulosic fibres and regenerated e.g. cotton, viscose, modal. 3 of 24 Describe reactive dyes Water soluble which give bright colours and are fast to washing. 4 of 24 What fibres can reactive dyes be used on and how? Forms strong chemical bond with cellulosic and protein fibres e.g silk, wool, cashmere, linen. 5 of 24 Describe vat dyes Not soluble in water. Excellent wash and light fastness. 6 of 24 What is one of the best known vat dyes? Indigo, which dyes denim blue. 7 of 24 How does the vat dye get into the fibre? Converted into a soluble form by removing oxygen. 8 of 24 What happens once the dye is in the fibre? It is converted back into its insoluble form by oxidation, making molecules too big to get out. 9 of 24 What causes indigo dye to rub off onto other fabrics and lose colour when washed? Indigo dye sits on top of the fibre rather than being absorbed into it. 10 of 24 What fibres are vat dyes used on? Cellulosic, regenerated, linen and ramie. 11 of 24 Describe disperse dyes Almost insoluble in water and applied in the form of a fine aqueous dispersion. Held inside fibres by chemical bonds. 12 of 24 What fibres are disperse dyes used to dye? Fibres with hydrophobic properties such as acetate, polyamide, acrylic and polyester. 13 of 24 Describe acid dyes Soluble in water. Good fastness to light but wash fastness varies. 14 of 24 How are acid dyes applied to the fabrics? In an acidic dye bath. 15 of 24 What fibres are acid dyes used to dye? Protein fibres, polyamide. 16 of 24 Describe how solvent dyes are applied to fabric Applied using organic solvents instead of water. 17 of 24 Why is using solvent dyes expensive? Disposing of it after and water usage is expensive in a non-polluting way. Cost involved in recovering organic solvent. 18 of 24 When can mordants be applied? Applied in dye bath, before dyeing or after dyeing. 19 of 24 What must be considered when selecting a dye to use for a fabric? Colour requirements, fastness requirements, cost. 20 of 24 When are dyes with poor properties used? When they are the only ones available that will produce a particular shade wanted by customer demand. 21 of 24 Describe the 3 steps in the process of dyeing Immersing the textiles in the dyebath, dye attaching itself to the fibre, fixing the dye e.g. with a mordant. 22 of 24 What does the strength with which the dye is held in the fibre dependent on? Depends on physical forces resulting from shape of the dye molecule, structure of the fibre and chemical forces present. 23 of 24 What is the strength with which the dye is retained within the fibre related to? Related to property of washing fastness. 24 of 24
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