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Engineering Projects


Aim is To dye wool, cotton and silk clothes with malachite green

Dyes are coloured substances which can adhere to the surface of materials and are used to give colour to paper, food- stuffs and various textiles such as cotton, wool, silk, synthetic fibres etc.

The dyed fabrics appear to be coloured because a particular dye absorbs radiations of specific wavelengths from the visible region of electromagnetic radiations which fall on its surface. The remaining radiations are reflected. The colour observed is due to this reflected light.

Characteristics of a dye:

1. It must have a suitable colour.
2. It must be capable of being fixed to the material
3. When fixed it must be fast to detergents, soaps, water, dry-cleaning solvents, light and dilute acids.


500ml beakers, tripod stand, wire gauze, glass rod, spatula, wool cloth, cotton cloth and silk cloth. Sodium carbonate, tannic acid, tartaremetic and malachite green


1. Preparation of sodium carbonate solution.
Take about 0.5g if solid sodium carbonate and dissolve it in 250 ml of water.

2. Preparation of tartaremtic solution.
Take about 0.2g of tartaremetic and dissolve it in 100ml of water by stirring with the help of a glass rod.

3. Preparation of tannic acid solution.
Take 100 ml of water in a beaker and add about 1.0g of tannic acid to it. Heat the solution. On heating a clear solution of tannic acid is obtained.

4. Preparation of dye solution.
Take about 0.1g of malachite green dye and add to it 400 ml of water. On warming a clear solution of the dye results.

5. Dyeing of wool and silk.
Take about 200ml dye solution and dip in it the woollen/ silk cloth to be dyed. Boil the solution for about 2 minutes. After that remove the cloth and wash it with hot water 3-4 times, squeeze and keep it for drying.

6. Dyeing of cotton.
Cotton does not absorb malachite green readily, therefore it requires the use of a mordant. For dyeing a cotton cloth dip it in sodium carbonate solution for about 10 minutes and then rinse with water. Then put the cloth in hot tannic acid solution for about 5 minutes. Now take out the cloth from tannic acid solution and keep it in tartaremetic solution for about 5 minutes. Remove the cloth and squeeze it with the spatula to remove most of the solution. Now place the cloth in boiling solution of the dye for about 2 minutes. Remove and wash the dyed cloth thouroughly with water, squeeze and keep it for drying.

7. Dyeing of cotton directly.
Take another piece of cotton cloth and put it directly into boiling solution of the dye. Keep it dipped for about 2 minutes. Remove the cloth, wash with water, squeeze and keep it for drying


1. The colour of the wool cloth dyed directly by dipping in hot solution of malachite green dye is fast.

2. The colour of cotton cloth dyed directly (without using mordant) by dipping in hot solution of malachite green is not fast to washing and is of low intensity.

3. The colour of cotton cloth dyed by using mordant and then by dipping in hot solution of malachite green is fast to washing and is of high intensity.

4. The colour of the silk cloth is fast and is of high intensity


1. Wool and silk absorb the dye colour well.
2. Use of mordant helps in giving fast colour to the cotton cloth