Helo, reders today i m going to explain about natural dyes, classification, mordant, uses and more.
If you know about natural dyes in details then this article is best for you.
I have made valuable information out of it.
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What is natural dyes
Natural dyes are made those colours, dyes and pigment that are obtained from animal or vegetable without chemical processing.
Sources of natural dyes
- Plant and animal sources;
Many plants and some animals are potentially rich in natural dye content. Dyes are made with the help of various part of plant such as, stems, leaves, fruits and seed contains colouring matter. Depth of shade of dyes are vary because it is depand upon time of year.
2. By product (lac dye)
The lac industry produce lac dye as a by product which is extracted from effluent.
3. Attempt has also been made to synthesize natural dye having similar structure.
4. Genetic modification of certain fungi have produced Anthraquinone dye.
Classification of natural dyes
They are classified by various ways;
• Substantive dye: the dyes which can dye the fibre directly without mordant such as; turmeric dyeing.
• Adjective dye: these dyes colour the material which is mordanted with metallic salt such as, logwood.
2. Monogenetic and polygenetic natural dyes.
• monogenetic: it is produce only one type colour irrespective of mordant persent in the fiber.
• polygenetic: it is produce different types of colours but it is depand upon mordant.
3. Soluble and insoluble natural dyes
• Soluble: they can easily dissolved and then it is applied on textile materials.
• Insoluble: they have not solubilizing group hence temporary solubilizing group is introduce such as, Indigo.
Classification of natural dyes on the basis of chemical structure:
Classification of mordant;
- Metallic mordant:
Metal salt of aluminium, iron, copper chromium and tin are windly used.
2. Tannins/ tannic acid:
It has no natural impurities and used for dyeing for light shades. after dyeing it produce light shade on textile goods.
3. Oil Mordant
They are mainly used in dyeing of red colour from madder. it is also known as wood or rubia. however alum has to be used as main mordant to dye this colour along with oil mordant.
Application of Mordants:
- Alum mordant:
• If you add alkali + alum solution produces aluminium sulphate which is used as mordant.
• if you make solution of 1kg of alum + 0.5 kg NaOH + 200 liter water. It can be used to mordant 10kg of cotton by direct impregnation.
• it is not suitable for silk materials because it reduces luster.
2. Copper mordant:
CuSO4 is fixed with the help of tannin/ tannic acid.
3. Iron Mordant
• Mostly used for dyeing black.
• These mordant are applied on tannic treated cotton fabric, which forms ferrous tannet.
• Application is done by padding two times and followed by air oxidation.
• It is generally used for silk materials for dark shade.
Dyeing of cotton with Marigold flower
- Dyeing at 80°C for 1-2 hours.
- Soap with 2gpl non-ionic soap with room temperature.
- This dyeing process has no side effects on skin.
- It is cheap process
- Colour obtained: golden yellow
- Colour fastness: 3-4
- It contain Flavanol
Maximum extraction is done at below given conditions;
• Mild basic medium
• 3 hours.
Mordant which can be used are Alum, copper sulphate, ferrous sulphate.
Limitation of natural dyes
• it required long time for dyeing.
• it give poor reproducibility.
• High production cost.
• it is Costly process.
• low colour yield.
• Some metallic mordant are hazardous.