NATURAL PIGMENT DYES Natural Inorganic Pigments are extracted from the earth bed and are available in natural form like ochers, umbers etc. The different kinds of Natural Inorganic Pigments are: * Azurite *
Actually these kind of natural inorganic pigments are copper carbonates having greenish blue shading. From a very long period, azurite has been using as a pigment. But, often these pigments have been replaced by synthetic pigments or used to paint the expensive ultramarine as under paintings.
* Red earths *
These pigments are the most diverse kind of natural inorganic pigments. These are made from clays and they have a large amount of iron oxide. The color varies from dull yellow to dull deep yellow or from dull orange to dull red or from dull dark brown to dark brown.
*.Yellow earths- These are natural earth containing silica and clay. These pigments are present in hydrous form of iron oxide. These pigments also contain gypsum or manganese carbonate. In all over the world, these pigments are available and have been using from the prehistoric period. Synthetic Inorganic Pigments Synthetic inorganic pigments are manufactured in the laboratory. These pigments consists of metallic compounds like manganese violet, cobalt blue. As these pigments are manufactured in the laboratory, so they are found in pure form having fine particles. Synthetic inorganic pigments can also be produced by the replication of the natural earth colors like Mars Red or Yellow. Natural Pigments Naturally occurring pigments such as Cochineal, Aeppo galls, Annatto, Indigo, Ochres and Iron Oxides are known as Natural Pigments. These pigments have been used as colorants since prehistoric times. These pigments are obtained from insects and plants and used in cosmetics. They have affinity to all such foods and drugs which require color additives.
Natural pigments are good for use in the shower gel, bath bombs, bath salts, shampoo, soap, lotion and in many more other products. These pigments have good quality of bleed protectiveness in soap and these are also water dispersible. But, these pigments don't have high intensity in light. Anthocyanin Pigments- Anthocyanin pigments are colored pigments and these are found profusely in plant kingdom. The colors imparted by these pigments are blue, red and purple. The color of fruits and flowers are also due to the color impartation of these pigments. Anthocyanins are soluble in water and their extraction from the plant parts is also easy. Slightly acid mixed water is required for the extraction of these pigments. Carotenoid Pigmets- Carotenoid Pigmets-Carotenoid pigments have color range from yellow to red. Mixture of acetone and hexane in the 1:3 ratio is used for the extraction of carotenoid pigments. The acetone layer on the extracted carotenoid pigments is removed with water. To remove the hexane residue, make treatment of hexane residue with activated MgO2 diatomaceous earth column. In this way, remaining of hexane and acetone can also be removed. Annatto Natural Pigments Annatto pigments are given 'annatto' name because these pigments are derived from Annato shrubs. These pigments have reddish-orange colorant. This colorant is derived from seeds of Achiote trees. The concentration of annatto pigments in the annatto shrubs, vary from place to place.
Uses of Annatto Pigments
When the foodstuffs require hues of yellow to orange, annatto based pigments are used. The main food items in which annatto dyes are used are: in making cheese (around 50%), for fish processing (around 20%), confectionery (around 10%), diary products except cheese (around 20%) Limitations of Natural Pigments *.Natural pigments are produced by traditional methods.
*.These pigments have lower intensity in comparison to Synthetic pigments.
*.Application with few mordants like alumina and iron, has adverse effects on the environment.
*.The liquid waste of natural pigments contains heavy metals which is much more than the desired limit.
*.These pigments are not efficient for coloring of the synthetic clothes.
*.To obtain same depth level like synthetic pigments, natural pigments require a large quantities of raw materials.
*.To ensure adequate wash and light fastness, these pigments require application with different metallic mordants. Kinds of Natural Pigments Apart from the above mentioned natural pigment, there are some more types of natural pigments present:
* Betalain Pigments *
Betalains are the another type of color pigments which are also derived from plants. These pigments are present in two forms. The first is b-cyanin having purple-red color and in the high concentration. The second is b-xanthine which is yellow in color and in low concentration. These pigments can easily be extracted from plant tissues with water as these pigments are highly soluble in water. The extracted water is then mixed smoothly with ethyl alcohol in 1:1 ratio. The use of ethanol in the mixture is to reduce the enzymatic action, otherwise the pigments will be degraded.
* Plant pigment like chlorophyll *
Acetone is required for the extraction of plant pigments. Calcium carbonate must be present there for stimulating the extraction process. Any other mild alkali can also be used for the extraction of plant pigments. The alkali is used during the extraction process due to neutralizing the acid which liberates from the plant tissues. This neutralization prevents the formation of pheophytins during the extraction process, unless the the pheophytins may block the extraction process. Following diagram is the pigment structure of anthocyanidin pigments (flower pigments)
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