Simple aqueous methods
This is the one of the simplest and oldest method employed for the extraction natural colouring components
globally. Here in this technique, the raw materials are first dried, and finely cut, most of the times grinded in the
powder form and then the colouring components were extracted in water at boil. After the boiling for specific time,
the content is cooled to room temperature and filtered. The filtrate is used as a dye for dyeing. The aqueous
extraction of colorants liquid are carried out under various conditions such as temperature, time of extraction, pH,
raw material concentration and Material to Liquor ration (MLR). Thus, the optimum extraction condition is
determined for a particular dye by studying the maximum absorbance or optical density value at a particular
(maximum) absorbance wavelength for the aqueous extracted solution using UV-Visible absorbance spectrophotometer.
There are different researchers who have explored the extraction by aqueous method and optimized the process.
Khan et.al (2006) [77] have explored the extraction of biomass products namely cutch, ratanjot, madder. Maulik and
Pradhan (2005) [78] studied hinjal, jujube bark in aqueous medium. Natural colour extraction process has also been optimized in aqueous media for various source natural dye materials [79] are carried out and given in Table 3.