In recent years the usage of natural dyes and colors for fabric dyeing has witnessed its revival due to hazardous experience due to effects of synthetic dyes and chemicals. The natural dyes are eco-friendly, harmless and non-toxic in nature. Also, the usage of renewable sources of energy in textile and apparel industry has been increased due to many advantages associated with it. Solar energy usage for dyeing purpose is a cost effective method. In hot countries like India, the sun shines bright for 60% of the day, using solar energy to dye silk fabric with turmeric dye is cheap and environment friendly method.
There are certain things required in order to dye the silk with turmeric dye which are listed as follows- turmeric plant stems, raw silk fabric yarn, diluted nitric & acetic acid and mordants like alum & stannous chloride.
Before applying the dye to the fabric the process of removing sericin from silk is done. Here the silk fabric is first treated with ezee kept in it for approximately one hour then washed and dried. This whole process is known as degumming.
Enhancing of Dyeing Parameters
To dye the silk fabric with turmeric dyes certain procedures are to be followed. The dye dilution, the time taken for its extraction, time for dyeing, amount of mordant used and mordant process are to be taken care of to result into turmeric dyed silk fabrics which is evenly dyed with no color patches or differences in shade.
Not only yellow color is produced through dyeing with turmeric dyeing but also many other colors are produced when turmeric dye is mixed with other colors, like – orange, green, blue color with addition of indigo and red color with addition of safflowers and mango rind.
You might think how both red and yellow colors are produced through turmeric dye in its original form, the answer lies in the type of liquid used for concentration. When the solution is prepared in acidic liquid it would produce yellow dye and when alkali liquid is used it would produce red dye.
Time for Dye Extraction:
In order to extract the dye, aqueous mode is utilized. The dye is examined for its evenness and color shade by quality control supervisors before applying to the fabric. The turmeric powder is which is one gram is diluted with 100 ml of water. Four such solutions are prepared. Each one is boiled for four different time period i.e. 20, 40, 60 and 80 minutes in a solar cooker.
Time Taken for Dyeing:
The optimum dye solution is utilized to standardize the dye concentration. The dyes undergo the procedure of absorption in the solar cooker time ranging from 30-180 minutes. The absorption power of the silk fabric determines the dyeing time
Concentration of Acid:
The two acids used for dilution are acetic and nitric acid. From each of diluted acid, 20 ml is mixed into the dye bath. The dyes are examined for their absorption power. This examination is done visually.
The mordants discussed earlier Alum and Stannous chloride are used here. The process of dyeing and mordanting are done together. Both these mordants are mixed with water which results into optimized mordants.
Procedure for Mordanting:
There are two methods in mordanting premordanting and postmordanting. The prerequisite of this process is to keep other things like dyeing time, acid concentration, etc. steady. By looking at the dyes the method of mordanting i.e. pre or postmordanting to be used is decided.
They are also categorized by the generations as they were produced in the different years and known as first generation, second generation, third generation or fourth generation fibres. This is given in the below chart:
Appropriate Dyeing Conditions:
1. The right level of dye concentration is 3g per 100ml of water used for 1 gram for silk fabric as it was observed that the percentage of absorption of dye by silk fabric is best if done in this measurement.
2. As stated earlier four different dye extraction time was used- 20, 40, 60 and 80 minutes, however it was found that 60mins/1hour time duration produced turmeric dye with maximum absorbency.
3. The right level of acid concentration in dye bath is, for acetic acid is 2% and 3% for nitric acid. After this concentration the dye absorbency decreases.
4. The best concentration for mordants was 0.4g for stannous chloride and 5g for Alum. Use of appropriate mordent concentration helps in better absorption of turmeric dye on silk fabric.
5. It was found that the turmeric dyes absorbency was better with stannous chloride and postmordanting method was better than premordanting method.
The silk fabric dyed with turmeric dye using solar energy gives better results. Color evenness and better dye absorbency is experienced when dyeing the silk fabric by turmeric dyes. The existing silk dyeing units are being encouraged to use turmeric dyeing method. It does not pose any chemical harm on part of the dyer as well as the wearer. Also the added benefit is that the government also supports such environment friendly processes.
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