Tuesday, December 29, 2009

Dyeing with Direct dyes

Dyeing Method With Direct Dyes
 Direct Dyes
Direct Dyes are used in wide range of dyeing applications such as on Cotton, Silk and Viscose Fabrics. Direct dyes are Famous for their easy application, leveling property, good brightness and fastness. These dyes can be safely applied on Textiles and Leather.
Good pre-treatment is essential if satisfactory dyeing is to be obtained. To get better depth and fair brightness, Grey Fabrics must be free from impurities like sizing materials and spinning oil by boiling the Grey with alkline or some times bleaching also carried out in case of pale shades.
The dyestuff is pasted with cold water and dissolved by pouring 50 to 100 times its weight of Boiling water while stirring. The solution may be boiled to ensure complete dissolution. For Certain dyes, which are dyes from and alkline dye bath, it is preferable to add half its weight of soda ash while pasting with water.
Set the Dye Bath at 50°-60° C temperature with dyes solution, salt and soda ash. Run for 15 Minutes. Gradually raise Temperature to 90°-95° C. Run for 30 to 45 minutes. In order to Overcome un level dyeing salt may be added in installments after about 15 minutes of initial dyeing prior to raising the dye bath temperature.
In the case of dyestuff which possess maximum affinity at temperature below boil, it is preferable to start dyeing at boil, dye for 15 to 20 minutes and then add salt in two installments to exhaust the bath and continue dyeing in a cooling bath (60° c) for 15 to 20 minutes.
The dyeing on the Jigger is carried out as follows:-
First End : 1/2 quantity of Dyes solution, soda ash and 1/4 quantity of Salt at room Temperature. Second End : 1/2 quantity of Dyes solution, 1/4 quantity of Salt at 60°)c, raised to 80°c.Third End : 1/4 quantity of Salt.
Fourth End : 1/4 quantity of Salt.
The temperature is raised to raised to boil and four ends are given at boil. Finally the dye-liquor is Drained and further two ends are given in cold water.
Fastness to wet treatments can be improved by after treatment with 1-2% Cationic Dye Fixing Agents at 40-50° c for minutes.
In case of some selected dyes, light fastness can be improved by after treatment with:-1-2% Copper Sulphate1-2% Actic (30%) at 80° c Temperature.


  1. Is it necessary to use soda ash in this case of dyeing? Addition of common salt/gluber salt as leveling agent could serve the purpose.

  2. Soda ash is needed to help solubilize the dyes (especially when a lot of color) and to slow the rate of adsorption. Salt is used for the purposes of exhaustion. Very important is the use of suitable leveling nonionic / weakly ionic.


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