Sunday, 12 July 2009
The Rapid dyes are stabilized dyestuffs specially prepared for printing.
They are applied to the fibers in one operation.
Bright full colors are obtained with very good fastness properties.
These are used for printing backgrounds so that the foreground becomes prominent. Hence these are suitable where large areas of ground need to be colored.
Rapid dyes are mixed with water and boiled with caustic soda and a gum paste. A receipe for rapid dyes is given here.
The shades in rapid dyes are unpredictable since the color that is mixed is different from the final color.
True colors emerge only after the fabric has been printed and washed in a mild sulphuric acid solution.
Also these dyes should be used on the same day.
Some colors such as pure blacks are extremely sensitive to weather. Similarly red colors in rapid is vibrant in summers and mediocre in winter