1. DESIZING PROCESS COMPLETION TEST (TEGEWA)
Before yarn is woven into fabric, the warped yarns are coated with sizing chemicals such as starch, binder and softener to impart strength required for weaving on looms. Sizing is essential for weaving but is an obstacle for dyeing and printing. Therefore desizing is done in which ‘size’ (mainly starch) is removed from fabric for good dyeing, printing and finishing.
TEGEWA test is performed after this process to check the removal of starch. Bad quality starch/filler used in sizing recipes to increase fabric GSM creates problems for removal and should be avoided.
Method
• Dissolve 10 gm of Potassium Iodide (KI) in 100 ml of water
• Dissolve 10 gm of Potassium Iodide (KI) in 100 ml of water
• Dissolve 10 gm of Potassium Iodide (KI) in 100 ml of water
Application: Put the fabric sample in the Iodine solution for 1 min and immediately compare the results with violet scale.
Observations:
• < 5: incomplete starch removal
• 5-7: satisfactory desizing
• 7-8: good desizing
• 8-9: complete starch removal
OUR RECOMMANDATIONS FOR BETTER PRINT /DYE RESULTS- TEGAWA RATING: 7 to 9
2. SCOURING PROCESS COMPLETION TEST (ABSORBENCY)
Scouring is a chemical washing process carried out on cotton fabric to remove natural wax and non-fibrous impurities and any added soil or dirt from the fibres.
It is a micro cleaning process where softeners, oils, wax, gums and dirt which are commonly found in cotton and rayon fibres are removed to produce a hydrophilic (absorbent) fabric which provides a better adhesion for dyes. There are two methods for checking fabric absorbency:
A. DROP TEST
This method is designed to measure the water absorbency of fabric by measuring the time it takes a drop of water placed on the fabric surface to be completely absorbed by the fabric.
Sample is placed over the top of the beaker so that the centre is unsupported. A measured drop of water is placed on the fabric from 1 cm off the surface, time is recorded until the water drop gets absorbed completely.
B. WICKING TEST
This test method measures the distance water will wick up an edge of the fabric. The rate of liquid travels along and through a vertical fabric specimen is visually observed, timed and recorded at specified intervals.
The sample taken is of 2.5 cm wide & 17 cm long. The sample is submerged by 1 cm in Di-ionized colored water. A measurement of how far the water has moved along the edge of the fabric vertically is measured in every 1, 5, 10 and 30 min intervals.
3. BLEACHING PROCESS COMPLETION TEST (WHITENESS INDEX)
Bleaching is a process which improves fabric whiteness by removing natural coloration and remaining trace impurities from the fabric.
Whiteness index is the measure which correlates the visual ratings of whiteness for certain white and near white surfaces.
After completion of bleaching process which removes natural colouring matter from the fabric one must have to measure the whiteness index of the fabric to check th e effectiveness of the bleaching process.
Most commonly used method for computing whiteness index is CIE Whiteness Index method.
OUR RECOMMANDATIONS OF WHITENESS INDEX FOR BETTER RESULTS:
• PRINTING : 70 + WHITENESS INDEX
• DYEING : 50 + WHITENESS INDEX
