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Efficiency of Desizing:
Desizing efficiency is found in two ways conventional and TEGEWA method.
Conventional Method:
In this method we first take the weight of the sized fabric, let it be W1. Then desize the fabric, dry & take the weight, let it be W2. After that the fabric is treated with 3gpl (35%) HCl at 700 C for 30 min. dry & take the weight of the fabric. Let it be W3.
Total size = W1-W3.
Residual size = W2-W3.
Desizing Efficiency = (Total size – Residual size)/Total size X 100.
TEGEWA RATING:
Reagent: potassium iodide (10 gm. Of KI (100%) in 100 ml water, add 0.6358 gm of iodine (100%) stir and shake; iodine is completely dissolved. Fill up to 800 ml with water then complete to 1000 ml with ethanol. (Shelf life approx 6 months only).
Method:
1. Spot drop wise solution onto fabric.
2. Rub in gently.
3. Assess change of colour.
Note: the test must be carried on fabric cooled down to room temperature; residual alkalinity has to be neutralities prior to the test.
Assessment:
Grey fabric:
No change of colour = no starch size present.
Pale blue to bluish = presence of starch size or blend
Violet =of starch size with synthetic size
Desized fabric:
Pale blue to bluish violet = refer to violet scale TEGEWA This indicates residual Starch content.
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