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10.1 Desizing
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Assessment of desizing efficiency
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The weight loss can be used as criteria for assessment of desizing efficiency |
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The weight loss is of the order of 7-10% |
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The more scientific method, which is used industrially also, is TEGEWA rating test |
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(Applicable for starch based sizes only)
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It is a scale, which consists of colours ranging from violet to white as given below. |
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TEGEWA SCALE |
The TEGEWA Association comprises of manufacturers of the following: Textile, paper, leather and fur auxiliaries and colourants, surfactants, complexing agents, antimicrobial agents, polymeric flocculants, cosmetic raw materials, pharmaceutical excipients and allied products. |
TEGEWA was established in 1951 in Wiesbaden as an association of the manufacturers of chemicals, the name being an amalgam of these key activities: TExtilhilfsmittel” (textile auxiliaries), “GErbstoffe” (tanning agents) and “WAschrohstoffe” (detergent raw materials). |
Reagent preparation |
- Ten gram (10 g) potassium iodide (KI,100%) is dissolved in 100 ml of water
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- To the solution, 0.6358 g of iodine (100%) is added
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- The mixture is stirred well until iodine is completely dissolved in the KI solution.
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- To the solution, 800 ml of ethanol is added
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- The volume is to 1000 ml by adding water
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Method of testing |
One or two drops of the above solution are put on the desized fabric and rubbed gently. The fabric should be cold and free from any residual alkalinity. In a short time the color of the spotted area changes. The change in color is assessed with TEGEWA scale visually. |
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Assessment |
No Colour Change = No starch is present |
Pale blue to bluish violet = Presence of starch size or a blend of starch + synthetic size |
Brown = Presence of modified starch or a blend of starch/PVA size |
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