What is Size?

Size or sizing is defined as the composition of matter applied to warp yarns, before weaving, for the sake of their protection against abrasive stresses during weaving. These abrasive stresses are caused by movement of the warp yarns through the heddles on the loom and mechanical actions during insertion of filling. Unprotected warp yarns will break during weaving, causing frequent machine stoppages and loss of productivity. The application of size greatly improves the weaving efficiencies. The size also glues down loose fibers and lets the yarn slide more easily during weaving.

Why identification of type of size (on the fabric) is important?

Sizing is called "devil's invention" by the textile dyer, since he must remove it in order to have a defect-free, uniform, well penetrated dyeing. In order to assure the best removal of sizing, the identification of type of size is important, as different type of sizes need different removal strategies or different optimum desizing recipes.

Scheme 1 for identification of type of size

Preparation of Test Solutions:

Solution 1: 2.4 g of potassium iodide and 1.3 g of iodine dissolved in water and diluted to one litre.

Solution 2: 0.13 g of iodine, 2.6 g of potassium iodide and 4.0 g of boric acid added in that order and diluted to 100 ml.

Solution 3: 11.88 g of potassium dichromate and 25 ml of concentrated sulphuric acid diluted to 50 ml with water.

Solution 4: 30 g of sodium hydroxide in 70 ml of water.

Solution 5: 0.012 M ferric chloride.

Solution 6: 0.06 M potassium thiocyanate.

Solution 7: 0.005 M potassium ferrocyanide.

Solution 8: Iodine and boric acid

Solution 9: Chromic acid.

Solution 10: Sodium hydroxide

Procedure for Identification of Starch, PVA and CMC (Fig. 1)

Step 1: Spot fabric with one or two drops of solution 1. Formation of a deep blue colour indicates the presence of starch or PVA.

Step 2: (Only if you know that starch is not present) Spot fabric with one or two drops of solution 2. A purple colour indicates the presence of PVA.

Step 3: Apply on fabric one drop of solution 3 and immediately neutralise with 3-4 drops of solution 4. Wait for 5 seconds, and then rub mixture with a glass rod. Formation of a brown spot indicates presence of PVA.

Step 4: Mix thoroughly 5 drops each of solution 5 and 6. Spot the fabric with one drop of this mixture and let stand approximately 3 minutes. Rinse in running water for 10 seconds and blot dry. Add one drop of solution 7 and let stand 1 minute. Rinse in running water 5 seconds and blot dry. A blue or blue-green spot indicates CMC.