How to test scoured cotton material:

As we understand cotton is scoured using alkali at boiling temperature. During or after scouring, it is must to know whether the material scoured properly or not. To ascetain that a simple drop test can be performed. In such type of test, if the material is under scouring process, a small piece of fabric is cut from the lot of fabric which is running in the machine say jigger (after stoping it). The piece is washed properly under tap water (Soft water) and dried using iron or placing the fabric piece on hot steam pipe line. After cooling the fabric, a drop of water is allowed to fall on this piece of fabric. If the drop is absorb whithin few seconds say 3 seconds, one can be assured that scouring is perfectly done. However, if the drop is taking much time to absorb, there is a need to continue the scouring process untill the fabric acquire optimum absorbency. If the fabric is being scoured for printing process, it is required that the water drop should be absorbed within 1 second. There are standard tests are also availabe for testing absorbency of fabric in the laboratory e.g IS 2349 and AATCC 79.

How to test desized material (Starch based size):

To test the presense of sizing material i.e starch based sizing material in the fabric iodine test is conducted. In which the fabric is spotted or treated with  Iodine solution —Iodine dissolved in an aqueous solution of potassium iodide, which reacts with the starch and produce a bluish-purple-black colour. If there is no starch the colour may be brownish-yellowish.  In the below figure, it is explained that if the iodine solution is added in the solution ( which you want to know whether there is a starch or not) if there is a starch then you may get purple/bluish colur solution. If there is no starch the colour remain same. 

TEGEWA solution is also used for the identification of starch.  For making this solution potassium iodide 10 g of KI (100%) in 100 ml of water is added with 0.6358 g of iodine (100%) and shake this well to disslove iodine crystals. Then make it up to 800 ml using distilled water and finally make it up to 1000 ml with ethanol.

High Pressure Kier with multitubular heater:

The modern high pressure kier with multitubular heater is also known as  Walsh's kier and one of the best kier. The 2 ton capacity kier is most common which is about 9 ft high and 6.5 ft in diameter and mounted on R.C.C Coloumn. The kier works at working pressure 40 lb/sq inch at 141 degree C and is composed of mild steel plates. The kier is provided with pressure gauge, safety valve, blow off valve for air, steam trap, liquor level indicator, drain cock etc.

The goods in rope form are plaited either manually or mechanically plaiting on the perforated false bottom. The cloth can be saturated with alkaline solution containing the recipe as given above with figure.

During piling sufficient scouring liquor is   added to the kier from the below to remove entrapped air from the goods to avoid the formation of oxycellulose. The lid is then closed but air valve is kept open. Steam is turned on and the liquor is circulated by centrifugal pump coupled to an electric motor. High pressure kier operate at about 8 to 10 hours with liquor ratio 1:3 to 1:5 (MLR). After scouring the drain cock is opened at reduced pressure (5 to 6 lb/sq meter) and equivalent amount of hot water is added from the top. After circulating cold water the goods are removed and washed in a rope washing machine. The liquor is withdrawn from the bottom of the kier and forced through the heater and spread over top of the load by distributor. Fabric which are to be sold in white state are given two boils and the fabric intended for printing single boil is sufficient.

 Precaution:

 Following precaution should be taken while using kier:

• Kier should be clean
• Material should be packed evenly.
• No air packed should be formed
• The fabric should be in liquor completely.

Souring:

The fabric after bleaching contains metallic salts such as calcium carbonate, magnesium carbonate etc., and other mineral matter. These salts, if left on the fabric, will not only give a harsh feel but also affect the uniformity of the shade during dyeing. In order to make these salts soluble in water, the fabric is treated with either dilute hydrochloric acid or sulphuric acid, the former is used for fabrics meant for dyeing whereas latter, being cheap, is used for fabrics meant for white finish. Hydrochloric acid which forms soluble calcium salts is better then sulphuric acid. The concentration used is about 0.5 to 1.0% on the weight of fabric.