Textile printing is the most versatile and common method used for decoration of any textile fabric. It may be regarded as a specialised technique of dyeing. The main idea of printing is the deliberate and controlled application of dye to an exactly defined location on the fabric, leaving the rest of the fabric essentially unaffected.
Printing is an applied art. It existed before weaving or embroidery and its development still continues. Besides dye, thickener also plays an integral part of printing, without which printing cannot be done. Thickeners are generally higher-molecular-weight compounds giving viscous paste in water. The viscosity of the printing paste is very important, as it influences the clarity and appearance of the printed pattern.
The main function of thickener in printing is to act as a vehicle for carrying the dye on to the cloth and thus preventing capillary action from causing the dye to spread beyond the limits of the defined portion in the pattern, through its viscosity and adhesive nature. During steaming, the adhesive nature of the thickener holds the dye particles while the fabric becomes saturated with steam and the chemical reactions take place, giving the dye good fastness properties.
Natural thickeners widely distributed throughout the plant kingdom; they are easily available and present in abundance. Since these are renewable resources, therefore they can be sustainable raw materials for the textile industry. As the ingredients of natural thickeners are purely natural, they are non-allergic and non-toxic to our body and cause no health hazard. Hence, the present study was undertaken to print cotton fabric using tapioca as a thickener, to standardise printing recipes and to develop various articles using standardised recipes.
Methodology 
Raw Materials
Tapioca was used as a natural thickener for printing of cotton fabric. Two synthetic dyes, namely direct and reactive dye, were used for the study as these dyes are more suitable on cellulosic fabrics.
Scouring of Cotton
Before printing, the entire length of cotton fabric was scoured to remove the natural and added impurities which can hinder the process. The entire length of fabric was soaked overnight in water. The fabric was then boiled in a solution containing 2g soap and 1g of NaOH per litre of water for 45 minutes. It was kneaded, squeezed in the soap solution. After that, fabric was partially dried in shade and ironed when half-wet (Singh and Gahlot, 2005).
Preparation of Screens
Screens were prepared by stretching nylon mesh tightly over a wooden frame. The design was drawn and painted with enamel paint to block out those portions which were not required to be printed.
Preparation of Thickener Paste
Firstly, tapioca roots were peeled, washed properly and sliced so that they could be dried easily in the sun. After drying the root was ground to a powdery form and sieved to remove any lumps or unwanted substances. The refined flour was mixed with water to form a paste and then heated until a thick paste with grey transparency was acquired. The paste was then ready for use.
Optimisation of Thickener Concentration 
The concentration of thickener was optimised. The printing pastes (for each dye) were prepared separately by taking 50, 60, 70, 80, 90, 100g thickener concentrations, keeping the other ingredients the same as taken earlier (recipe given by Shenai 1976). Samples were printed with these pastes using a screen and each sample was subjected to physical testing and also evaluated visually to select the best thickener concentration for each dye (direct and reactive dye).
Optimisation of Dye Concentration
The concentration of each dye was also optimised. Selected thickener concentrations were taken separately with different dye concentrations, ie. 1, 2, 3, 4, 5, 6g (both direct and reactive dye) for preparation of printing paste, keeping the other ingredients the same as taken earlier, and cotton samples were printed with these pastes. The samples were tested for colourfastness to such as light, washing, perspiration and crocking, and given a visual evaluation, to select the best dye concentration (both direct and reactive dye).
Results and Discussion
Cotton fabric was printed with direct and reactive dye using tapioca thickener in different concentrations and the printed samples were subjected to physical testing, for selection of best thickener concentration. Optimisation of dye concentration was done through colourfastness and visual evaluation. A total 12 samples were tested for physical properties (thickness, bending length, crease recovery, drape, tensile strength and pilling test) and colourfastness, together with visual evaluation. The results are discussed one by one.
Optimisation of Thickener Concentration
Thickness
It is evident from the Table 1 that the thickness of cotton-printed samples using tapioca thickener ranges from 0.23mm to 0.26mm (both direct and reactive dye), with an average of 0.24mm.
The thickness of printed samples with 50 and 60g thickener concentration showed the same value of 0.23mm for both direct and reactive dye. The other printed samples showed increased thickness with an increasing amount of thickener in both the dyes. This means that 50 and 60g showed the lowest value and 100g showed the highest value in both the dyes. It was also found that the thickness of the control sample of cotton fabric is 0.20mm and thickener applied through printing paste further increased the thickness of the fabric.
Stiffness
According to Angappan (2002), the lower values of bending length of sample shows less stiffness, which is a desirable property for apparel.
Thickener concentrations of 50g and 60g showed nearly the same results with the least value of all and 100g showed the highest value in both the dyes. All the printed samples showed increase in bending length with increasing thickener concentrations. Therefore the higher the thickener concentration, the higher will be the bending length and the greater will be the stiffness of the fabric, which is undesirable for apparel.
Crease recovery
According to Angappan (2002), crease-recovery angle is the measure of wrinkle recovery or crease resistance of fabric, which enables a fabric to resist wrinkling. The more the angle, the lesser will be the fabric stiffness and thereby good crease recovery will be exhibited.
It is evident from the table that all the samples printed with different thickener concentration showed a high crease-recovery angle in the weft direction for both direct and reactive dye.
The results of crease recovery showed that among the different thickener concentrations, 50 and 60g showed nearly same value in each dye. Other concentrations showed decreasing value with increasing thickener concentration, having 100g as the lowest value for both the dyes.
Drape
Drape is defined as ‘the extent to which a fabric will deform when it is allowed to hang under in its own weight’; Kankare and Plumlee (2005).
Table 2 shows that all the printed samples showed almost similar drape percentage, and the values increased with increasing thickener concentration.
Tensile strength
The results from Table 2 show that the printed samples in the warp direction had a higher value than the weft direction, which means that the warp is stronger than the weft and the value ranges from 34.31kgf to 35.88kgf for the warp and 31.02kgf to 33.13kgf for the weft.
The table also revealed that the value decreases with increasing thickener concentrations (except 60g), which means that the printed samples become weak with more thickener. This may be due to the accumulation of thickener in the fibre making it brittle, which in turn decreases the fibre strength...
The elongation percentage ranges from 10.11% to 10.79% in the warp direction and 12.03% to 12.68% in the weft direction, which increased with increasing thickener concentrations.
Optimisation of Dye Concentration
Colourfastness
The colourfastness of all the printed samples against light, washing, perspiration and crocking was found to be good. The results showed better colourfastness for acidic perspiration solution than alkaline perspiration. Similarly, the results for dry crocking fastness were better than for wet crocking fastness with regards to change in colour and staining on adjacent cotton, for all the printed samples.
Out of the various concentrations (1g, 2g, 3g, 4g, 5g and 6g) of direct dye and reactive dye, the results obtained through colourfastness and visual evaluation showed that 2g of direct dye and 3g of reactive dye gave best results. Hence 2g of direct dye and 3g of reactive dye was selected as optimum for printing of cotton fabric.
Conclusion
Tapioca was found to be a good source of natural thickener for printing of cotton fabric, and from the various results of physical testing, it was found out that 50 and 60g thickener concentration showed nearly similar values. But, when visually evaluated, the best result was obtained by 60g concentration for both the dyes. Therefore 60g concentration was selected as optimum (both direct and reactive dye) for printing of cotton fabric with standardised dye concentration of 2g direct dye and 3g reactive dye.
Nowadays, with increasing global pollution and the concern of maintaining healthy environment, natural products are preferably acceptable and, since tapioca is a renewable resource, therefore it can be a sustainable raw material for the textile industry.
References
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