Printing Methods; Methods of textile printing

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Methods of Printing 

There are three basic approaches to printing a color on a fabric. Direct, Discharge and Resist. Transfer Printing is comparatively a new method which is also gaining popularity Direct Printing. The most common approach for applying a color pattern is direct printing. It may be done on a white fabric or over a previously dyed fabric, in which case it is called overprinting. The dye is imprinted on the fabric in paste form, and any desired pattern may be produced. The dyes are usually dissolved in a limited amount of water to which a thickening agent has been added to give the necessary viscosity to the print paste. 

Direct Printing Method

The principle of direct printing is creation of a colored design by applying a dye or pigment directly onto a textile substrate (yarn or fabric). Discharge Printing. Another approach for applying a color pattern is discharge printing. The fabric is dyed in the piece and then printed with a chemical that will destroy the color in designed areas. Sometimes the base color is removed and another color printed in its place, but usually a white area is desirable to brighten the overall design. When properly done, discharge printing gives very good results; however, the discharged areas may literally fall out of the fabric if the goods are not thoroughly washed after printing (a rare situation today). The usual method of producing discharge prints is to print the design, such as polka dots, with a paste containing a reducing agent. A steaming follows and then there is a good washing to remove the by-products of the reaction. Resist Printing A third approach to obtaining a color pattern is resist printing. Bleached goods are printed with a resist paste––a resinous substance that cannot be penetrated when the fabric is subsequently immersed in a dye. The dye will affect only the parts that are not covered by the resist paste. After the fabric has passed through a subsequent dyeing process, the resist paste is removed, leaving a pattern on a dark ground. Their are several other methods also for printing textiles. Two are of significant commercial importance: the screen print method and the roller print method. A third method, heattransfer printing is a comparatively new concept & less significant. Other printing methods rarely used in commercial production of textiles are block, batik, ikat, and resist printing. Many textile printers print fabrics in both screen and roller methods. Most heat-transfer printing is done by printers that specialize in this method. 

Batik 

Batik cloth is made by a wax-resist process. The name batik originates in the Indonesian Archipelago, where resist printing has become an important art form. Wax is applied to the areas that the printer does not want to dye. In Indonesia a small, spouted cup with a handle called a tjanting is used to apply the wax. Melted wax is poured from the tjanting onto the cloth. When it hardens, the wax coats the fabric so that the dye cannot reach the fibers. 

If several colors are to be used, the process becomes somewhat more complex. For example, if a fabric is to be colored white, red, and blue, the artisan begins with a creamywhite cotton cloth. Those areas that are to remain white and those that are to be red are coated with wax. The fabric is now subjected to a blue dyebath, and the exposed areas take on the blue tint. The wax is boiled off and reapplied to cover the blue and white areas. When the fabric is placed in the red dyebath, the color penetrates only the uncovered areas of the design. After dyeing is complete, the fabric is treated with a fixative (a mordant) to make the colors fast, and a final rinse in hot water removes all traces of wax. For faster production a technique was devised whereby the wax could be printed onto the surface of the fabric with a device called a tjap. The design is carved on a tjap block, the block is 

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PRINTING

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Textile Printing

Printing has often been described as dyeing in a localized area to create patterned design. Creating design interest in fabrics can be accomplished in several ways, including yarn variation (novelty yarns). Weave variation (dobby and jacquard), and color effects in weaving. An additional color design can be created through the process of printing design shapes onto previously woven, knitted, or non-woven fabrics. 

Textile printing uses the same dyes or pigments applied to produce dyed fabric. The same principles of specific dye classes having select fiber affinities and the general fastness characteristics apply equally to printing and dyeing. 

The designs for printed fabrics are an important element of the printed fabrics industry. A continuous supply of new designs are required for this highly fashion oriented segment of the textile industry. 

Dyes or pigments used in dyeing are usually in a water bath solution. When the same dyes or pigments are used for printing, they must be thickened with gums or starches to prevent the wicking or flowing of the print design. The thickened solution, about the consistency of heavy buttermilk, is called the print paste. Some dyes cannot be used in printing pastes for reasons such as insufficient solubility and low color yield. 

The application of a pattern to fabric by the use of dyes, pigments, or other colored substances may be effected by a variety of hand or machine processes. Freehand painting of designs on fabrics is probably the oldest technique for applying ornament, but hand painting is a time-consuming procedure. Furthermore, it does not always result in a uniform repeat of a motif that is to be used more than once. If a design is transferred to a Bat surface that can be coated with a dye and then stamped onto the fabric, the same design can be repeated many times over simply by pressing the decorated surface against the fabric. This process is known as printing. Over many centuries a variety of techniques for printing designs have evolved. Printing can be applied to warp yarns, to fabrics, or to apparel pieces-for example, slogans or pictures on T-shirts. 

In general, printing is a cheaper way of creating designs on fabric than weaving or knitting with different colored yarns. Printing can be done with dyes or pigments. For pigments it is necessary to use an adhesive to bind the colored substance to the fabric. Different methods for applying designs can be combined with a number of printing tools or machines to provide the printer with a variety of processes. 

Methods of Printing 

There are three basic approaches to printing a color on a fabric. Direct, Discharge and Resist. 

Direct Printing 

The principle of direct printing is creation of a colored design by applying a dye or pigment directly onto a textile substrate (yarn or fabric). Discharge Printing. Another approach for applying a color pattern is discharge printing. The fabric is dyed in the piece and then printed with a chemical that will destroy the color in designed areas. 

Batik 

Batik cloth is made by a wax-resist process. The name batik originates in the Indonesian Archipelago, where resist printing has become an important art form. Wax is applied to the areas that the printer does not want to dye. 

Methods Of Direct Printing 

Block Printing

The oldest method of printing designs on fabric is block printing by hand. It is not commercially important today because it is too slow 

Roller Printing 

Roller printing is the machine method of printing designs on cloth by engraved rollers. It turns out color-designed fabrics in vast quantities at the rate of 1000 to 4000 yards (914-3658 m) an hour. This method of producing attractive designs is relatively inexpensive when compared with any hand method. 

Rotary Printing 

A printing machine that utilizes seamless cylindrical screens made of metal foil was originally developed in Holland. This process is called rotary screen-printing. 

Screen Printing

Originally, this technique was referred to as silk-screen printing because the screens were made of fine, strong silk threads. Today, they are also made of nylon, polyester and metal. Screen printing is done with the use of either flat or cylindrical screens. 

Heat Transfer Roller Printing 

Like traditional roller printing, heat transfer printing is done by passing the fabric around a central drum or cylinder where it contacts a roller for transferring the design. The roller is followed by a heating zone to effect the sublimation of the dye. Since all colors are applied to the fabric at the same time, 

Other Printing Techniques 

Photographic Printing 

Photographic printing is done in a manner similar to the photochemical preparation of screens for screen printing. A photosensitive dye is coated on the fabric, a negative is placed over the fabric, light is applied, and a photographic type of printing takes place. 

Electrostatic Printing 

Electrostatic printing is an experimental process in which a plate with an electrostatic charge is placed behind the fabric. A stencil in the form of the pattern is placed over the fabric. Special powdered inks that can be attracted by the electrostatic charge are passed over the surface fabric, and the inks are attracted into and color the fabric in the open areas of the stencil. 

Flock Printing 

By imprinting an adhesive material on the surface of a fabric in the desired pattern, and then sprinkling short fibers over the hesive, a flocked print may be created.

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TEXTILE ECONOMICS; Product Costing Methods, Job Order Costing System and Process Costing

Product Costing Methods 

The Basic methods of product costing are: 

Job Costing: allocates costs to products that are readily identified by individual units or batches, each of which is independently identifiable. When using the job cost system, costs are accumulated for each individual unit produced, or each separate order of products. This method is especially useful when producing something that is unique or custom-made. Job order costing would be used bya caterer, a garage, a helicopter manufacturer, a construction company and a textbook publisher, 

Contract Costing: a subset of job costing which is applied to relatively large cost units which take a long time to complete, typically over a year (e.g. civil engineering projects, ship building, building and construction etc). A separate account is maintained for each contract. Contract accounts involve: 

• determination of cost of sales 

• annual comparison of value of work certified as a proportion of the contract value and the costs to date as a proportion of total costs as a means of assessing the profit that should be recognised 

• record of payments received on account 

• records future expenses and accrued expenses 

Guidelines for Determining Profit to Date on Contracts No Profit is taken if contract is at an early stage. Reliability (prudence) concept is applied and losses are recorded as incurred or anticipatedIf the contract is near completion a proportion of the profit should be recognised having regard to work certified and costs to date 

Process costing: is applied when goods or services are produced from a series of repetitive or continuous processes or operations and the costs of processing are charged to the process as a whole before being averaged out over the units produced during the period. Process costing is used in a variety of businesses including distilling, water distribution, textiles, paint mixing and glass manufacture. 

Job Order Costing System 

The basic records maintained in a job-costing system include: Job-cost sheet (also called job-cost record or simply job order): records all costs for a particular product, service or batch of products are recorded on the job-cost sheet from: 

Materials requisitions: detail materials and components drawn from stores for particular jobs are priced and summarised, and entered as direct material costs on the job-cost record. Labour time records: show the time a particular direct worker spends on each job and are summarised to give direct labour cost on ‘the job-cost sheet. The manufacturing overhead will often be based on these labour hours or otherwise separately calculated and entered on the job cost sheet separately 

Actual rate vs. predetermined rate (normal) costing system 

Job-costing systems uses actual costs of direct labour and materials to determine the cost of individual jobs. However, a problem arrives with overhead costs, which are dependent on what is happening to the other jobs that are in process at the same time and can only be known after the event. Actual rate costing is a method of job costing that traces indirect costs to a cost object by using the actual indirectcost rate(s) times the actual unit of absorption base (direct labour, machine hours etc.), Predetermined rate (normal) costing systems use estimated amounts (at a normal level of activity) for the manufacturing overhead costs that are applied to each job and estimated amounts for the absorption base to calculate a predetermined overhead rate. This rate is based on the total estimated overhead costs for the period and the estimated usage of the absorption base (e.g. machine/labour hours). 

General Approach to Job Order Costing 

The following seven-steps approach is used to assign actual costs to individual jobs 

l Identify the chosen cost object(s) 

2.Identify the direct costs of the job 

3.Select the cost-absorption base(s} 

4.Identify the indirect costs associated with each cost-absorption base 

5.Compute the rate per unit of each cost absorption base to allocate indirect costs to jobs 6.Compute the indirect costs allocated to the job 

7.Compute the cost of the job by adding all direct costs assigned to it 

Process Costing 

Process costing (a.k.a. continuous operation costing) is a method that is applied when goods or services are produced from a series of repetitive or continuous processes or operations and the costs of processing are charged to the process as a whole before being averaged out over the units produced during the period. ‘A process costing system involves the costs of producing similar items being accumulated and allocated to the products by averaging costs over large number of nearly identical products. The average cost per unit is calculated by dividing the total production cost by the number of units produced. Process costing would be used by businesses such as food processors, household product manufacturers, chemical processors and oil refiners.. 

General approach to process costing 

I. collect cost data for the period on production cost report; 

2. prepare statement of physical flows and equivalent units of output for the period; 3. ascertain the total costs to be accounted for this period; 

4. calculate the cost per equivalent unit; 

5. apportion cost between finished output and work-inprogress; and 

6. check that all costs accounted for 

Similarities between process costing and absorption costing 

Both track the same manufacturing cost elements: DMs, DL, 

DEs and Mfg OhdsBoth involve WIP, FG and COGS 

Differences between process costing and job costing 

• No. of WIP accounts: PCS have many WIP accounts whereas 

JCS have one WIP account 

• Documentation to track costs 

JCS = job cost sheet 

• PCS = production cost report for each process 

• Point at which costs are totaled 

JCS - mfg costs totalled on completion 

• PCS - mfg costs totalled at fixed time intervals 

• Unit cost computation 

JCS - total job costs/no of units produced 

• PCS - total period costs/units produced in the period 

WIP and EQU/V ALENT UNITS 

Processes rarely deal with solely with completed units and therefore we need ‘to deal with output in terms of completed units and those still in the process at various stages of completion in the process. The notion of Equivalent Units enables work in process to be expressed in terms of completed output. 

Equivalent units may be defined as: A notional quantity of completed units substituted for an actual quantity of incomplete physical units, when the aggregate work content of the incomplete units is deemed to be equivalent to that of the substituted quantity of