Screen printing


-:Screen printing :-

The role of a textile designer is to prepare designs for arnamentation of fabrics. Screen printing is one of the most specialized techniques of creating wonderful design on textiles. In this unit, we will be studying the screen printing technique for surface designing. So that screen - printed fabrics,as shown in can be produced.

Introduction:-

Printing done with screens is called screen printing. Screen printing is an innovative technique for surface designing , which today has a good market potential .
In the older time it was pursued as a hobby. Which had a very good business potential due to exclusive items designed by screen - printing. Besides designing on the fabric, screen printing offers potential for other surfaces like plastics, papers, walls, posters etc. Making item such as banners, logos, clothing, bed linen, table linen, and soft furnishings etc.

Screen printing is a simple ornamentation technique of surface designing for embellishment of fabric with the help of a simple stencil or screen through which colour is passed ,with a design on its surface. Process is a very widely used in India for creating attractive designs. The technique enhances creative ideas and can work with a wide range of colours patterns and styles.

The basics of screen printing :-

What is screen ?

Screen is generally made with frames. The frame serves the purpose of holding the bolting cloth or silk screen in a tight position as a basin for holding the paste while printing. The frame is usually of rectangular shape and its size has to be a few centimetres more than the size of the print desired. There is no hard and fast rule about this. The idea is that sufficient paste is held at one end ,to be taken to the other by the squeegee, covering the entire area to be printed.
The frame must be made of good quality seasoned ,knot - free wood. Metal frames are mostly used where rigidity is necessary for quality production e.g in mechanised screen - printing.
  • Screens may be made using cotton organdie stretched on a wooden frame. Such screens are very primitive, but for a beginner they are adequate. For professional use polyester mesh 

Bolting cloth

  • Is sold by the meter by screen - printing suppliers.this is a fine gauze mesh of man - made fabric. Earlier the mesh used to be made of silk hence the term 'silk screening'. Which is still in common use today.
Mesh numbers can range from very coarse (30) to fine (90) and then to ultra fine. The numbers indicate the number of threads per 2.5 cm(1. Inch) screens using higher mesh count fabric produce very sharp prints with small and fine details. The paste consumption will also be less, and reverse the case with screens of lower mesh counts. Good quality printing will result from a properly stretched and prepared screen,espe especially when multi - colours are used in the process,so prime importance should be given to this aspect during screen preparation.
  • A blade of rubber or plastic is attached to a wooden handle and used for pushing the printing paste over the surface of the mesh .it is the pressure that is applied to the squeegee that pushes the printing paste through the mesh and onto the fabric beneath.
  • The squeegee selected for a particular job should be at least 1.5" wider than the width of print or design taken in hand. Also its width should than the inside width of the frame by about the same margin of 1.5".This will allow for side play of squeegee inside the frame while printing is carried on.

Squeegee

  • The rubber used for marking this tool should have appropriate flexibility or hardness and be resistant to the various chemicals in the printing paste.the higher the hardness, the less flexible the hardness,the less flexible the squeegee will be, and so will require more pressure. This can,however,give finer and sharper prints. The squeegee blade should be maintained and trimmed with a sharp square edge. A through cleaning is necessary after each printing job when sturing it for subsequent use. A piece of sand paper nailed to a block of wood will help to sharpen the rubber edges when they become round and blunt in course of time.


What is screen printing ?

Screen - printing is a process ,which looks very complicated at first,but is actually very simple once you make a start. A versatile printing technique that is widely used ,it can be applied to a wide variety of patterns or to almost any surface from bottles and circuit boards to wallpaper and textiles. It's basic principles are simple. To begin with,a screen is made by stretching fabric on to a frame. There are different screen bolting fabrics that may be used - from silk and nylon to polyester and organdie.The framing material is usually wood or tubular aluminium which is designed to secure the fabric.
Once the fabric is stretched and attached to the frame,a stencil is required to complete the screen. Blocking out partions of the screen fabric and leaving other areas open produces a stencil. The areas left open allow print paste to pass through the screen which results in a printed image.

Features of screen printing:-

  • It is simple to operate and does not require expensive equipment. New patterns can be developed quickly and without initial experience. Screen can be produced, cheaply, e.g a 12"×14" wooden frame may cost approximately RS.18.
  • A variety of fabrics can be printed easily.
  • This method is economical in production and less labour oriented than block printing.

Bright & clear prints

  • Larger repeats are possible .
Many colours can be used.
  • Prints are brighter and more intense and appear natural
  • Sharp lines, effects and fine mesh effect can be produced easily.

-:Types of screen printing:-

1- manual screen printing

In manual screen printing the fabric to be printed is laid on a long table.  A screen with length slightly greater than the fabric width is fitted in a wooden frame. The design to be printed is transferred to the screen ( for each colour,there is a separate screen) and the space in the screen not covered by the design is covered with an impermeable membrame so that the colouring material ean only pass through that part of the design which is to be in one colour.
A thick paste containing the colour (dye or pigment) prevents migration of the colour and the paste holds the colour till it is fixed after printing and then the unwanted paste ingredients can be removed. For this appropriate thickening agents are used which increase the viscosity of the paste.

Screen frame

The printing paste is pressed through the screen with the help of a device having a rubber blade called squeegee the screen is moved one repeat and the process repeated. The different colour screens fallow and thus the whole lenghl of the fabric is printed.

Manual screen printing process


-:Semi - automated screen printing:-

The manual process has been sequtomated by mounting the screen on a carriage and driving the squeegee mechnically across the screen

Semi - automated screen printing


In both hand and semi - automatic flat screen printing the colours are printed one after another with time for drying between one colour and the next. The dried fabric is removed from the table and stored for a while before fixing by dry heat in the case of pigment printing and steaming or dry heat in case of reactive dye printing.

-: Automated flat bed screen printing:-

In order to increase the speed of flat screen printing,it was imperative to devise a method of printing all the colours simultaneously. This entails each colour application position being fixed while the substratemoues. The colour is applied through the screens while the frame is stationary.

Fully automated flat screen printing machine

Flat bed screen printing machines where the fabric remains stationary and the screen moves on a carriage have also been developed for the printing of silk. The entire operation is controlled pneumatically.one such machine is shown in.

Automated rotary screen printing:-

Unlike flatbed machines, in which the printing action is intermittent,continuous movement of the fabric has been achieved in rotary screen printing machines

Rotary screen printing set-up

This is by moving the screens along with the fabric while printing. The screens are cylindrical and the fabric also moves on a cylinder. However, these machines are quite expensive.

Rotary screen printing

  • Screen printing is a simple ornamentation technique of surface disigning for embellishment of fabric with the help of a simple stencil or screen through which colour is passed, with a design on its surface. This process is a very widely used in India for creating attractive designs. The equipments can be automatic, semi - automatic or manual. The manual process is very popular in India and provides job to large number of people. It is of utmost importance that the right tools and the right process are used to create designs on fabrics.

This lesson deals with the following aspects of screen printing :

  • Tools used in screen printing.
  • Fabrics that can be used for screen printing.
  • The printing paste.
  • Mixing of colours.
  • Marking the fabric before printing.
  • Preparation of screen/screen coating method.
  • Cleaning the screen.






Written by:- RASHMI JADAUN




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