Today, screen printing is the heart and soul of many bulk printing operations. It first rose to popularity in the 18th century, when it became easy to import silk mesh - a key component of screen printing - from the East. In the 19th century, screen printing became prevalent in the advertising world, and from then on, it has been used widely across many industries, including retail and electronics due to the easy customisation possibilities it affords.
While screen printing can be manual - especially used when there are only small print runs required - it is very often automated, using advanced inks and materials in combination with computer technology to mass print. One of the biggest advantages of screen printing is that it can print on almost any kind of surface, be it fabric, paper, glass, wood, card, plastic or leather. In this article, we will discuss the screen printing process, its uses, types, and benefits.
What is Screen Printing?
Screen printing, also known as silk screening or silkscreen printing, is the process of transferring a stencilled design onto a surface using a mesh screen, ink, and a squeegee (a rubber blade). The basic process of screen printing involves creating a stencil on a mesh screen and then pushing the ink to create and imprint the design on the below surface. The most common surface used in screen printing is paper and fabric, but metal, wood, and plastic can also be used. It is a very popular technique because of many reasons, but the most compelling reason is the vast choice of colours that can be used.
How Does It Work?
Screen printing can be done by hand or using a machine but the basic process is always the same. The differences can be of the type of ink used, its rendered effect and the printed surface. Below is the screen printing process step by step:
STEP 1. DESIGN CREATION
The first step in the process of screen printing is to create the design. Once a design has been decided upon, it is printed onto a transparent acetate film, which will then be used to create the screen or stencil.
Screen Printing Design Creation
STEP 2. SELECTING AND PREPARING THE SCREEN
When the design is all set to go, it is time to select the screen and mesh count. Mesh count is the total number of fibres in one square inch. Which mesh count you need will depend on the design being printed:
A higher mesh count can print finer details while preserving a fair coating of ink
Screens with a low mesh count let the ink flow through due to wider openings
After the mesh screen is selected, it is coated with a light-reactive emulsion layer.
Generally, there are three main types of emulsion:
Diazo: Cheaper, needs a longer exposure, not suitable for detailed prints.
SBQ-based: No mixing needed, cures extremely quickly, expensive, suitable for detailed work.
Dual-cure emulsions: Combination of Diazo and SBQ, requires mixing, overall cure time is less than Diazo, price is lower than SBQ.
STEP 3. EXPOSING THE EMULSION
The transparent acetate film is placed on the emulsion-coated mesh screen carefully under a bright light which causes the emulsion to harden and develop. It must be noted that when multiple colours are involved in the design, separate screens must be used for different colours.
STEP 4. STENCIL CREATION
Exposing the screen for a specific time will harden the uncovered areas of the screen, and the remaining unhardened emulsion, if any, will be rinsed away to leave a clear imprint on the screen. The screen is then dried, and if there are any touch-ups required, it will be done by the printer to make the imprint as close to the original design as possible. Now, the stencil is ready to be used.
STEP 5. PREPARATION FOR PRINT
The material to be printed is placed flat on the printing board, and the screen on top of the material in the desired position, ready to be printed.
Screen Printing Preparation
STEP 6. APPLYING THE DESIGN
In this step, the printed design will come to life. The screen is lowered down to the printing board. The desired colour ink is added to the top of the screen. A squeegee will evenly distribute the ink along the length of the screen. The ink presses through the open areas of the stencil and transfers on the underlying silk, consequently printing the design on the product.
The stencil will have served its purpose once all the items are printed. A special washing fluid is used to remove the emulsion to reuse the mesh for creating new stencils.
removing emulsion using washing fluid
STEP 7. HEAT CURING & FINISHING
Lastly, the printed product is heat-cured by passing through a dryer, creating a smooth design. This is done so that the design does not fade away.