Screen Printing
Screen printing is a printing technique where a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the open mesh apertures with ink, and a reverse stroke then causes the screen to touch the substrate momentarily along a line of contact. This causes the ink to wet the substrate and be pulled out of the mesh apertures as the screen springs back after the blade has passed. One colour is printed at a time, so several screens can be used to produce a multi-coloured image or design.
There are various terms used for what is essentially the same technique. Traditionally, the process was called screen printing or silkscreen printing because silk was used in the process. It is also known as serigraphy and serigraph printing. Currently, synthetic threads are commonly used in the screen printing process. The most popular mesh in general use is made of polyester. There are special-use mesh materials of nylon and stainless steel available to the screen-printer. There are also different types of mesh size which will determine the outcome and look of the finished design on the material.
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Why Use Screen Printing?
Screen printing is more cost-efficient compared to digital printing since it can create large quantities of the design at a faster turnaround pace. Higher volumes of identical graphics can be mass produced using the screen printing process, making this the best printing option to use for larger orders. This process is used mainly for T-shirts, Hoodies, Joggers and the like. Screen printing can be used to create a single color up to four color prints.
The design is created and the Screen is prepared
To start, the printer takes the design they want to create on the finished product, and prints it out onto a transparent acetate film. This will be used to create the stencil.
Next, the printer will choose a mesh screen to suit the complexity of the design, and the texture of the fabric being printed. The mesh screen is then coated with a layer of light-reactive emulsion, which will harden when developed under bright light.
The emulsion is exposed, washed off, stencil is created
The acetate sheet featuring the design is then laid onto the emulsion-coated screen, and the whole thing is exposed to a very bright light. The light hardens the emulsion, so the parts of the screen which are covered by the design remain in liquid form.
If the final design is going to include more than one colour, then a separate screen must be used to apply each layer of ink. To create multi-coloured products, the printer must use his skill to design each stencil, and line them up perfectly to ensure the final design is seamless.
After the screen has been exposed for a set time, the areas of the screen not covered by the design will have turned hard. Any unhardened emulsion is then carefully rinsed away. This leaves a clear imprint of the design on the screen for the ink to pass through.
The screen is then dried, and the printer will make any necessary touch-ups or corrections to make the imprint as accurate as possible to the original design. The stencil is now ready to be used.
The item is prepared for print, then printed
The screen is then placed on the printing press. The item or garment being printed is laid down flat onto the printing board, underneath the screen.
There are a number of different presses, including manual and automatic styles, but most modern commercial printers will use an automatic rotary carousel printer, as this allows several different screens to work at once. For multicoloured prints, this sort of printer can also be used to apply the separate colour layers in quick succession.
The screen is lowered down onto the printing board. Ink is added to the top end of the screen, and a squeegee is used to pull the ink along the full length of the screen. This presses the ink through the open areas of the stencil, imprinting the design on the product underneath.
If the printer is creating multiple items, then the screen is raised and a new garment is placed onto the printing board. The process is then repeated.
Once all the items have been printed and the stencil has served its purpose, the emulsion is removed using a special washing fluid so the mesh can be reused to create new stencils.
The product is dried, checked and finished
The printed product then passes through a dryer, which ‘cures’ the ink and creates a smooth, colourfast finish. The final product will be checked and washed thoroughly to remove any residue, before being passed on to its new owner.