What is Screenprinting?
Screenprinting is a process by which ink is forced though mesh fabric that has been stretched over a frame, onto a flat surface, to create a type of stencil printing. Print colours are applied separately via individual screens, so the final artwork is built up in layers.
The stencil on the screen can be made in different ways. We make the stencil by painting a light-sensitive emulsion onto the mesh, which is then developed by a process similar to developing a photograph.
This is a metal or wooden frame over which fine mesh fabric is stretched. We use aluminium frames and polyester mesh. The thread count of the mesh is very important and is determined by several factors, namely, the level of detail in the print, the type of ink to be used and the substrate that is to be printed.
To prepare a screen for printing , the mesh is coated with a UV sensitive emulsion which we then leave to dry in the dark overnight.
Preparing the Artwork
A separate screen is needed for each print colour, so first of all the artwork is separated into different layers by colour, either using Adobe Photoshop or Illustrator. Each colour is then converted to black (this gives us the best print definition) and we then make a positive acetate film for each screen/colour.
Exposing the artwork onto screen
The acetate film is then secured to the front of the screen and the screen is placed face down into a vacuum exposure unit. The screen is then exposed to UV light for a set period of time. Where the light hits the screen the emulsion changes its composition and becomes solid. Where the black design on the acetate film prevents light hitting the emulsion on the screen, the emulsion remains water soluble and does not solidify, so that after exposure it is washed away leaving behind a stencil image of the design. We then place the screen into a drying cabinet to harden the emulsion.
Once dry, each screen is attached to an arm of the screenprinting carousel and after carefull registration to ensure the screens are aligned correctly, they are ready for printing. Ink is then pressed through the screen using a rubber squeedgee. After each print application the print is ‘flash dried’ under a spot heater. When all the colours have been applied, the print is finally cured in a tunnel dryer.
For many years plastisol inks were a favoured choice for screenprinters as water based inks were difficult to use. While plastisol gives great print quality, it requires toxic chemicals for clean up so isn’t eco-friendly or sustainable. Water based inks have improved in recent years so they don't dry into the screen mesh as quickly and any residual ink can be washed down the drain without any adverse affect to the environment. We mainly use waterbased Permaset and Virus inks.