!! To be fully written up with my photos of the process and inspiration, and more of the challenges, linked to Printmaking blog.
What is screenprinting? Types and technique
Screen printing is a printing technique whereby a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil.
There are various terms used for what is essentially the same technique. But they all have the following in common:
- Use of a frame (generally wood or aluminium) on which a mesh is mounted under tension. The mesh can be of different types: eg silk, polyester, nylon or metal and of varying degrees of fineness depending on the type of surface to be printed.
- A stencil is formed on the mesh by blocking off parts of the screen in the negative image of the design to be printed; that is, the open spaces are where the ink will appear on the substrate. The stencil can be made through different techniques: direct stencils made with photoscreen techniques or using masking solutions and indirect stencils used as masks.
- Mesh/frame preparation: The surface to be printed (commonly referred to as a pallet) is coated with a wide ‘pallet tape’ to protect the ‘pallet’ from any unwanted ink leaking through the screen and potentially staining the ‘pallet’ or transferring unwanted ink onto the next substrate. Next, the screen and frame are lined with a tape. The type of tape used in for this purpose often depends upon the ink that is to be printed onto the substrate. These aggressive tapes are generally used for UV and water-based inks due to the inks’ lower viscosities. The last process in the ‘pre-press’ is blocking out any unwanted ‘pin-holes’ in the emulsion. If these holes are left in the emulsion, the ink will continue through and leave unwanted marks. To block out these holes, materials such as tapes, speciality emulsions and ‘block-out pens’ may be used effectively.
- A blade or squeegee is moved across the screen to fill or ‘flood’ the open mesh apertures with ink, and a reverse stroke then prints the image as the screen touches 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 are layered to produce a multicoloured image or design. Hinge clamps keep the screen in place for easy registration
I had started to use stencil screenprinting in Printmaking 2 as a supporting technique in:
- Project 5.2: Arcadia Recycled to create the design for the collagraph plate
- Assignment 5: The Dreaming to create the design that first inspired the concept
See also tutorials etc on my Printmaking blog: http://print.zemniimages.info/screenprinting/
Photoscreen: Preparing photographic positives
To prepare photographic positives for photoscreen and photolithography all digital images or photographs need to be converted to greyscale and printed in black ink only onto transparent film using an inkjet or laser printer. If an image contains greys it is better to darken them as they are likely to overexpose and not show up in the print.
- Image sizes:Image resolution: 300ppi.
- Plate sizes: A3 37x45cms allow 6cms border so height 39cms and constrain proportions. A4: 38×25.3cms
Use CMYK? 8bit. Convert to bitmap. Output 700dpi. Method Halftone screen OK. Frequency 47 lines/inch, angle 30 degrees, Shape round.
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