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. 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. Screen printing
Screen printing is also a stencil method of print making in which a design is imposed on a screen of polyester or other fine mesh, with blank areas coated with an impermeable substance. Ink is forced into the mesh openings by the fill blade or squeegee and by wetting the substrate, transferred onto the printing surface during the squeegee stroke. As the screen rebounds away from the substrate the ink remains on the substrate. It is also known as silk-screen, screen, serigraphy, and serigraph printing. One color is printed at a time, so several screens can be used to produce a multicoloured 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 prior to the invention of polyester mesh. 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.
1.1 1960s to present
Screen printers use a silkscreen like this Screenstretch version, a squeegee, and hinge clamps to screen print their designs. The ink is forced through the mesh using the rubber squeegee, the hinge clamps keep the screen in place for easy registration
A. Ink. B. Squeegee. C. Image. D. Photo-emulsion. E. Screen. F. Printed image.
How to screen print one image
How to screen print with multiple layers using CMYK
Different samples of the printed image
Used to hold screens in place on this screen print hand bench
Trolley containing a wooden squeegee and acrylic ink
A wash out for cleaning screens
A screen is made of a piece of mesh stretched over a frame. The mesh could be made of a synthetic polymer, such as nylon, and a finer and smaller aperture for the mesh would be utilized for a design that requires a higher and more delicate degree of detail. For the mesh to be effective, it must be mounted on a frame and it must be under tension. The frame which holds the mesh could be made of diverse materials, such as wood or aluminum, depending on the sophistication of the machine or the artisan procedure. The tension of the mesh may be checked by using a tensiometer; a common unit for the measurement of the tension of the mesh is Newton per centimeter (N/cm). A stencil is formed 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. Before printing occurs, the frame and screen must undergo the pre-press process, in which an emulsion is 'scooped' across the mesh and the 'exposure unit' burns away the unnecessary emulsion leaving behind a clean area in the mesh with the identical shape as the desired image. The surface to be printed (commonly referred to as a pallet) is coated with a wide 'pallet tape'. This serves 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. The screen is placed atop a substrate. Ink is placed on top of the screen, and a floodbar is used to push the ink through the holes in the mesh. The operator begins with the fill bar at the rear of the screen and behind a reservoir of ink. The operator lifts the screen to prevent contact with the substrate and then using a slight amount of downward force pulls the fill bar to the front of the screen. This effectively fills the mesh openings with ink and moves the ink reservoir to the front of the screen. The operator then uses a squeegee (rubber blade) to move the mesh down to the substrate and pushes the squeegee to the rear of the screen. The ink that is in the mesh opening is pumped or squeezed by capillary action to the substrate in a controlled and prescribed amount, i.e. the wet ink deposit is proportional to the thickness of the mesh and or stencil. As the squeegee moves toward the rear of the screen the tension of the mesh pulls the mesh up away from the substrate (called snap-off) leaving the ink upon the substrate surface. There are three common types of screen printing presses. The 'flat-bed', 'cylinder', 'rotary'. Textile items printed with multicoloured designs often use a wet on wet technique, or colours dried while on the press, while graphic items are allowed to dry between colours that are then printed with another screen and often in a different colour after the product is re-aligned on the press. Most screens are ready for re-coating at this stage, but sometimes screens will have to undergo a further step in the reclaiming process called dehazing. This additional step removes haze or "ghost images" left behind in the screen once the emulsion has been removed. Ghost images tend to faintly outline the open areas of previous stencils, hence the name. They are the result of ink residue trapped in the mesh, often in the knuckles of the mesh (the points where threads cross). While the public thinks of garments in conjunction with screen printing, the technique is used on tens of thousands of items, including decals, clock and watch faces, balloons, and many other products. The technique has even been adapted for more advanced uses, such as laying down conductors and resistors in multi-layer circuits using thin ceramic layers as the substrate. Stencilling techniques
A macro photo of a screen print with a photographically produced stencil. The ink will be printed where the stencil does not cover the substrate.
A method of stencilling that has increased in popularity over the past years is the photo emulsion technique:
Hand-painted colour separation on transparent overlay by serigraph printer Csaba Markus
The original image is created on a transparent overlay, and the image may be drawn or painted directly on the overlay, photocopied, or printed with a computer printer, but making so that the areas to be inked are not transparent. Any material that blocks ultra violet light can be used as the film, even card stock. A black-and-white positive may also be used (projected onto the screen). However, unlike traditional plate-making, these screens are normally exposed by using film positives. A screen must then be selected. There are several different mesh counts that can be used depending on the detail of the design being printed. Once a screen is selected, the screen must be coated with emulsion and dried. Once dry, it is then possible to burn/expose the print. The overlay is placed over the screen, and then exposed with a light source containing ultraviolet light in the 350-420 nanometer spectrum. The screen is washed off thoroughly. The areas of emulsion that were not exposed to light dissolve and wash away, leaving a negative stencil of the image on the mesh.
Another advantage of screen printing is that large quantities can be produced rapidly with new automatic presses, e.g. up to 2139 shirts in one hour by a single operator. Materials
A caviar bead is a glue that is printed in the shape of the design, to
which small plastic beads are then applied – works well with solid
block areas creating an interesting tactile surface.
Cracking ink effect is when the ink produces an intentional cracked
surface after drying.
Discharge ink is used to print lighter colours onto dark background
fabrics, they work by removing the dye of the garment – this means
they leave a much softer texture. The cons with this process is that
they are less graphic in nature than plastisol inks, and exact colours
are difficult to control. One of the pros of using this process is
they are especially good for distressed prints and under-basing on
dark garments that are to be printed with additional layers of
plastisol. It adds variety to the design or gives it that natural soft
Expanding ink (puff)
Expanding ink, or puff, is an additive to plastisol inks which raises
the print off the garment, creating a 3D feel and look to the design.
Mostly used when printing on apparel.
Flocking consists of a glue printed onto the fabric and then flock
material is applied for a velvet touch.
Foil is much like flock, but instead of a velvet touch and look it has
a reflective/mirror look to it. Although foil is finished with a heat
press process it needs the screen printing process in order to add the
adhesive glue onto the material for the desired logo or design.
Four-colour process or the CMYK colour model
Four-colour process is when the artwork is created and then separated
into four colours (CMYK) which combine to create the full spectrum of
colours needed for photographic prints. This means a large number of
colours can be simulated using only 4 screens, reducing costs, time,
and set-up. The inks are required to blend and are more translucent,
meaning a compromise with vibrancy of colour.
Glitter or Shimmer ink is when metallic flakes become an additive in
the ink base to create this sparkle effect. Usually available in gold
or silver but can be mixed to make most colours.
Gloss ink is when a clear base laid over previously printed inks to
create a shiny finish.
Metallic ink is similar to glitter, but smaller particles suspended in
the ink. A glue is printed onto the fabric, then nano-scale fibers
applied on it. This is often purchased already made.
Mirrored silver is a highly reflective, solvent-based ink.
Nylobond is a special ink additive for printing onto technical or
Screen with exposed image ready to be printed.
Printed electronics, including circuit board printing
Signs and displays
Semiconducting material In screen printing on wafer-based solar photovoltaic (PV) cells, the mesh and buses of silver are printed on the front; furthermore, the buses of silver are printed on the back. Subsequently, aluminum paste is dispensed over the whole surface of the back for passivation and surface reflection. One of the parameters that can vary and can be controlled in screen printing is the thickness of the print. This makes it useful for some of the techniques of printing solar cells, electronics etc. Solar wafers are becoming thinner and larger, so careful printing is required to maintain a lower breakage rate, though high throughput at the printing stage improves the throughput of the whole cell production line.
Used to hold screens in place on this screen print hand bench
Dye Gocco Ink jet Printed electronics Printed T-shirt Printing Roll-to-roll printing Seriolithograph Svecia screen printing machines Textile printing
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Kiddell, Peter: Screen
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