A screen is made from a piece of penetrable, finely wove fabric called mesh stretched over a frame of aluminum or wood. Originally human hair then silk was woven into screen mesh ; now most mesh is made from synthetic materials such as steel, nylon, and polyester. Areas of the screen are closed off with a non-permeable material to form a stencil, which is a negative of the image to be published ; that is, the open spaces are where the ink will appear.
The screen is placed on top of a substrate like fabric or paper. Ink is placed on top area of the screen, and a fill bar ( often referred to as a floodbar ) is used to fill the mesh openings with ink. The operator starts with the fill bar at the back of the screen and behind a reservoir of ink. The operator lifts the screen to stop contact with the substrate and then employing a slight quantity 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 back of the screen. The ink that’s 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 proportionate to the thickness of the mesh or stencil. As the squeegee moves toward the back of the screen the stress of the mesh pulls the mesh up away from the substrate ( called snap-off ) leaving the ink on the substrate surface. There are three common kinds of screenprinting presses. The ‘flat-bed ‘, ‘cylinder ‘, and the most generally used type, the ‘rotary ‘. Textile items revealed with multi-colour designs frequently employ a wet on wet method, or colours dried while on the press, while graphic items are permitted to dry between colors that are then broadcast with another screen and often in a different colour after the product is re-aligned on the press.
The screen can be re-used after cleaning. However if the design isn’t required, then the screen can be “reclaimed” ; that is, cleared of all emulsion and used again.
The reclaiming process involves getting rid of the ink from the screen then spraying on a stencil remover. Stencil removers come in the shape of liquids, gels, or powders. The milled types need to be mingled with water before use, and so can be considered to be part of to the liquid class. After applying the stencil remover, the emulsion must be washed out employing a pressure washer. Most screens are prepared for recoating at this time, but occasionally screens must bear another step in the reclaiming process called dehazing. This extra step removes haze or “spook photographs” left at the back in the screen once the emulsion has been removed.
Ghost pictures have a tendency to faintly outline the open areas of prior stencils, therefore the name. They’re the results of ink remains besieged in the mesh, frequently in the knuckles of the mesh ( the points where threads cross ).
While the general public thinks of duds with screenprinting, the strategy is employed on many thousands of items, including decals, clock and watch faces, balloons, and plenty of other products. The strategy has even been changed for more advanced uses ,eg laying down conductors and resistors in multi-layer circuits using thin ceramic layers as the substrate.