Screen Printing Techniques: A screen is ready of a piece of spongy, finely woven fabric called mesh fix with stretched over a wooden blocks or aluminum blocks. Formerly human hair then silk was woven to construct a screen mesh; presently most mesh is woven of man-made materials such as nylon, steel and soft polyester. A screen Areas are blocked off with a non-permeable material to make a stencil, which is a negative of the picture to be printed; that is, the open areas are where the ink will come out.
The silkscreen is located atop a substrate such as paper or fabric. Ink is placed on peak of the screen, and a fill bar (also known as a flood bar) is used to fill the mesh openings with ink. The screen printer starts with the fill bar at the bring up of the screen and behind a tank of ink. The printer lifts the screen to stop contact with the substrate after this, then using a slight quantity of downward power pulls the fill bar to the front of the active screen.
Mesh Openings with Ink
This effectively fills the mesh openings with ink and travel the ink reservoir to the front side of the screen. The printer then uses a hard rubber blade which is known “squeegee” to move the mesh downward to the substrate and drags the squeegee to the rear of the silkscreen. The ink that is in the unblocked mesh is pumped or squeezed through capillary work to the substrate in a controlled and prescribed quantity, i.e. the damp ink deposit is comparative to the thickness of the screen’s mesh and or stencil. As the squeegee drags toward the rear of the screen the stress of the mesh pulls the mesh up away from the substrate (called snap-off) exit the ink upon the substrate places.
There are 3 common kinds of screen printing process. The flat-bed, rollering and the most generally used form, the ‘rotary’.
Always Textile printable stuff printed with different color designs often employ a wet on wet method, or colors dried while on the press, while graphic stuff are permitted to dry between colors that are then printed with more further screen and often in a dissimilar color after the result is re-aligned on the press for next working.
The screen can be re-used after washing the stencil
So if the design is no longer required, then the screen can be “reclaimed”; that is, cleaned of all emulsion and used once more. The reclaiming procedure involves cleared the ink from the used screen then spraying on a stencil cleaner. Stencil or emulsion removers come in the sort of liquids, gels, or powders. The powdered kinds have to be mixed with water before apply, and so can be measured to relate to the liquid type. After applying the stencil cleaner, the emulsion should be washed out using a pressure washer.
After this stage your screen is ready for re-using, but sometimes screens will have to feel a more step in the reclining procedure called dehazing. This extra step removes mist or “ghost images” left behind in the screen formerly the emulsion has been washed out. Ghost images tend to weakly outline the unblocked areas of preceding stencils, so the name. They are the out put of ink residue attentive in the mesh, frequently in the knuckles of the mesh (the holes where threads cross).
While the people thinks of fabrics in conjunction with screen printing, the technique is applied on tens of thousands of things, including decals, wall clock and watch faces, balloons and more further products. The technique has even been modified for more superior uses, such as laying down conductors plus resistors in different layer circuits using skinny ceramic layers as the substrate.
http://www.youtube.com/watch?v=TCIQsbdwaWY