There are three main tools used in screen printing: the screen, the screen printing squeegee and the ink. The screen acts like a stencil, and defines the image that is to be produced onto the surface. The screen printing squeegee is used to spread the ink evenly over the screen to make a clean print on the surface.
There are two main functions of the squeegee for screen printing, defined by factors like composition, size and form, angle, pressure, and speed of the squeegee. These in turn determine the quality of the impression made by the squeegees. The two most vital functions of the screen print squeegee can be defined by two strokes: the flood and the print.
The flood stroke is considered by many to be merely a preliminary step in this process. However, experts have made it a regular and indispensable part of their routine. The flood stroke pre-loads the stencil mesh with ink, hence preparing it for the print. This pre-loading makes the print stroke much easier, especially while transferring the ink onto the surface to be printed. Very little pressure is applied to the squeegee at the flood stroke: just enough to move the ink, but not enough to make a print. It is a better idea to lift the screen off the substrate to avoid accidents, since even experts cannot specify the exact pressure to apply during this process. This stroke becomes vital while using volatile inks or while printing in a hot/dry environment. It takes only a few seconds and helps avoid wasted prints and disruptions in the process, and hence, the flood stroke becomes quite an investment in the long run.
The actual job comes in at the print stroke, which has three main functions. It is one squeegee movement across the screen, but it connects the mesh to the surface, it inks the screen, and furthermore, it moves the extra ink off the centre and into the inkwell.
The downward stroke closes the distance between the mesh and the surface to be printed, putting extra tension on the mesh. This tension in turn drags the mesh onto, and then off of, the surface substrate. This interplay results in a very distinct and clear cut final image.
As the squeegee moves ahead, it washes a wave of ink before it, which pushes it through the mesh and down to the substrate. Further forward movement of the squeegee stops all the ink that does not contribute to the imprint. This ink is deposited at the further end of the silkscreen for the prints that will follow. In this way, a screen printing squeegee is used to make prints on to any surface of choice.
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