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How to achieve 100% opaque black to correctly print on screen printing film


Good file preparation is essential for obtaining a black that is 100% opaque on the film, so as to enable a perfect exposure of the screenprinting frame. Here’s what to do.

In screen printing, the preparation of the design, normally called the “pre-printing phase”, is fundamental. 

Screenprinting is a process whereby all the different elements affect one another, making it a sequence of interconnected steps. If every single one of them is carried out to perfection, the final result will be exactly what you were looking for.

We get many requests for assistance from customers who need help understanding how to obtain opaque black, i.e. a black that prevents the light from the exposure unit from going through the film and drying the emulsion. This is the only way you can be sure that the design’s details will be printed correctly.  

Indeed, while the frame is being exposed, the light passes through the film wherever it’s not “blocked” by the black, and therefore the emulsion solidifies in the areas where the black isn’t present. 

Conversely, therefore, any areas where the black layer is thick, solid and impenetrable, the light will not pass through the film. In technical jargon it’s called “100% black”.

Here’s a short step-by-step tutorial to obtaining 100% black, a procedure that can be followed with the most commonly used graphics software programmes: Adobe Photoshop and Illustrator.

If using Adobe Photoshop:

– press the F8 key to open/close the Info panel

– if the colour mode is RGB/CMYK, click Image -> Mode -> Grayscale

– check the black percentage in the Info panel. If necessary, change the tonal values to obtain 100% black.

If using Adobe Illustrator:

– use the F6 key to open/close the Color panel

– if the line/shape is in CMYK or RGB mode, you can change it to greyscale by selecting the object and clicking Edit -> Edit Colors -> Convert To Grayscale

– change the black settings in the Color panel to get 100% black.

Now the file settings are correct.

To obtain a completely opaque black on the film, it’s necessary to use a suitable printer with the correct settings.

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