How to Expose a Plate With a Halftone?

Printing plate or a cliché is a key element in pad printing, which allows printing to three-dimensional surfaces. The most commonly-used printing plates are manufactured with steel or plastic. Unlike steel plates, plastic plates need to be exposed with a halftone screen or a film. The halftone screen controls the etching depth, which regulates the amount of ink entering the etched area. Exposing your plate with halftone requires few essential steps.

Things You'll Need

  • Film
  • Printing plate
  • Platemaker
  • Halftone pad-printing plate screen
  • Soft bristle brush
  • Toaster oven or plate dryer
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Instructions

    • 1

      Cut the film so that it fits the plate.

    • 2

      Place the film over the plate. Before placing the plate over the film, peel off the protective coating from the plate and inspect it for defects, such as bubbles. The film should be placed on the side of the plate from which you removed the protective cover.

    • 3

      Close the platemaker glass over the plate. Keep the film securely in position on the plate. If you are using a vacuum frame, turn the vacuum on.

    • 4

      Expose the plate by turning on the platemaker. Expose the plate from one to two minutes or according to the manufacturer's protocol.

    • 5

      Remove the film and place a halftone-exposure screen over the plate. Several halftone-exposure screens exist -- which differ in the number of dots that exists in a linear inch -- in the shape of the dot and the tint or screen-dot range indicated as percentage. For example, a halftone screen that has an 85-percent tint allows 15 percent light transmission through. The higher the tint, the more area is protected from light, which corresponds to higher ink laydown. Consult the manufacturer for proper halftone screens.

    • 6

      Close the platemaker glass over the plate and halftone screen. Expose the plate for 40 seconds or as recommended by the manufacturer.

    • 7

      Remove the halftone screen.

    • 8

      Remove the plate and place it into a container with room-temperature water. Rub the plate lightly with your fingers or a soft-bristled brush. Finish the plate-washing as soon as the image is visibly in the plate surface.

    • 9

      Dry the plate in a toaster oven or plate dryer at 70 degrees Fahrenheit for 15 minutes or according to the manufacturer's protocol.

    • 10

      Place the plate to the platemaker and expose for an additional 15 minutes. This post-exposure will harden the polymer surface.

    • 11

      Remove the plate from the platemaker and use it for pad printing.

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