Screen Printing Tip of the Week: Preventing Moiré Patterns

June 15, 2013 at 5:00 am 2 comments

Moire-pattern-1Heads up Screen Printers!!!  Kieth Stevens has a great tip on how to combat Moiré, a technique that even some seasoned printers don’t know about (as published in Impressions Magazine):

When printing halftones, a radiating pattern sometimes appears. This pattern, called a moiré, occurs when the pattern of the mesh or screen fabric conflicts with the pattern of the halftone line count.

Moiré also can be caused by the artwork’s patterns, or the interaction between the patterns and the substrate’s texture. Sometimes, the moiré pattern doesn’t appear until after the artwork is printed.

A common method for countering this pattern collision is to increase the mesh thread count by a factor of 4.5 times. For example, if the moiré pattern occurs when using a 55 line halftone count, you would increase the mesh thread count to 230. For the most part, this solution will work; however, using higher mesh counts to eliminate the moiré pattern can result in a white underbase that is less opaque.

Another strategy is to custom stretch the screen mesh at an angle that will eliminate or reduce the moiré prior to burning the screen. To do so, stretch the frame, put it on the stretcher and lay a mesh over it. Then, take the positive film that contains the halftone art and lay that down on the mesh as if you were placing it to burn the screen.

If you see a moiré pattern appearing between the mesh and the positive, rotate the mesh and leave the film in the position that you want to burn it. As you rotate the mesh, you will see the moiré pattern move and change. Keep rotating it until you see the moiré reduce to almost nothing. Lock down your mesh at this exact angle and leave the film in the proper position for printing.

Finally, place the positive back down on the stretched and adhered mesh and you should see that the moiré pattern is gone. Mark down on the mesh the location of the registration so that after you coat the mesh with your emulsion, you can once again place the film on the screen, tape it down and expose the image as you normally would.

Kieth Stevens is the Western regional sales manager for International Coatings. He has been teaching screen printing for more than 10 years and is a regular contributor to International Coatings’ blogs. For more information, visit iccink.com and read the company’s blog at internationalcoatingsblog.com.

International Coatings manufactures a complete line of phthalate-compliant screen printing inks, including a wide variety of whites, specialty inks, special effects inks, color matching systems, additives and reducers.  For more information on our products, please visit our website at www.iccink.com.

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Entry filed under: General, How-To, Printing Tips. Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , .

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2 Comments Add your own

  • 1. Sticker Printing Online  |  July 4, 2013 at 12:40 am

    I found this informative and interesting blog in which you have written beautifully about the negative impact of Moire patterns. You have explained Moire patterns first and then it’s negative effect and at the end how to prevent it while doing screen printing. But you have said moiré patterns does not appear until after the artwork is printed but in some cases I have took notice that moiré patterns appear even before the artwork printing.

    Reply
    • 2. International Coatings  |  July 5, 2013 at 10:12 am

      Yes, you are correct. For example, the image we included on the blog shows a Moire pattern which formed when we put a film positive over screen mesh – before it was burned onto the screen. In this case, the Moire pattern occured when the halftone dot pattern clashed with the screen mesh pattern.

      Reply

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