The Screen Print Column
Solving the mystery of moiré G
Last month, Jason Chapman, director of operations at The Regency Group, New York, looked at the artwork, film and stencil attributes of moiré. In this article he expands knowledge into printing half-tones and gradients.
enerally, the white screens are used to improve opacity of bright colours on darker substrates.
A base white + colours + highlight white for example, is a typical arrangement and is very successful as a rule. Where printers are looking for more detailed and finer printing (smaller dot count) and enhanced definition for example photo realistic screen printing, whites or other base colours can be reconfigured at separation stage to give various outcomes such as levels of white and soft fades.
Let’s take the example used in last month’s article to keep the content flowing.
Eight colours which includes 3x whites, a grey, yellow, red, blue and black.
The colour sequence on the machine for this is also non-standard using less flash cures than would expect. Here’s the sequence: 1) White 1.
a. This would be a full white
which extends the furthest in the background and will be the softest edges of the smoke.
b. The ink would be a 50/50 white/ transparent or 50% opaque.
c. Using thinner blends of ink will help pass through all dots in the screen, whereas thicker ink may not and then create its own version of moiré. Like mesh threads clashing and blocking the halftones, ink not passing through, will also giving undesirable results.
2) White 2.
a. This white is printed wet-on-wet to soften the first white even further.
b. Printed as an 70%/ 30% clear opaque ink under all the bright colours as you would a normal white base except, not extending fully in the background but created to give another shade to the smoke.
c. Check that the ink mix is not creating any patterns moiré, if so, let the ink down further.
3) Flash cure – This would take very little drying due to it being on a 120 mesh.
4) White 3.
a. This is optional, but I like the third white to strengthen the highlights (like a standard highlight white). b. This white is not in the background but is in the smoke and hair around the face. The separation was sharpened to give harder lines this time. 5) Flash cure. 6) Cool Grey 6c – This screen is doing lots of things. a. Giving the smoke, hair and background more depth and shading.
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You can also relate the yellow and red overlaps to the flesh tones in the full image and the white highlights. Not only do we have over lapping of layers when printing this type of print, but also the additional shading created by the half- tone dots as well as adding the blue and black screens. In summary when you have perfected separation, film output, screen making and ink viscosity when using fine meshes, you can apply the same standards time and time again, avoiding moiré and printing those blends and shades that will blow the minds of your clients.
February 2025 | 75 |
You can get a sense of how many shades of yellow and red are created by placing the colours on top of the layers of white and grey by the image below which was a random test created in Photoshop.
b. Creating shading for all colours, especially skin tones. c. Providing some opacity for the blue in the suit, but only around 15% to allow the colour to be seen on the black substrate. 7) Flash cure. 8) Yellow 7404c. 9) Red 185c. 10) Blue 275c. 11) Black.
Colours
You may feel that this is just CMYK on whites, however, these are spot colour separations, and the actual tone of colours selected according to the design.
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