How do you alleviate the crosshatching of the screen when printing a half tone gradient?
Hi, I'm trying to screen print an image on t-shirts with a gradient type half tone in it, and we keep getting the crosshatching of the screen itself in that section of the print. (We've tested a print on paper with the same results, so we know it's not the fabric creating the lines.) The problem area represnts a distant light source, which then diffuses into half tones as it spreads out. The distant light source is white, and the background red. We're printing on a white shirt, so we're using red ink for the background, with the white diffused light left blank and the shirt showing through. I'm in a third world country so communication, and technical expertise has not always been easy to come by, which has turned this into a bit of a problem. I don't know much about screen printing, but I'm learning some as I go, and I'm wondering if there is an optimal screen mesh count for this, and whether it would work better if we print the red background solid underneath, and print the dots of the white diffused half tone on top. Any assistance would be greatly appreciated. Thanks much, Philip
Last edited by Nashphil; August 17th, 2007 at 11:34 PM.
Reason: Change title
Re: How to alleviate the crosshatching of the screen when printing a half tone gradient
Well if the paper proof is bad then the art must be bad from the get go. If the art is bad there is nothing you can do but correct the artwork... welcome to redo.
Re: How to alleviate the crosshatching of the screen when printing a half tone gradient
I actually think its a quite common effect and the angle of the halftone is the remedy. Fluid or Solmu would be able to give you a solution. I think its called a moire effect that happens between the screen and the halftone. You might google up moire effect.
Re: How to alleviate the crosshatching of the screen when printing a half tone gradient
The original post states that it prints that way in paper proof. If it is moire than it is not the screen angle. It is the screen mesh count. A good rule of thumb is the lpi of the halftone x 4 plus one. Hence a 65 lpi x4 is 260 mesh plus one 305 mesh.
Further the angle can make a difference but then again so can the shape of the dot and further beyond that you can mount the screen on the frame at a 22 degree angle if you really want to get down and bad with yourself.
Another instance when I do 4 color process my angles most of the time are cyan 22.5, magenta 52.5 yellow 87.5 black 87.5. using an eliptical dot.
If I am dropping in a spot color the angle is set to match the angle of the color closest to the spot color ie orange spot could be either 22.5 or 52.5 degrees.
Re: How to alleviate the crosshatching of the screen when printing a half tone gradient
Hi, thanks for your help. The print at this point is only the single color red, on a white shirt. I've looked at the screen and transparancy more closely, and the tranparancy looks really good. The crosshatching is on the screen, but not of the screen. I'm in Bali and was told that the screen is a 99T, but also that this was the recommended screen for halftones. Hopefuly they work the numbers differently here, and 99 is not the mesh count. It appears to have come about in the process of transferring the transparancy to the screen. Everything has now been taken to a company called Crown, who supplies the screens and ink here on Bali. Hope they can make a good one. I've included a copy of the paper print. Any suggestions would be greatly appreciated. Thanks Philip
Re: How to alleviate the crosshatching of the screen when printing a half tone gradient
Change the halftones to somewhere between 30 and 45. You should be fine with a larger dot size with this art and still look good. Easier to burn and manage when printing as well. Change your angle to 25°
Also use the Elliptical dot pattern.
That crosshatch patter is due to a bad burn. You did not washout the image 100%.
Go to a higher dot size/pattern or lower your burn time to get a better/correct burn
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How do you alleviate the crosshatching of the screen when printing a half tone gradient? 
