I've got a problem with my halftone dots and I'm not sure how to fix it. I'm burning screens with a lumitron x-unit (fluorescent blacklights) 45 lpi at 22.5 degrees on a 260 mesh for 5 minutes. If I do a fade, I'm getting a sort of wavy pattern toward the outer edge of the halftones, if I do a uniform 25 - 50% "tint" everything is fine...even on a 200 mesh. Hopefully you can see what's going on in the picture. I'm using Chromaline UDC-HV emulsion. Is the angle of the dots wrong??? Thanks for any advice!
Yes, I'm using a vacuum. The positive looks beautiful....I'm using dmax 4 GO waterproof film and they come out real black. I tape the positive to the ink side.
It's not a good picture, but the halftones look flat to me, I can't see any gradient and certainly not to 0%.
It looks like the halftones are not washing out properly - is that true or a trick of the photo?
What printer/ink are you using?
Sorry about the bad photo, I was holding the screen with one hand and the camera with the other.
That's the way the halftones are washing out, it's like the film is puckering or something. I'm using an epson R1800 with just dye based ink and fast RIP software. I'll try to get a better pic of the screen.
My thought would be its not washed out all the way also. I have this issue fron time to time. usually just change my burn time and pay more attention to the wash out and it goes away.
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Here is another pic.....when you say a real halftone image do you mean just a photo printed from my rip printer. I don't have any samples from another company or anything. When I wash it out, it takes a pretty good blast, not full force from the pressure washer but a fairly strong stream.
What kind of film are you using? Some of the water proof films will cause a wavy look on you positive. I had this problem and used a square dot instead of an ellipse dot. The square dot made it stop but they are very hard to hold on an exposure.
I'm using Graphics One dmax4 waterproof film....you know you might have something there Joe because I started using it not too long ago and now I'm having this problem, Thanks!! And thanks to everyone that responded! I'll have to mess around with different dot shapes or just use index color with diffusion dithering in photoshop.
Looks to me like the halftone is disappearing around 30% or so...might be undercutting which means there is not enough distance between your blacklights and the glass on the unit...at least not enough distance for that much detail. Try cutting down exposure time by 30 sec. - 1 min. just to see if you can hang on to a little more detail.
weird halftones 
