[Seth23665]

Hi, im new here and desperately need some help. I'm a graphic artist for a small company, have been doing freelance design/artwork for years but never been very involved in the screen printing process. Im the only employee in the art department here so when things dont print correctly it falls on me. I'm trying to learn as much as possible about color separations but every time i think im getting it right something goes wrong, and theres no one here to help me, and i received absolutely no training whatsoever (i explained several times before and after starting this job, that i have no experience with separations or printing)I'm not bashing my employer, just making it clear that I didn't lie about my capabilities to get this job. I can't afford to keep holding the press up so i need some in depth responses to this. The issue im having is that when a design comes along that requires various halftones, areas less than about 50 percent are not printing and i have no idea why. We hired someone to sep one of our designs several months ago, and i took a look at how he approached the design. I open the info window in photoshop and went through each channel and even some areas of his separations were as low as 9 to 15%, which was intentional. I've talked to other artist with experience and they have told me to sep certain areas as low as 10%. So I'm not understanding how these experienced artist are getting areas to print that low when i can't seem to get even 30% to show up. Please help!!

 

[Industryps]

You've got a tough one here...
It's hard to offer a solution without being able to see the issues, can you post a couple images?

Just some quick ideas that may help-

• Are you adjusting your halftone size (frequency) for the art? There is no default dot size, it varies from one design to another as to what size will hold the most detail.

• How are you printing the films used to make screens? If you don't have a high quality film positive, the smaller details will never make it to the screen used for printing. The black parts of the film need to be very opaque- when held up to a light, you should not see any light coming through the solid portions of the black

 

[Seth23665]

thanks for responding! i dont have the actual film, but here is a screen shot of the psd file as well as the same area after printed on a white shirt ( the color was red by the way). I wasn't even aware that i could adjust the halftone frequency. Would this be something i can adjust within photoshop/illustrator or would i need to do it in the rip software?

 

[Seth23665]

And im usually seperating the file in photoshop. saving, and then opening in illustrator to add reg marks. Then i file print, uncheck everything but process black. save to one of our networks, which saves the file as a postscript file. open it in our rip software and select rip and print

 

[Industryps]

Are you bitmapping your image in PS to get the halftone? You can adjust the frequency and angle there, or when you output from Illustrator, you can also halftone the image there in the "Separations" sub-menu that pops up.

Looking at your images, there also may the the issue of the screens themselves. For halftones, the screens need to be a high mesh count- (230 or higher) and coated with a thiner coat of emulsion than normal. These steps help ensure that your nice opaque film positive actually burns the image onto screen.

 

[Seth23665]

Thank you i really appreciate it. No one ever even remotely mentioned any of this so ill do some more research and try to figure out what frequency to fit my seps
Thanks!!

 

[Industryps]

Found a tutorial that may be helpful here and here

 

[ABM]

And im usually seperating the file in photoshop. saving, and then opening in illustrator to add reg marks. Then i file print, uncheck everything but process black. save to one of our networks, which saves the file as a postscript file. open it in our rip software and select rip and print

If you're sepping in PS you should keep it in PS for simplicity. Under the print function, you can check a box that will add reg marks or you may be able to add them within your rip software. If you need larger reg marks it would be better to create them in AI then drag them into the PS channels. When sending to your rip try using the Save As function and save as PSD or DCS2 EPS file but your rip software will dictate if this can be done or not. I'm not familiar with how you're printing from AI but that may be the issue or part of it.

In your rip settings make sure your LPI is 45-55. 45 is best for most halftones, 55 is generally for photographs or high detail art but still ok to use on a daily basis. The higher the number, the smaller the halftone dot. If your current setting is too high it's possible your dots are smaller than the holes in the screen mesh you're using, therefore, they get washed out, not held.

Bitmapping your art in PS is not the best way to get smooth halftones. Bitmapping is generally best if you're going for that comic book effect.

Other possibilities to consider are...
-screen mesh used
-emulsion used or how are high mesh screens being coated
-is the screen person washing screens out properly

If you have more questions I may have the answers. I've been doing this for 25yrs.

 

[bertiewooster]

All great advice above, I generally go with a 45lpi dot size but can also do 55lpi okay, I think Illustrator automatically outputs at around 65lpi which makes the dot size very small and will cause difficulty exposing. The screen exposure time for dots will always need to be lower than line art and as mentioned above around a 305 screen ( 120T here in the UK ) is best!
There are debates about the dot shape too, I like to use eliptical and set the angle to 25.
You can only access these settings in Illustrator if you have a rip and the ability to select separations.

 

[Seth23665]

thanks for all the advice! I checked an it looks like the main problem was illustrator automatically saving it as 70 LPI, which im now printing at 45, and so far everything has come out nicely! thanks for all the help. I have one more question, if I have a pms color that needs to be a bit darker in some areas, can i layer black over top of it at like 10% ? or should i lay the black down first and then color over top?
thanks!

 

[Industryps]

Black down first. Congrats on figuring it out!