There is often an ongoing dialog between artists and production people about what is right and wrong with a printed image. In many cases, the production department feels that “if only the artist had done it different – it would have printed better.” The artist’s comeback is – “I didn’t know that mattered.” Since many artists aren’t trained in screen printing, you can’t really blame them. In fact, when I work with large companies I encourage them to get artist’s on the production floor and let them see how that end of the business runs.
With that in mind, this article is written to help artists better understand the screen printing process and to be more responsible for the outcome of the final print.
- Take charge of the specifications.
This may be contrary to many shop’s thinking, but I personally feel that if you “built it” then you know what you had in mind. You should specify the print sequence, the mesh counts, the number of flashes, etc. (Figure 1) If you feel uncomfortable doing that, then the rest of this information should help. If nothing else, take time to work a few hours in the Screen Making, Ink and Production departments. - Get a production sample of every job. Learn from each job.
It always amazes me when artists tell me that they don’t see the final shirt. After I pick my self up off the floor from shock, I wonder “what the heck is wrong with that company? You can’t afford to give the guys who built the image a production sample to learn from?” - Determine the correct color sequence.
On a light colored shirt, we generally print light to dark, or smallest amount of ink to the most amount of ink. The reason for this is that inks pickup on the back of the screens and you don’t want dark colors contaminating lighter colors (figure 2).On dark shirts we generally print a base of white ink that is either a solid or halftone dots. This base must be flash cured and then colors are printed on top. A typical color sequence is light to dark BUT put any large ink area or dominant and important color last in the sequence (figure 3).For a real Process Color (CMYK) job, use the order of YMCK and put any spot colors after their like process color – red after magenta, etc. (Figure 4)
- Recommend the mesh selection.
This one will vary depending on the type of work you shop does. For general simple designs use a 45 (cm) mesh. For more complex, move up to 77. For more detailed jobs with lots of halftones use a 90 to a 120 mesh. For dark shirts you should use 77 to 90 for the underbase and 120 or higher for the tops colors. - No, this isn’t paper printing.
Forget most of what you learned in art school about paper printing. We take a great image and then just mess it up by converting it to large halftones (55 lpi to 65 lpi) and then put these dots on a screen mesh, and THEN we print these halftone dots on a knit shirt. Nothing will look the same.Even thought we do print some images with process color, most of our work is done with spot colors. On dark shirts we DON’T print CMYK process colors because they will become very dull when printed on an underbase. Instead we print dark shirts with standard spot color inks on a base of halftoned white ink. This is called “Fake” or “Simulate” process color. - What you see is not what you always get. (WYSINWYAG)
Yes, the image on the monitor looks great but that is NOT what you will get when it is screened. We already talked about how we mess up the image. Everything get’s FATTER when we screen print it. This is called “dot gain.” If you have a 20% density area in an image, chances are when you convert this to a 20% halftone dot and print it, the dot will grow up to 40%. You will now have almost a 30% dot on the shirt. This gets worse in the shadow areas. Your 70% dots might print as a solid. You must always think lighter when creating color separations to allow for all the dot gain (figure 5). - Cut the production guys some slack.
It is easy to sit in your art department and make minor tweaks after they show you the production sample. Give the production guys a break. A minor change of two or three colors means re-burning two or three screens, pulling the old screen off the press, setting up the new screens, getting them in registration, making a test print, etc., etc., etc. This is NOT easy.Matching colors is the same. It is very hard to match that little color chip printed on glossy paper with the color on a knit shirt (figure 6). Try to be flexible here. - Try to talk the same language.
I deal with artists every day and find that there is often two different languages. A production person might complain that the Red isn’t bright enough on the black shirt. You might wonder why the red isn’t brighter, when in fact the red has nothing to do with it. Red generally needs to be underbased on a black shirt and it could be that your underbase isn’t bright enough, OR, that the production people need to make the underbase brighter by slowing down the squeegee stroke, using a lower mesh count, changing the angle of the squeegee, or using a more opaque white. This will in turn make the red brighter! - Know your shop’s limitations.
There is no reason to expect your screen making department to hold a 2% dot on a screen. It is just not done. (OK, I know some of you can do it.) You need to do a test film with various densities from 5% and higher that your screen department can burn. Have them make a print and see what happens. Also, if your shop doesn’t use properly tensioned screens, you might get 50% to 60% dot gain or more. Allow for this when using halftone dots.If your shop can’t hold almost perfect registration, think about overlapping the black and colors from 2 to 4 points on spot color jobs. This is called a trap and has been covered in previous articles.
These are just some of the things you should think about when doing color separations for screen printing.
