Here is a great article that I recently found: Enjoy!
“What Every Artist Should Know About Screen Printing
Scott provides artists with a crash course in effective communication with the production department.
There is often an ongoing dialogue 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, “1 didnt know that mattered”. Since many artists aren’t trained in screen printing, you can’t really blame them. In fact, when 1 work with large companies 1 encourage them to get artists on the production floor and let them see how this 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.
1. Take charge of the specifications
This may be contrary to many shops’ thinking, but 1 personally feel that if you ‘built it’ then you know what you had in mind. Artists should specify the print sequence, the mesh counts, the number of flashes and so on (figure l). 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 andproduction departments.
|Job detail to be attached to each film|
|Customer||Job No.||Ink Colour|
|Garment Colour||Print Location||MeshCount|
|Figure 1. Mark the films with recommended mesh selection, colour sequence and more|
2. Get a production sample of every joh and learn from it
It always amazes me when artists tell me that they don’t see the final shirt. After I pick myself up off the floor from shock, 1 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?
3. Determine the correct colour sequence
Figure 2. On light shirts, print light to dark ink, or the smallest area of coverage to largest.
On a light coloured shirt, we generally print light to dark, or smallest amount of ink to most amount of ink. The reason for this is that the inks pick up on the back of the screens and you don;t want dark colours contaminating light colours.
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 colours are printed on top. A typical colour sequence is light to dark, but put any large ink area of dominant colour last.(see Figure 3.)
Figure 3. On dark shirts, print a base of white ink and then the lightest colour to the darkest colour with the largest coverage areas or most dominant colour last (if possible).
For a real Process Colour (CMYK) job, use the order of YMCK and put any spot colours after their like process colour – red after magenta and so on (see figure 4).
Figure 4. CM YK Process Colour is printed in the order of YMCK, with spot colours printed affer a similar process colour – red after magenta, and so on.
4. Recommend the mesh selection
This one will vary depending on the type of work you shop does. For general, simple designs use a 45T (threads per cm) mesh. For more complex work, move up to 77T. For even more detailed jobs, with lots of halftones, use a 90 to a 120T. For dark shirts you should use 77T to 9oT for the underbase and 120T or higher for the top colours.
5. 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 though we do print some images with process colour, most of our work is done with spot colours. On dark shirts we don’t print CMYK process colours because they will become very dull when printed on an underbase. Instead we print dark shirts with standard spot colour inks on a base of halftoned white ink. This is called ‘Fake’ or’Simulated’ process colour.
6. What you sec 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 gets ‘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 by up to 40% of its original size. 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 (100%). You must always think lighter when creating colour separations to allow for the large amount of dot gain (see figure 5).
Figure 5. What you sec on the monitor will just look worse when printed because of dol gain, as illustraled above.
7. Cut tbc production guys sorne 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 colours means reburning two or three screens, pulling the old screen off the press, setting up the new screens, getting them in registration, making a test print and so on and so on. This is not easy.
Matching colours is the same. It is very hard to match that little colour chip printed on glossy paper with the colour on a knit shirt (figure 6). Try to be as flexible as possible, here.
Figure 6. Be flexible when trying to match colours. lf you have picky customers, you need to try to educate them to the limitations of the process
8. Talk tbc sarne 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 slow- ing 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!
9. Know your shop’s limitations
There is no reason to expect your screenmaking department to hold a 2% dot on a screen. It is just not done. (OK, OK, 1 know some of you can do it!) You need to do a test film with various densities frorn 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 colours from 2 to 4 points on spot colour jobs. This is called a trap and has been covered in previous articles.
These are just some of the things that any artist should consider when creating colour separations for screen printing. .”