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How to Print the Ultimate Underbase

(February/March 2018) posted on Mon Mar 12, 2018

Though white is traditional, using other colors for your underbases can help you create incredible designs on dark garments.

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By Thomas Trimingham

Remember that when you create separations using an alternative underbase, you will need to pull a slightly more saturated color for the accent or top-printed colors because the underbase will change them, making them slightly duller and/or changing their hue. As with most color mixing, avoid using a color for an underbase that might blend with an overprint color to create an unwanted end result (such as a light green underbase and a magenta overprint, which would combine to create a gross brown).

Be careful promising this process to a client in the art approval stage if you haven’t tested the color combinations first. You may have to make some on-press changes the first few times you attempt an alternate color underbase. You don’t want to have to revise your separations multiple times on a rush job for a picky customer.

Another time you may need to use an alternate underbase involves art with image elements that fade off into a dark shirt. Imagine a brick wall that slowly fades into the shadows on a black shirt. With such a design, it might be advantageous to use a mauve or slightly reddish-gray underbase because it will make for a more subtle, less heavy print. It also prevents the white underbase showing through as it fades out into the shirt background.

Some printers design this type of artwork so that one or more of the overprint colors print off the underbase and directly onto the shirt in parts of the image. This is an advanced technique and it’s vitally important to test, especially with shirt colors other than black. I’ve gone so far as to get samples of such shirts and then test print the underbase and overprint colors for the job, reducing the opacity of the underbase in stages so I could see what different combinations might yield rather than just guess. For a high-volume job, the extra effort can pay off. Even black shirts can vary from one manufacturer to another, with dyes that can skew toward another color like magenta or blue and that might produce a different hue than you expect.

Another common challenge where this technique can help is grunge artwork that has a lot of tiny splatters or distressed pieces, like the shirt in Figure 8 (above). This type of design can cause some real headaches with registration and/or screen stretch on press between the underbase screen and the overprinted colors. Here, using an alternate underbase color can save a lot of profit. Those tiny image elements will be similar in color to the underbase, eliminating the registration concerns and allowing setup to go much faster. The main concern is if the colors from the original design that you’ll be overprinting are too bright for this to work.

A final challenge that an alternate underbase can make easier involves full-color designs that are intended to have a washed-out look, such as the one in Figure 9 (below). Imagine a vintage wine label with a lot of colors. You want to print it on a tan shirt, but the artwork has a dull look to it as though it has been in storage for years. This would be a good situation to use an off-white underbase to help dull the top colors, making the print softer. It would also make the entire production process simpler because you could use regular, semitransparent colors and just let the underbase and shirt create the washed-out look. You may have to test it to get the right underbase color, but it would be a lot easier then custom mixing all of your top colors and printing them on a white underbase.

Printing an underbase with a color other than white can be an effective and useful way to cut the number of colors in a job, reduce setup time, and prevent press headaches. You just need the right design combined with some experience. Take the time to test variations of the press setup, inks, and separation methods so you can plan and anticipate the results you might get the next time you’re presented with a duotone or grunge design. With enough practice, this process can be a valuable solution that will provide great prints that are softer and more easily color matched to the original artwork.

Read more from Screen Printing's February/March 2018 Garment Issue or explore more prepress and art department advice from Thomas Trimingham.


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