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What is Underbase? - Printing on Dark Shirts

So you want to print your custom design on a dark shirt. Chances are we’ll have to lay down a layer of underbase to the shirt before we can fully print the artwork on your tee. Think of the underbase as the true canvas to present your work on. It’s actually a pretty simple process, but why is it so necessary?

Dark fabrics are an interesting beast when it comes to the screen printing business, but it’s a very common thing. A “dark” shirt is basically any colored shirt that isn’t white or pastel, so we run into it all the time.

In screen printing, plastisol ink doesn’t normally have the opacity to present well on dark clothing, so we print a white ink underbase onto the shirt before applying any other colors to it. The underbase acts as a foundation for the ink as well as a primer that really makes your design pop by preventing the fabric from soaking up all the ink. The result is a very vibrant and beautiful print.

Print Without Underbase   Print With Underbase

Preparing the Artwork

If we base the underbase on an unaltered version of your artwork, there’s a chance that the white ink underbase could “bleed” out and show up under the actual printed art, ruining that design you worked so hard on.

In order to prevent the white underbase from showing up in the final print, the underbase has to be formed by “choking” the design. Don’t worry, your art is safe. It’s not as gruesome as it sounds. “Choking” simply refers to slightly decreasing the outline of the artwork to use as an underbase. You can see an example of a square being choked below. The light blue is the original artwork, with the dark blue showing the choked version.

Applying the Underbase

After the artwork has been choked, we convert it to a screen that we use to apply a layer of white ink. That’s the underbase that we’ve made such a fuss about. We flash cure the underbase, which means briefly exposing it to a flash dyer that will “gel,” or partially cure the ink. This prepares the underbase to accept the rest of colors of your design, which we apply layer by layer. It’s standard screen printing fare from there.


Once we’re done, one shouldn’t notice there’s an underbase at all. But you’ll know better, having read this. You’ll know presence of an underbase due to the fact that you can actually see the print on a dark shirt in the first place!

When Not to Use an Underbase

There may be times at which you don’t want to apply an underbase to your printed tee. On such occasions, you’re either printing on a white or light-colored shirt, or you’ve got a desire for that “vintage” look. Having your print look a little faded can actually be rather stylish in some cases. That’s totally a cool and legitimate aesthetic, and we’re open to doing whatever you want so you can create the most fashionable shirt of your dreams.

Talk To A T-Shirt Design Specialist!