An underbase is essentially a layer of white ink covering the full area of a design, which is printed before any of the other colors. Printing this white layer ensures that colors stay true and maintain opacity when printing colors on dark garments.

Screen Printing inks aren’t very opaque, in a sense that they are quite thin. This is so colors can blend & mix when printed and so it can be printed through finer mesh screens for better detail hand softer ‘hand’ or ‘feel’. In most cases when printing on dark colored fabric with plastisol inks, a white underbase layer first needs to be printed as an “undercoat” before printing the colored inks. This ensures the print is vibrant on dark garments. It is somewhat like a primer when painting a wall in your house; the primer seals and smooths the surface and presents a good surface to paint onto.

This image shows how the colors would look printed without an underbase screen, directly onto the black garment. The darker image shown reflects the print with an underbase. See how much brighter the third one is? That’s all thanks to the mighty unsung hero of screen printing – the underbase.

Printing an under base is necessary when the ink color is lighter than the garment color. This applies to most garment colors with the exception of white & light / pastel colors. We’ll be able to advise you on this during the quoting process. 

The short answer is yes. The visible white areas of your design still need 2 coats. Some print shops might cut corners by printing the whole area of the image white twice, and then stacking the colors on top. The issue with this is that while the white portions of the image are nice and bright with 2 coats, the rest of the image will have a third coat of ink on top, meaning the print is unnecessarily thick and more likely to crack and wear out in the wash. Thick ink deposits can also end up looking super tacky and shiny as well, especially if using plastisol inks.

For example – say you have a design that contains red, blue, green and white and you want it printed on a black t-shirt. 

The correct way to print this design would be to print the whole image in white ink once, flash dry it (this is the underbase), then print the remaining visible colors (red, blue, green and white) on top. This makes for a nice even, super high-quality print that will not only look great out of the box, but it’ll stay looking that way too.

Feel free to download this image to save for future reference if needed. Send us your graphic and our art department will review it and provide feedback.