What Is an Underbase in Screen Printing?
By The Velocity Wear Team
An underbase is a layer of white ink printed first, dried on press with a flash unit, then printed over with your design colours. On dark garments it stops the fabric colour showing through and absorbing the pigment, so a red stays red rather than sinking to maroon. It occupies its own screen, so it counts as a colour for setup purposes, and it changes both the cost and the feel of the finished print.
Why the Garment Colour Changes the Ink Colour
Screen printing inks are not fully opaque. A single pass of colour ink on a black garment lets the black influence what you see through and around the pigment, and the fabric also draws ink down into the fibres. The result is a colour that is darker, duller and less saturated than the swatch you approved.
Yellow suffers most, because it has the least tinting strength of any common colour. Print yellow directly onto navy and you get a murky olive. Print it onto a white base and it is yellow. That single comparison explains the whole technique.
The Flash Cure Step
You cannot print wet ink onto wet ink and expect a clean result, so the white base passes under a flash unit that gels the surface enough to accept the next layer. Only then do the colour screens come down.
This is why underbased jobs run more slowly. Every garment goes through additional stations and a heat step, the press cycles slower, and the operator has to keep the flash consistent. Slower run time is part of what you are paying for, alongside the extra screen.
Choke and Trap: The Detail Nobody Mentions
If the white base were printed at exactly the same size as the artwork, any tiny misalignment between screens would show a white halo peeking out from behind the colour. So the base is deliberately printed slightly smaller than the design, a technique called choking, so the colour layer overlaps its edges and covers it.
This has a practical consequence for your artwork. Very fine lines and small text can end up with almost no base under them once choked, which makes them look duller than the rest of the print. If your design has a strapline in thin type sitting alongside bold shapes, expect the thin type to read slightly softer, and consider whether it needs to be bolder.
What It Does to Hand Feel
Every layer adds thickness. An underbased print is white ink plus colour ink plus, on some designs, a highlight white on top, and you can feel that stack with your fingers. Across a small chest logo it is unremarkable. Across a large solid back print it becomes a noticeably firm panel that does not move with the fabric.
There are ways to reduce it. A lighter base deposit, a finer mesh, and designs that break up solid areas all help. But the physics do not change: opaque colour on a dark garment means more ink on the shirt, and more ink means more hand. If a genuinely soft print on black is the priority, the honest answer may be a different method or a lighter garment.
When You Can Skip It Entirely
- Light garments, where the fabric is not competing with the ink and colours print true in one pass.
- Single-colour white or very light ink on dark fabric, which is effectively acting as its own base already.
- Deliberately faded, vintage or distressed looks, where the garment showing through is exactly the point.
- Tonal prints, where the ink sits close to the garment colour and a subtle shift is the intended effect.
- Designs printed in a heavy, high-opacity ink chosen specifically to cover in a single hit on dark fabric.
What It Costs You
The base needs its own screen, its own emulsion and exposure, and its own registration on press, so it is charged as a colour. A design you think of as two colours on black is three screens in practice, and the white is doing real work.
That is worth knowing before you choose a garment colour. Moving a design from black to a light heather can drop a screen from the job and speed the run, and on a tight budget at moderate quantity that decision can matter more than the design itself.
“"White ink is the most expensive colour in the job, and it is the one nobody sees."”
The Alternatives on Dark Garments
Digital methods solve the same problem differently. DTF prints a white backing layer as part of the transfer, so opacity on dark fabric is built in with no extra screen or setup. DTG applies a pretreatment and prints its own white base, the same principle executed by a machine rather than a press operator, and it stays cotton only.
For short runs of detailed or full-colour work on dark garments, that automation is usually the better answer. For bold designs at volume, screen printing with a proper underbase still gives the most opaque, hardest-wearing result, which is why it remains the standard for large runs.
What to Look For in a Proof
When you review artwork for a dark garment, check two things. Whether the colours in the proof are shown as they will appear over white rather than over the garment. And whether any element is thin enough that choking will leave it under-based.
Lay the design out in the Design Studio on the actual garment colour before approving. Seeing the artwork against navy rather than against a white background settles a surprising number of arguments before production starts, and production only begins once artwork is approved.