Why a halftone disappears into dark fabric
A halftone dot does not print a lighter shade of ink. It prints full-strength ink in a small dot and nothing at all in the gap around it, and your eye blends the two into a tint at reading distance. That blend depends entirely on what the gap shows. On a white shirt, the gap shows white, so a 30% red halftone reads as a light pink, close to what you designed. On a black shirt, the same gap shows black, so that light pink becomes a dark, desaturated smear — the ink is identical, but the substrate it is blending against is not.
A white underbase is a layer of opaque white printed first, under everything else, purely to give every colour above it a neutral, light surface to blend against instead of the garment. It is not a colour in the design; it is the substrate the rest of the design is built to expect.
Choke the underbase, never spread it
Registration on a garment press will never be perfect, so plan for it to drift a little. The standard fix is to make the white underbase shape one or two points smaller than the colour printed over it — a "choke." If registration shifts slightly, a sliver of dark fabric peeks out at the edge instead of a sliver of white. A thin dark line disappears into a dark shirt; a thin white line around your entire design looks like a mistake.
This is the same honest limitation already covered in the lino and block printing guide: the tool does not spread or choke shapes automatically. Build the choke into the artwork itself, before you separate — inset the white shape by a point or two in your design software, the same way you would plan a deliberate overlap for a lino block.
One mesh for coverage, maybe another for detail
A solid underbase needs to lay down enough opaque white to fully block the garment colour, which wants a coarser mesh and a heavier ink deposit — commonly 110–160 mesh for a plain white base. If the colours going on top of it carry fine halftone detail, a coarse underbase can print through with a slightly rough, textured surface, so printers commonly move the underbase itself up to 180–200 mesh for a smoother base when detail is going on top of it.
| Layer | Typical mesh | Why |
|---|---|---|
| Solid white underbase, bold colours on top | 110–160 | More ink deposit, better opacity over dark fabric |
| White underbase under fine halftone detail | 180–200 | Smoother surface for the detail to sit on cleanly |
| Halftone (soft-hand) underbase | 110–156 | Coarse mesh at a high dot percentage, see below |
These are separate from the mesh a top colour needs for its own detail — see the mesh count to LPI chart for the smallest dot each mesh can hold.
Why that usually means two exports, not one
Worth knowing before you separate: mesh and the halftone-or-solid raster setting are both job-wide settings in the tool right now, not adjustable per ink within one export. If your underbase genuinely needs a different mesh, or a fully solid fill while your top colours stay halftoned, run the separation twice — once for the underbase ink on its own, at its own mesh and raster setting, and once for the top colours at theirs. Line the two exports up using the registration marks the tool already prints in the margin of every film.
If you would rather stay in one pass, keep the underbase in the halftone screening you are already using for everything else, just at a high dot percentage — 90–100% coverage reads as visually solid at normal viewing distance, and you get the whole job, underbase included, out of a single export.
Flash it, do not cure it
Between the underbase and the first colour on top, the underbase needs to be flashed: heated just enough to gel the ink so the next colour does not mix wet-into-wet, not heated long enough to fully cure it. Plastisol typically gels somewhere around 240–250°F, but check your own ink's data sheet since it varies by brand. A properly flashed underbase feels slightly tacky to a light touch but should not smudge. Flash it too long and it fully cures, which seals the surface and stops the next colour from bonding to it properly — the opposite problem, and a harder one to notice until the print fails in the wash.
The soft-hand alternative: a halftone underbase
A fully solid underbase lays down the most ink, which is also the stiffest, heaviest print on the garment. Printing the underbase itself as a coarse, high-percentage halftone — commonly 60–70% dot coverage through a coarse mesh — deposits noticeably less ink. Colours on top read very slightly less bright than over a fully solid base, but the print sits softer and lighter on the fabric, which is the usual trade printers make for anything meant to feel like a soft, worn-in shirt rather than a poster on fabric.
Separating a dark-garment job?
Add white as its own ink, set the mesh and raster for that export, then repeat for your top colours if they need different settings. Free while in beta.
A short checklist
Get right before you print
- Underbase choked 1–2pt smaller than the colours on top
- Coarser mesh for a solid base, finer if detail sits on top of it
- Flash to a gel, checked by touch, not fully cured
- Two exports if underbase and top colours need different mesh or raster settings
Common mistakes
- Underbase the same size as the top colour, or bigger
- One mesh setting used for both the base and fine detail on top of it
- Flashing until the underbase feels completely dry and smooth
- Designing a tint as if it will sit on light fabric when it is going over white
Common questions
Why does my halftone look muddy on a black shirt?
Because the gaps between halftone dots show the garment colour, not white. On black fabric that darkens and desaturates any tint unless a white underbase sits underneath it first.
Should the underbase be bigger or smaller than the top colour?
Smaller — choke it by one or two points. If registration drifts slightly, a sliver of dark fabric at the edge is far less visible than a sliver of white peeking out from behind the design.
What mesh should I use for a white underbase?
110–160 mesh for a solid, fully opaque base. If fine halftone detail is printing on top of it, move the underbase itself up to 180–200 mesh for a smoother surface.
Can I print a solid underbase and halftoned colours in one export?
Not with different mesh or raster settings, since both are job-wide settings in the tool right now. Either run two exports, one per setting, or keep the underbase halftoned at a high dot percentage so it reads as solid without needing a second pass.
Do I need to fully cure the underbase before printing the next colour?
No, and you should not. Flash it just enough to gel, typically a light touch that feels tacky but does not smudge. A fully cured underbase seals the surface and the next colour will not bond to it properly.
What is a halftone or highlight underbase?
Printing the white base itself as a coarse, high-percentage halftone (roughly 60–70% coverage) instead of a solid fill. It deposits less ink for a softer hand feel, at the cost of colours reading very slightly less bright than over a fully solid base.
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