Why thin lines and small text fade on dark shirts (DTF white underbase choke)

The design looked crisp on screen. On a white shirt it prints fine. But on black, the thin outline is dull and patchy, the script font has faded, and the tiny text underneath has almost vanished.

Nothing is wrong with the ink. It's how DTF prints on dark fabric, and it's predictable, so you can check for it before you print.

The white underbase, and why it shrinks

On a dark shirt, every colour in a DTF transfer sits on a layer of white ink, the underbase. Without it, colours would sink into the fabric and look muddy. (For the bigger picture, including knockouts that let the shirt colour show through, see designing for dark shirts.)

The printer's software doesn't print the white exactly the same size as the colour. It pulls it in slightly from every edge. That's the choke (sometimes called shrink or white spread). It's there so the white never peeks out as a thin white line around the design if the layers are a fraction out of line.

On a bold shape you never notice: the white is a hair smaller than the colour, and the colour covers it. On a thin line, it's a different story.

How thin is too thin

The choke eats in from both sides of a line. So:

• A line narrower than twice the choke has no white under it at all. The colour lands straight on the dark fabric and looks faded, or disappears.
• A line only a little wider keeps a sliver of white, which tends to break up and look patchy.

Most DTF software uses a choke of 1–2 pixels at 300 DPI:

• 1 px choke (0.08 mm): no white below 0.17 mm; safe from about 0.37 mm.
• 2 px choke (0.17 mm): no white below 0.34 mm; safe from about 0.54 mm.
• 3 px choke (0.25 mm): no white below 0.51 mm; safe from about 0.71 mm.

At 300 DPI, 0.54 mm is about 6 pixels. The usual suspects are fine script fonts, thin outlines and keylines, hatching and line art, small text in a light weight, and the fine texture of a distressed design.

Print size changes everything

Lines shrink with the print. A 3-pixel outline in a 3,600-pixel-wide file is 0.25 mm wide printed at 12″, and just 0.08 mm on a 4″ left-chest logo. The same design can be fine on a full front and fail as a pocket print, so always check at the size you'll actually print.

How to fix it

• Thicken the thin parts. Grow only the lines that are too thin, just enough to keep their white. Bold areas don't need to change.
• Print it bigger. If it's a small logo, a slightly larger print may be enough.
• Lower the choke, carefully. A smaller choke keeps white under thinner lines, but makes a white edge more likely to show if the layers shift. For one design with fine details, changing the file is usually safer.
• Remove loose specks. Tiny bits of ink under about 0.5 mm hold too little adhesive and peel off in the wash anyway.
• Have it redrawn. Script and line art can be rebuilt slightly bolder while keeping the look. That's part of our print-ready design service.

Check any design for free

Our free DTF white ink checker shows you exactly where this will happen:

1. Drop in your PNG and choose the width you'll print.
2. Set your printer's choke, or leave it on Typical.
3. Problems are marked on the preview: red where there's no white at all, amber where the white is too thin, and purple for loose specks. Zoom in, or step through them one by one.
4. Click Fix my file to thicken the thin lines and remove the specks, compare, and download the fixed PNG.

Free, no account, and nothing is uploaded.

Questions

Does this happen on white shirts?

Much less. On a white or light shirt a thin line with no white under it still shows, because the fabric behind it is light. It's dark and coloured shirts where the colour needs white under it.

What's a normal choke setting?

Most DTF printers use 1–2 pixels at 300 DPI, about 0.1–0.2 mm. You'll find it in your RIP's white ink settings, often called choke, shrink or white spread.

Will thickening change my design?

Only the parts that are too thin, and only by as much as they need. Fine script gets slightly bolder; everything else stays exactly as it was. Always compare before you print.

Why does the checker flag my small text but not the big text?

Because the strokes in small text are thinner. The same font that's fine at 2″ tall can be too thin at half an inch.

Is this the same as the white box or haze problem?

No. A white box or haze is white ink printing where it shouldn't, under hidden pixels. This is the opposite: white ink missing where it should be, under thin lines.