#Overview
In screen printing, everything starts with the film positive: the transparent film you lay over your screen once it's coated with photosensitive emulsion, before exposure. Where the film is opaque, the emulsion doesn't cure — it washes out in the rinse — and ink will pass through. Where the film is transparent, the emulsion cures and blocks ink.
Direct consequence, and it's THE trap for beginners coming from alternative photographic processes: the film positive is a positive, not a negative. A dark image on the film gives an inked area on the fabric or paper. Calibration Flow handles both polarities — for screen printing, you work in Positive mode (Type tab).
#Producing the film positive, step by step
- Import your image — photo, illustration, logo. Local file or library.
- Type tab → Positive. This is the polarity screen printing needs; the preview regenerates.
- Turn on halftoning (Dither option → Auto). A screen printing screen can't lay down "40% ink" on a single dot: it either lets ink through or it doesn't. Tones need to become dots of varying size — that's halftoning. Calibration Flow applies a classic AM halftone, rotated screen, with automatic fallback to error diffusion when the setup doesn't suit it well. Details and fineness choices: Halftone, lpi and mesh count.
- Choose format and resolution — A4 or A3+, 300 to 500 dpi. Screen fineness follows resolution.
- Download the PNG and print it on inkjet transparency, pigment inks, with color management off, maximum density. The black on the film needs to genuinely block UV — the same requirement as for an alternative-process negative, and the same print settings apply.
#Multiple colors: the separations
Two or three flat (spot) inks. This is the most common regime in craft screen printing — and it's exactly what Sanguine does: it splits your image's tonal range into 2 or 3 film positives, one per ink, printed in register. Each film carries its label, its exposure rank and its bounds, and an internal check verifies the stack rebuilds the image before generating anything. The sharing slider sets your tolerance for registration.
CMYK four-color. Calibration Flow also separates into 4 films — Cyan, Magenta, Yellow, Black (and up to 7 inks in Full Gamut). Two honest caveats for screen printing: all films share the same screen angle — in halftoned CMYK, that can produce moiré between colors, whereas traditional screen printing prepress rotates each film's angle; and screen printing inks aren't offset inks — run a test before a series. For 2-3 color work, Sanguine sidesteps the problem by construction: each ink carries a different tonal slice, not the same screen stacked on itself.
Registration. Turn on registration marks: small Venn-diagram-style patterns rather than crosses — a half-millimeter shift is immediately visible on overlap.
#What calibration changes in screen printing
A silk screen isn't neutral: between exposure (the film's small dots don't always cure cleanly) and printing (ink spreads through the mesh), midtones darken and highlights disappear. That's dot gain, and it depends on YOUR combination of mesh, emulsion, ink and squeegee pressure.
Calibration Flow's answer is the same as for every process it calibrates: you print a 25-patch target, pull it through screen printing, photograph the result, and the app measures what each value actually became and builds the compensation curve — applied automatically to all your subsequent film positives. Details: Calibrating dot gain.
That's the difference from ordinary separation software: they separate, Calibration Flow measures your shop and corrects accordingly.
#Key takeaways
| Element | Value |
|---|---|
| Polarity | Positive (a screen printing film positive is not a negative) |
| Halftoning | AM halftone, error-diffusion fallback — Dither option |
| Formats | A4, A3+ · 300 to 500 dpi |
| Separations | Sanguine 2-3 inks (spot) · CMYK 4 films · Full Gamut up to 7 |
| Registration | Mini-Venn marks |
| Calibration | Measured 25-patch target → dot gain compensation curve |
| Access | Free (5+ ink HD export requires Pro Mode) |
#FAQ
Q: Positive or negative for a screen printing screen? A: Positive. The photosensitive emulsion cures where light passes through; the film must be opaque wherever you want ink. Positive mode, in the Type tab.
Q: Can I print the film positive on a laser printer? A: Pigment inkjet gives better UV density on transparency. A laser can be enough for solid flats; for fine halftoning, inkjet is safer. Either way: test-expose first.
Q: Does this work for both textile AND paper? A: The film positive is the same. What changes is your screen's mesh count, and so the reasonable halftone fineness — see Halftone, lpi and mesh count.