Separation Checklist

Get the final width, garment color and ink count signed off first. Changing size after seps means redoing halftones and traps.

Halftones and line weights only make sense at final size.

Free programs: GIMP: check size and resolution under Image → Print Size (X and Y resolution set the printed size) [12].

Anything thinner than your screen can hold will close up or wash out. If you’re working from a raster logo, trace it to clean shapes first.

Free programs: Inkscape: Path ⇒ Trace Bitmap (Shift+Alt+B) turns a raster image into paths [8]. Or try the site’s Auto Trace.

It makes each plate easy to build and check.

Free programs: Inkscape: select one shape, then Edit ⇒ Select Same ⇒ Fill Color to grab every shape with that exact fill [6].

Label each plate with the ink it prints (“White underbase”, “Red”, “Black”) so nobody burns the wrong screen.

Every ink color needs its own solid black positive.

CorelDRAW: File → Print, Color tab, enable Separations (called Print separations in older versions). On the Separations tab, check only the plates you want [1][2].

Free programs: Put each ink color on its own layer, fill that layer solid black, and export or print one layer at a time. GIMP: Colors → Threshold turns a grayscale channel or layer into pure black and white [10]. Image → Mode → Indexed can reduce raster art to a set number of colors (Maximum number of colors, Remove unused colors from final palette) [11].

If a spot color gets converted to process, it ends up spread across CMYK plates instead of its own screen.

CorelDRAW: The Convert spot colors to box on the Color tab changes spot colors to process at print time. Leave it off for spot-color work [1].

A stray object in the wrong color makes an extra screen. Count plates against the ink list.

Screens and monitors lie. Mix the ink to a printed swatch, a garment sample or a drawdown the customer approved, and note the formula.

Without it, colors sink into the shirt and look dull.

Shrink the underbase slightly inside the top colors so a little misregistration doesn’t show a white edge.

Free programs: Inkscape: Inset (Ctrl+( ) shrinks a path, Outset (Ctrl+) ) grows it. Dynamic Offset (Ctrl+J) gives a draggable offset you can fine-tune [7].

Open areas meant to be the garment color should have no underbase at all.

Free programs: Inkscape boolean Difference cuts one selected shape out of another; it works on two objects at a time [7].

It usually prints last, over the colors, so it needs a separate screen from the underbase.

Too fine a line count for the mesh and dots fall through or close up. Check the Mesh & LPI Chart.

CorelDRAW: File → Print, Color tab, enable separations, then Separations tab and click Advanced (in older versions, enable Use advanced settings first). Screen frequency, screen angle and halftone type can be set for spot colors as well as process colors [1][2].

Same-angle screens stacked on top of each other are a common cause of moiré. CorelDRAW’s own example sets one spot color at 45° and another at 90° [1].

Round, elliptical and line dots print differently on press. Print a test strip before you commit a big job.

CorelDRAW: Halftone type in the Advanced separation settings [1].

Free programs: GIMP: Filters → Distorts → Newsprint offers Line, Circle, Diamond, PSSquare (Euclidean) dot and Crossing Lines patterns, with Period (in pixels) and Angle. GIMP’s docs say the filter simulates halftones rather than making print screens, so test it; if you print the result, set anti-alias oversampling to 1 (off) [9]. Krita: the Halftone filter (Artistic filters) builds the screen from fill-layer generators and has Hardness and Invert options [13].

Tiny highlight dots that won’t hold on the screen and shadow dots that fill in both need a fix in the art before output.

A small overlap hides the gap that appears when screens are slightly off. Spread the lighter color under the darker one.

CorelDRAW: Select an object, then Object and choose Overprint fill, Overprint outline or Overprint bitmap (also on the right-click menu). Automatic options: always overprint black (objects with 95% black or more by default) and auto-spreading [3].

Free programs: Inkscape: Outset or Dynamic Offset grows a shape for a spread; the Stroke to Path command turns a stroke into a filled shape you can use as a trap [7].

Make sure only the colors you meant to overprint do.

CorelDRAW: In the print dialog, the Document overprints list offers Ignore (knock out) or Preserve [3].

Matching marks let you line up screens on press fast.

CorelDRAW: File → Print, Prepress tab, enable Print registration marks and pick a style. The paper must be 0.5 in larger than the page on all sides [4].

Free programs: Draw one mark, copy it to every layer at the exact same position, and keep it outside the print area.

Job name and ink color on every film saves mix-ups in the screen room.

CorelDRAW: Prepress tab, Print file information adds a job name to each sheet [4].

Screen printing films are positives: ink areas black, everything else clear.

CorelDRAW: Prepress tab, Paper/film settings: leave Invert off (that makes a negative). Mirror sets emulsion-down and prints backward [5].

Thin or speckled black lets light through and gives you pinholes and soft edges. See the Film Printer tool.

Stack them on their registration marks before you burn any screens.