printseps.com / guides / spot-color-vs-simulated-process

Spot color vs simulated process: choosing the right separation

PrintSeps guides · updated September 2026

Every multi-color screen print job starts with the same decision: which kind of color separation does this artwork need? For the vast majority of jobs the answer is one of two — spot color or simulated process. Choosing right determines your screen count, your ink room's afternoon, and whether the print looks crisp or muddy.

Spot color separations

A spot color separation splits artwork into a small number of solid, flat ink colors — one plate (and one screen) per ink. A three-color logo becomes three plates: say, black, red, and gold, each printed with an ink mixed to match (usually to a Pantone solid).

Use spot color when the art is made of defined shapes and flat fills: logos, lettering, mascots, most vector art. Its strengths:

• Exact color — ink is mixed to the target, so brand colors match every run.
• Opacity and punch — solid plastisol lays down clean, saturated color, even on dark garments over an underbase.
• Simple press setup — fewer screens, simpler registration, easier reprints.

Spot separations can still carry halftones — a shaded area of the logo can print as a dot gradient of the same ink rather than a separate color. That keeps the screen count down while adding depth.

Simulated process separations

Simulated process (often just "sim process") rebuilds photorealistic or painterly artwork from halftone dots of a handful of standard opaque inks — typically 4 to 8 plates, plus an underbase white on dark shirts. Unlike true CMYK process printing, sim process uses ordinary opaque inks (a red, a gold, a royal, a black…), which is why it works on black garments where transparent CMYK inks fail.

Use sim process for photographs, airbrush-style illustration, detailed skin tones, fire, chrome, fur — anything with continuous tone. Done well, from a few feet away the print reads as full color; up close it's an interlocking mesh of halftone rosettes.

The hard part is the separation itself: deciding how eight inks share the work of a million-color image, how much underbase shows through, where to choke the base so dark inks stay rich, and what halftone angles keep the dots from moiréing against the mesh. This is the step that traditionally took an experienced separator hours in Photoshop channels — and it's exactly the step automated tools now do in minutes.

How to choose, quickly

Common questions

What about index separations?

Index separations use square, randomly-dithered pixels instead of halftone dots. They're forgiving on press (no moiré) but need more colors for smooth tone and can look coarse. Sim process has largely displaced index for photorealistic work, but index still has fans for grunge and texture-heavy art.

Does sim process need special inks?

No — that's the point. It uses the standard opaque plastisols already on your shelf. True CMYK process needs transparent process inks and behaves very differently on dark garments.

What LPI should sim process halftones use?

Most shops run 45–65 LPI depending on mesh counts and press registration. 55 LPI on 230–305 mesh is a common starting point; coarser if your exposure unit or registration struggles.