Simulated process, often shortened to sim process, takes a photo or painted artwork and breaks it into a handful of spot colors chosen for that particular image, typically a white underbase plus several colors and a highlight white. Halftone dots in each screen blend on the shirt into what reads as continuous color.
Because the inks are opaque and picked per design, sim process works on black and colored garments where four-color process struggles. It suits detailed band art, illustrations and photo-real designs. It depends on skilled separations and careful press setup, and it usually needs more screens than a simple logo, which shows up in setup cost.
If your design is full color, ask whether the printer plans sim process, CMYK or DTG, how many screens the separation uses, and whether you can approve a strike-off before the run. The separation methods guide explains when each approach fits.