Printed on the surface
Screen printing pushes thick opaque ink through a fine mesh stencil, one screen and one colour at a time. Each colour in your design needs its own screen, so the method rewards a small palette of flat, solid colours and is unsuited to photographs and smooth blends. What it gives back is unmatched: the ink sits thick and dense on the fabric, the colour is more saturated than any digital method can reach, and the print lasts for years.
Before anything is printed, your artwork is separated: each distinct colour is isolated onto its own screen, and the screens are printed in sequence with the garment held in registration between passes. That is why the number of colours, not the amount of detail, is the thing that shapes a screen-printed design.
A design of two or three flat colours is the natural fit. Up to 6 separations are practical; past that, registration between screens gets harder and every additional pass adds a place for a hairline misalignment to show.
There is no way to print a smooth gradient with a single screen — the ink is opaque and lays down at one density. Blends are simulated instead with halftones: dots of one solid colour at varying size, which the eye reads as a lighter or darker tone.
A photograph can be screen printed by separating it into halftone screens, but it is specialist work and the result is stylised rather than photographic. If a design depends on a photograph reproducing faithfully, direct-to-garment or direct-to-film printing is the better route.
Ink spreads a little as it is pushed through the mesh, so the thinnest lines close up and the smallest gaps fill in. Keep strokes solid and give small counters — the enclosed spaces inside letters like a and e — a little more room than you would for a digital print.
Where two colours meet, tiny registration shifts between passes can leave a hairline of garment showing. Overlapping the shapes very slightly, rather than butting them exactly edge to edge, makes the join forgiving.