Pinning.

A short, deliberately incomplete UV exposure given to ink just after it is jetted, gelling the drop before it can finish spreading. A UV drop keeps wetting out on the substrate until something stops it, so the size of the printed dot is decided by how long it stays liquid; a low-power pinning lamp closes that window and holds the dot near the size the RIP intended, which is what keeps fine detail sharp instead of gaining. The same step sets a white underbase so the colors jetted over it sit on top rather than sinking in, and it is not a cure: pinned ink still has to pass the main lamp, and treating a pinning pass as finished leaves soft ink under a surface that looks done. Pinning sources lose output as they age, so an under-pinned run gains dot quietly across a shift, and small type goes unreadable on work already boxed, which is a reprint of the whole run.