UV inkjet and white-ink underprint

UV inkjet jets ink that is cured instantly by UV light, sitting on the surface rather than soaking in, so it works on nearly any substrate — paper, film, foil, clear — and is fast-drying, low-VOC, scuff-resistant, and vivid. White underprint is the enabling trick on clear or dark stock: a high-opacity white is laid down first, then CMYK on top, so the substrate does not show through and colors stay saturated — essentially an opaque canvas. White can also overprint as a protective or special-effect layer, and multiple passes can build a raised 3D feel. It is what lets clear BOPP/PET labels show saturated color.