UV-fluorescent Hi-lites
Small coloured or colourless particles embedded in the paper during the manufacturing process. The particles glow when exposed to UV light (fig. 1).
a
b
c
Fig. 1. UV-fluorescent hi-lites. 5 000 Costa Rican Colones (2005):
a – Hi-lites glowing under UV light; b – zoomed image under white light; c – zoomed image under UV light