Ultraviolet of the correct combination of wavelengths, is used for the instant drying or curing of a vast range of photo setting resins, inks, varnishes, paints and adhesives.

The effect can be compared to two part fibre glass resins. The one part (resin) will remain a liquid until a chemical catalyst is mixed with it. This causes the molecules to start cross linking and the liquid becomes a solid plastic.

Photo setting resins have a resin base containing photo initiators. These resins will remain liquid until radiated with ultraviolet. This may be compared to the chemical catalyst in fibre glass resins.

When the photo initiators are bombarded with ultraviolet of the correct wavelength and strength, they immediately start the cross linking process which instantly turns the liquid into a solid.

A common application is curing of the high gloss varnish on magazine covers. At printing speeds of 15000 sheets per hour, the liquid resin is exposed to ultraviolet for less than 40 milliseconds and is completely dry or solid in that time.