Photoinitiator is component in a UV ink that initiates curing by absorbing UV light and generating free radicals that react with double bonds causing a chain reaction and polymerization. This is the process that cures UV ink instantly. The amount of photoinitators in the ink and the amount of UV light exposure determine the level of cure. Too much photoinitiator in the ink can cause the ink to begin to cure from UV light emitted by fluorescent room lighting.