Printing inks that both emit and reflect light. Generally, these inks are brighter and more opaque than traditional inks. Using one or more fluorescent inks can actually brighten a printed image - especially four-colour process printing on uncoated stock. On the down side, fluorescent inks are not colourfast and will fade in bright light and sunlight over time. They can also have a negative effect on dot gain and trapping, making the printing less sharp and without as much detail.