Optical brighteners have been used for many years to improve the colour of various plastics. They are able to mask inherent yellowness in discoloured polymers or impart unique, robust colour to speciality plastic products.

They work by absorbing UV light and giving off a blue glow, which covers the natural yellow colour that many plastics develop. This makes the plastic look cleaner, fresher, and brighter. These masterbatches are mainly used to hide yellowing and improve the appearance of plastic products.