Optical Brightening Agents (OBA) or Fluorescent Whitening Agents (FWA) is added to many substrates to reduce yellowing, improve whiteness and enhance the brightness of the product. Optical whiteners function by absorbing ultraviolet radiation and re-emitting blue light. The emitted blue light will reduce the yellow color of the substrate and impart a pleasing whiter-than-white appearance. Optical brighteners give more intensity to some colors as well.