Publication Type:Conference Paper
Source:Tradition and innovation: advances in conservation: contributions to the Melbourne Congress, 10-14 October 2000, p.133-136 (2000)
Keywords:fluorescence, history of technology, optical brightener, whitening
In the early 20th century, a class of chemicals was identified that could increase whitening by the action of fluorescence. These materials, often called colorless dyes, are known as fluorescent whitening agents, optical bleaches, or optical brighteners. Optical brighteners are a group of molecules that absorb light predominantly in the ultraviolet range and emit light in the visible range, thereby causing a brightening of the substrate by emitting more than 100% of the incident visible light. These materials were first used in food packaging and x-ray film enclosures to prevent deterioration caused by ultraviolet light. Soon their whitening properties were exploited, and brighteners were added to numerous commercial materials, fostering a taste for "whiter than white" papers, textiles, and nonyellowing plastics. In the conservation and preservation of works of art and cultural property, the behavior and aging of optical brighteners play an important role, particularly in works from the second half of the 20th century. The technology and development of these materials and their chemistry affect their longevity, appearance, and interaction with conservation procedures.