An inexpensive and easy to use longwave black light is a great tool for quickly identifying reprints and fakes of Pre World War II paper material. This includes trading cards, photographs, programs, posters, postcards, tickets and anything made of paper.
A black light is effective in identifying of many, though not all, modern paper stocks.
Starting in the late 1940s, manufacturers of many products began adding optical brighteners and other new chemicals to their products. Optical brighteners are invisible dyes that fluoresce brightly under ultraviolet light. They were used to make products appear brighter in normal daylight, which contains some ultraviolet light. Optical brighteners were added to laundry detergent and clothes to help drown out stains and to give the often advertised `whiter than white whites.’ Optical brighteners were added to plastic toys to makes them brighter and more colorful. Paper manufacturers joined the act as well, adding optical brighteners to many, though not all of their white papers stocks.
A black light can identify many trading cards, posters, photos and other paper items that contain optical brighteners. In a dark room and under black light optical brighteners will usually fluoresce a very bright light blue or bright white. To find out what this looks like shine a recently made white trading card, snapshot or most types of today’s printing paper under a black light.
If paper stock fluoresces very bright as just described, it almost certainly was made after the mid 1940s.
It is important to note that not all modern papers will fluoresce this way as optical brighteners are not added to all modern paper. For example, many modern wirephotos have no optical brighteners. This means that if a paper doesn’t fluoresce brightly this does not mean it is necessarily old. However, with few exceptions, if a paper object fluoresces very brightly, it could not have been made before World War II. It is important that the collector gain practical experience. This means using a black light to examine and compare the fluorescence of a variety of items. With photographs, make sure you shine the black light on all sides and edges. This is because the gelatin or other coating on the front of the paper often prevents the front from fluorescing.
The beauty of this black light test is you can use it on items you aren’t an expert on. You may be no expert on 1920s German Expressionist movie posters or 1890s Canadian fishing industry pamphlets, but you can still identify many modern reprints.