Wood’s lamp… to see the invisible

     Being able to see what isn’t visible to naked–eye has been one of the wishes that mankind has been able to satisfy gradually, over the centuries. To do this we have built many tools and it was as if our senses are enhanced. Telescopes, radioscopy, microscopes, seismographs, litmus paper... the list is rich and growing. 

     In the group of data collection and measurement instruments there is also the ultraviolet light (Wood’s lamp or black light). This valuable tool was invented by the American inventor Robert Williams Wood (1868–1955). The lamp emits ultraviolet rays which aren’t harmful to humans and able to highlight things that escape to a normal vision. The principle on which is based the Wood’s lamp is to excite the fluorescent and phosphorescent pigments present on fabrics, paper, bacteria, minerals, bills (printed on paper containing fluorescent fibrils reactive under UV light).

     The fields of application are manifold: biology, mineralogy, antiques, restoration, quality food analysis, checking bills. There’s a range of applications that could make red–hot the minds of those who have always dreamed of living an adventure as a forensic agent: this is the identification of organic liquids stains or traces. In dermatology this lamp is suitable to detect fungal infections or skin diseases such as vitiligo. In the foodindustry we can detect the occurrence of fungus that affect the quality of food. In microbiology the UV light makes fluorescent bacteria. In the field of paintings restoration Wood’s light is useful to find out the original colors that the age has deteriorated. We can also define if a painting has undergone previous restorations. There’s also a recreational use in clubs, amusement parks and tourist attractions in order to create fluorescence effects enhancing the white color of eyes, teeth and clothes (for Halloween if you wear a skeleton dressed the effect will be awesome… or frightening).

     The sector in which I was directly involved is paleography. In the study of ancient documents, parchments, registers, records, papyrus, we come across in the most feared opponent: the deterioration due to time or to negligence. But those portions of the manuscript text that appears lost forever, actually can be retrieved in a new light, the light emitted by the Wood’s lamp.