• Most people are familiar with the glow-in-the-dark UV black light posters that were popular a few decades ago. Ultraviolet lights have many uses, including many commercial uses that go far beyond entertainment value. Among these are water purification; medical diagnosis and treatment; forgery detection, and authentication of antiques.
  
  

Forgery Detection

• Art and antique dealers commonly use "black light" to authenticate antiques and artwork, to determine age, and to detect whether items have been repaired or altered. U.S. currency and official documents are manufactured using dyes that can only be seen under ultraviolet light. The currency contains fluorescent inks, with different colors used for each denomination. The color and location of the security thread in U.S. currency is unique to the value of the bill.
  
  

Glassware

• Specialty collectible glass can be authenticated using black lights, because of the older paints and materials that were used during specific eras.
  
  

Hand-stamping

• Since visible inks can be duplicated, some nightclub managers use invisible inks for hand-stamping that is detectable only under UV light. This allows club personnel to know which patrons have paid the cover charge and enables patrons to temporarily leave and then return without paying another cover charge.
  
  

Fabric Authentication

• Modern synthetic fabrics, such as polyester and rayon, will fluoresce under ultraviolet light. Vintage fabrics do not. Even if old fabrics are used to create a garment, the new threads would show up under UV light.
  
  

Forensics

• Ultraviolet light is used by law-enforcement personnel to detect evidence of bodily fluids at crime scenes. Fire inspectors also sometimes use it to determine the cause of a fire.
  
  

Mineral Identification

• Jewelers and rock collectors can use black light to identify certain minerals and gemstones.
  
  

Pet Stains

• Once pet stains have dried on a carpet, the smell may remain, but the spot may be undetectable in a corner of a room or under a bed. UV lights will reveal the stain so that it can be removed.
  
  

Bacteria

• Certain bacteria, such as salmonella, will glow under black light. In addition, some bacteria can be chemically altered so that they also can be revealed under black light.
  
  

Decorative Uses

• Fluorescent paints and inks have long been used used to make posters and other novelty items so that they will glow in the dark and display with more brilliance under black light.
  
  

Medical Uses

• Exposure to ultraviolet light is used in the treatment of skin disorders such as psoriasis, jaundice and vitiligo, as well as cancer detection and treatment of arthritis and blood toxins.
  
  

Scorpion Detection

• Scorpions can camouflage themselves in their surroundings. However, many species are detectable after dark using black light -- important knowledge in regions where scorpions are often present.
  
  

Water Purification

• UV lights are used in large and small drinking water systems for water purification. UV filters can be used in place of chlorination in home water systems to ensure well water is free of bacterial contamination while avoiding introduction of chemicals, their byproducts, tastes and smells.