Looking for bulbs that are black or you actually need ultraviolet light bulbs?
There is actually no black light. The absence of light is black and we call it darkness. And for darkness we need no bulbs. What is referred as black light bulb is actually a ultraviolet (UV) light bulb. The glass of such light bulbs is usually dark which makes them look black. Ultraviolet light is part of electromagnetic spectrum close to visible light. It is called ultraviolet because it is located close to violet light but has shorter wavelengths. Ultraviolet bulbs emit only small amount of visible light, most of the light spectrum lies in the ultraviolet A region (UVA). This kind of ultraviolet light is considered as safe since mainly UVB and UVC ultraviolet light causes skin cancer.
Ultraviolet light bulbs are similar to normal ones. For example, the core of normal fluorescent lamp is ultraviolet light. The lamp contains mercury vapors which are excited by electricity. Excited mercury atoms emit ultraviolet light which then causes phosphor coating to fluoresce. If you replace phosphor coating with ultraviolet filter or use only one type of phosphor that emits ultraviolet light you get a simple black light bulb. Incandescent bulbs can also be used for ultraviolet light. Such bulbs use Wood’s glass which filters out visible light and only passes through ultraviolet components. Many commercial ultraviolet bulbs use Wood’s glass for light filtering.
Ultraviolet (UV) light is used in various fields of science, shops, night clubs and at home. Black light can be used to detect counterfeited money since real banknotes contain fluorescent markings that are visible only under UV light. Counterfeit money detector is a very simple lamp with UV light bulb. Ultraviolet light is used in molecular biology to mark desired parts for visualization, to detect cracks in metal structures and has also many applications in medicine. Fluorescent pens can be used to invisibly mark items that could be stolen – those markings become clearly visible under ultraviolet light. UV light bulbs are used also in some night clubs to make white clothes glow in the dark.
UV light bulbs which emit UV light below 200 nm can produce ozone (O3) from oxygen in the air. Ozone is used to deodorize rooms and for water purification. It is interesting that ozone layer in the upper atmosphere absorbs dangerous UV radiation and prevents it to reach the earth and damage live beings. On the one hand we try to limit use of substances that destroy ozone layer – a natural UV radiation protection, on the other hand we make various bulbs to create UV radiation. A typical useful use of otherwise harmful UV radiation is sterilization. High intensity UV light around 250 nm (UVC) has germicidal properties. It can very effectively destroy microorganisms. Such UV light bulbs are widely used in sterilization devices and in UV water treatment devices.
Black light bulbs can also be used at home. With their help we can easily locate pet urine stains. This is very helpful since pet odor remover can not help if you don’t know where the stain is. The cost of ultraviolet bulbs is only slightly higher than the cost on normal bulbs for visible light. Lamps for home use can be found in most shops that sell lighting gear. Many specialized shops offer also other black light gear: bulbs, fluorescent pens, invisible ink, special colors, posters, balloons, candles, etc.Black light bulbs, UV light bulbs or ultraviolet light bulbs all refer to a light bulb which mainly generates invisible light, has many practical uses and can be also used for decorative purposes.