Speciality Shop
Click on Lightee to return to the Home Page
Fluorescent Blacklights
BL in the tube designation (F40T12/BL) means blacklight, which is a fluorescent lamp with a phosphor that emits the longest largely invisible UV wavelengths that are both efficiently and fairly cheaply possible. The phosphor seems to emit a band of UV mainly from 350 to 370 nanometers, in the UV-A range.
BLB means blacklight-blue, which differs from blacklight only in that the glass tube of this lamp is darkly tinted with something with a dark violet-blue color to absorb most visible light. Most UV gets through this, along with much of the dimly visible deep-violet 404.7 nanometer line of mercury. Most of the violetish-blue 435.8-nanometer line is absorbed, but enough of this wavelength gets through to largely dominate the color of the visible light from this lamp. Longer visible light wavelengths do not significantly penetrate the BLB’s very deep violet-blue glass, which is known as Wood’s glass. The UV is the same as that of the BL lamp, being mostly between 350 and 370 nanometers.
There is a 350BL blacklight lamp, using a different phosphor that emits a band of slightly shorter UV wavelengths in the UV-A range. The reasoning for this lamp is that it is supposedly optimized for attracting insects. These lamps are one variety of UV lamps used in electric bug killers.
There are other UV fluorescent lamps. There are at least two different UV/deep violet emitting fluorescent lamps used mainly in the graphic arts industry, emitting mainly wavelengths between 360 and 420 nanometers. Possibly one of these is also used in bug killers. I have noticed one kind of UV fluorescent lamp for bug killers with a broadish band phosphor with significant output from the 360 nanometer range (maybe also shorter) into visible wavelengths around 410-420 nanometers or so.
There is an even shorter UV-A lamp used for sun tanning purposes. I would guess the phosphor emits mainly within 315-to 345-nanometer range. One brand of such lamps is “Uvalux”.
There is even a UV-B emitting fluorescent lamp. Its phosphor emits mostly UV-B wavelengths, 280 to 315 nanometers. It is mainly for special medicinal purposes. Exposing skin to UV-B causes erythema, which is to some extent a burn reaction of the skin to a slightly destructive irritant. Use of UV-B largely limits this to outer layers of the skin (perhaps mainly the epidermis) and to parts of the body where skin is thinner. UV-A wavelengths just over 315 nanometers can also cause sunburn, but they are more penetrating and can affect the dermis. Please note that the deadliest varieties of skin cancer usually most easily caused by UV-B rays.
There are clear UV- emitting lamps made of a special glass that lets through the main shortwave UV (UV-C) mercury radiation at 253.7 nanometers. These lamps are marketed as germicidal lamps, and ones in standard fluorescent lamp sizes have part numbers that start with G instead of F. These lamps will work in standard fluorescent lamp fixtures. Cold-cathode germicidal lamps are also in use; these somewhat resembles neon tubing.
Be warned that the shortwave UV emitted by germicidal lamps is intended to be dangerous to living cells and is hazardous, especially to the conjunctiva of eyes. Signs of injury by the UV are often delayed, often first becoming apparent several minutes after exposure and peaking out a half hour to several hours afterwards.
Copyright ©: 2007
All Rights Reserved