What is a low-pressure sunlamp?
Low-pressure sunlamps are utilized most prevalently in our industry by a large margin. They are usually 5- or 6-foot, linear glass tubes, employing fluorescent light technology. The term “low-pressure” (LP) refers to the pressure contained within the glass tube. This pressure amounts to somewhat less than one atmosphere, actually a slight vacuum. When a lamp is broken, it collapses – or implodes – as the external positive atmosphere rushes to fill the space within the lamp at negative atmosphere.
When low-pressure lamps receive the proper electrical voltage and current, an arc is created from one end of the lamp to the other. This arc vaporizes a small amount of mercury in the lamp, resulting in the emission of ultraviolet light. A thin coating of phosphor (or a blend of phosphors) on the inside of the lamp wall is excited by the mercury’s UV emissions. The phosphor used to make the sunlamp determines its UV output; the phosphor converts mercury output to the UV tanning spectrum common to LP sunlamps (Figure 1). Most of the UV light emissions are not visible; this is the UV needed to stimulate the tanning process. A small amount of the emissions is visible, but while only a small portion of the visible light contributes to pigment darkening, it is a handy way to tell that the sunlamp is functioning.
The light emitted by LP sunlamps is a combination of UVB (280-320 nanometers), UVA2 (320-340nm) and UVA1 (340-400nm) plus the small component of visible light described earlier. Differences in the effectiveness between one lamp type and another are modified through adjustment of the phosphors. UVB stimulates melanin production and can burn the skin if overexposed; UVA2 acts a lot like UVB, with melanin production and some pigment darkening; it is also closely associated with elastosis (photoaging, wrinkles). UVA1 penetrates deeper past the surface skin layer and is primarily responsible for pigment darkening. The newer lamps focus on providing enough UVB to stimulate the melanin and aid in production of vitamin D, with plenty of UVA1 and less of UVA2.
Any questions or comments about this topic, as well as suggestions for future articles, should be emailed to sales@wolffsys.com or call 800.959.6533.
