Great questions. First, let’s talk about how a low-pressure sunlamp works. The glass tube has a thin phosphor coating on the inside, and contains a small amount of inert gas and mercury. When power is applied to the lamp, emissive material (a chemical coating) sputters from the cathodes at each end and inside the lamp. These emissions assist in the ignition of an electric arc between the cathodes at opposite ends. The mercury vaporizes as a result of the arc, contributing its properties to the arc stream. The phosphors are “excited” by the ultraviolet energy of the mercury, causing them to fluoresce.
Basically, a sunlamp is composed of glass, metals, gas and phosphors. When we at Wolff System speak about performance depreciation of sunlamps, we are referring to the known characteristics of the phosphor within the sealed glass tube that makes up the lamp.
When a lamp is started and operated, the depreciation process begins. The phosphor will weaken as the lamp continues to operate, producing less UV output. This is a natural result of the interaction between the phosphor material and the electric arc from one end of the lamp to the other, plus a phosphor-weakening factor is present in the form of heat. This natural decline in output (from the degradation of the phosphor’s efficacy) leads us to the service-life ratings we publish… service-life equals that point where the lamp’s output has declined 30 percent from when it was new.
Once a sunlamp is turned off, the depreciation process is halted until the next time the lamp is started. Unlike with bread or milk, there is nothing organic in a sunlamp that will fail or spoil over time. Our service-life ratings speak to lamp-on hours, not elapsed time. Some lamp applications may take ten years to collect 1,000 service hours; a busy tanning salon may do that in a few months. Burn a sunlamp for one hour then turn it off, bury it in a time capsule and unearth it 100 years later – it still has only one hour of use and is the same as when it was put away.
Cheri Mullenix is a veteran member of the
Wolff System Technology Corp. Sales and Marketing team.