It starts with the glass: Higher quality glass allows
more of the energy created inside the lamp to get out and do its work. The
critical measure of glass quality is referred to as “transmission” and relates
to the purity of the materials used to make the glass tubes. Low transmission
results in lower UV output; high transmission results in higher output.
If the glass purity is too great, unwanted wavelengths, like UVC, can contaminate
the output. Not too opaque, not too pure…the glass needs to be just right.
Select a phosphor or blend of two or more phosphors: The phosphor coating
on the inside of the tube is the source of the sunlamp’s tanning power.
Just as there are many roads to Rome, there are many phosphor blend combinations
that give similar spectral results, but not all individual phosphor components
are created equal. The best choice should be the phosphor that has the highest
purity, the highest efficiency (UV output per watt of power consumption),
the slowest natural depreciation (decline in output over time), and the
highest reliability in the manufacturing environment. The phosphor quality
needs to be just right.
Coat the glass tube with the phosphor: Make a suspension of phosphor and
a medium such as water; keep it constantly mixed so the phosphor remains
in suspension; coat the inside of the glass tube with a thin layer of this
suspension; dry, then bake. Coating thickness is a critical element: if
the coating is too thin, the UV output of the lamp suffers; too thick and
output is likewise diminished. There is an optimum thickness of the phosphor-coating
layer for each phosphor type and for each blend of phosphors. The bake-out
of the phosphor coating is also a critical process step. The baking time
and temperature must be carefully controlled in order to drive out any impurities
and properly set the adherence of the phosphor coating to the glass tube
– improper baking makes for lamps with diminished performance, starting
problems, or even dim areas. To take advantage of the quality of glass and
phosphor(s), the preparation and application of the coating must be done
just right.
Fill the glass tube with proper gasses: Inside a fluorescent lamp, the normal
air like we breathe is a contaminant, seriously degrading the lamp’s performance.
During sunlamp production, the normal air must be evacuated and replaced
with an inert gas. Argon or a mix of argon and neon are typical fill gasses
used in fluorescent sunlamps. The type of gas and the pressure of the gas
determine the electrical operating characteristics of the lamp. During the
exhaust/fill process, the tube is filled with the inert gas and a precisely
measured amount of mercury is dispensed before the tube is sealed. Improper
evacuation of air, the wrong mix of replacement gasses, incorrect fill pressure,
or the wrong mercury dose will all affect the operation and performance
of the lamp. To avoid starting and appearance problems, and to assure the
maximum UV output, the exhaust/fill process must be done just right.
Seal the lamp before adding the bases: Sealing the glass tube is the final
step to make it into a lamp. This seal is basically a glass weld that must
be hermetic, or airtight. Without tightly controlled processes and Quality
Control checks, the seal can finish with tiny, almost microscopic cracks.
If these cracks are large enough, outside air can be drawn (or leaked) into
the lamp because of the extremely low pressure within. Remember, air is
a contaminant if it gets inside the lamp. Lamps with small cracks that enlarge
as the lamp is heated and cooled during operation are called developmental
leakers (as the leak develops in time). In the worst cases, this shows up
as a lamp that is D.O.A. at your salon. In other cases it manifests as a
lamp that just goes out after a couple of tanning sessions. To avoid “no-lights”
or extreme early failure, this critical step has to be completed just right,
and verified through strict quality controls before the lamps are released
for shipment.
Wolff System: Doing it just right for more than a quarter century.
Cheri Mullenix A veteran member of the Wolff
System Technology Corp. Sales & Marketing team, Cheri Mullenix also
trains hundreds of salon professionals on Wolff sunlamp products each year.