Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

Spectrum GroLux. The Standard GroLux is the lamp to use for starting clones or seedlings. It is designed for use as the only source of light, having the full spectrum necessary for photosynthesis and chlorophyll production. The Wide Spectrum GroLux is designed to supplement natural light and covers the blue to far-red regions. Westinghouse has the AgroLight that produces a very similar spectrum to the sun. Warm White and Cool White bulbs used together make excellent lamps to root clones.

Color spectrum of Mercury Vapor Spectrum bulb
     
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Full Spectrum?
    The term full-spectrum was coined in the 1960s by photo-biologist Dr. John Ott to describe electric light sources that simulate the visible and UV spectrum of natural light. Today there are many fluorescent lamps advertised as “full-spectrum.” All fluorescent bulbs marketed as “full-spectrum” grow lights are tri-phosphor-coated. Until photo-biologist Dr John Ott began producing and selling the first “color-corrected” bulbs, all fluorescent lamps were halo-phosphor or deluxe halo-phosphor blends, which did not render the reds well. Tri-phosphor-coated lamps emit the visible light spectrum in spectrums from 2700 K to 6400 K. They simulate colors by mixing the three colors associated with the three cone types in our eyes “specially formulated to replicate all the wavelengths in the visible spectrum.”
    The term “full-spectrum” has been successful to help sell overpriced lights. Now the market is rampant with hype about the lights. Resellers purchase tri-phosphor bulbs from manufacturers and market them as “Grow Lites.” Major lamp manufacturers do not sell tri-phosphor-coated lights as “full-spectrum.”
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    Fluorescent bulbs are further classified by diameter and come in the sizes T12 (1.5 inch [5 cm]), T8 (1 inch [3 cm]), T5 (0.625 inch [1.5 cm]) and CFL (see “Compact Fluorescent Lamps”). The T12 uses old-fashioned magnetic ballasts. The T8 and the T5 (technically CFLs) use electronic ballasts. Growers prefer slimmer T8 and T5 bulbs with electronic ballasts because they run cooler, electricity cycles faster, and lights do not flicker.
    The average lumen output of a 40-watt T12 is 2800 lumens, about 68 lumens per watt.
    A 32-watt T8 bulb yields 100 lumens per watt and cranks out 100 average lumens.
    A 54-watt T5 throws 5000 average lumens, which means it produces 92 lumens per watt.
Construction and Operation
    Fluorescent lamps create light by passing electricity through gaseous vapor under low pressure.
    Like the HID family, fluorescents require an appropriate fixture containing a small ballast to regulate electricity and household electrical current. The fixture is usually integrated into the reflective hood. There are several types of fixtures. The most common fluorescent bulbs used for growing are hooked to sockets with bi-pin connectors. If purchasing new tubes, make sure the bulb fits the fixture. The fixture may contain one, two, or four tubes.
    A ballast radiates almost all heat produced by the system. The ballast is located far enough away from fluorescent tubes that plants can actually touch them without being burned.
    Ballasts will normally last 10-12 years. Used fluorescent fixtures are generally acceptable. The end of a magnetic ballast’s life is usually accompanied by smoke and a miserable chemical odor. Electronic ballasts simply stop. When the ballast burns out, remove it and buy a new one to replace it. Be very careful if the ballast has brown slime or sludge on or around it. This sludge could contain carcinogenic PCBs. If the ballast contains the sludge, dispose of it in an approved location. Most modern fluorescents are self-starting, but older fluorescents require a special starter. This starter may be integrated into the body of the fixture and hidden from view, or be a small metal tube (about 1 inch [3 cm] in diameter and 0.5-inch long [1 cm]), located at the end of the fixture on the underside. The latter starters are replaceable, while the former require a trip to the electrical store.
    If your fluorescent fixture does not work, and you are not well versed in fluorescent troubleshooting, take it to the nearest electric store and ask for advice. Make sure they test each component and tell you why it should be replaced. It might be less expensive to buy another fixture.
    The tubular glass bulb is coated on the inside with phosphor. The mix of phosphorescent chemicals in the coating and the gases contained