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

light. Phosphor-coated bulbs used to be popular among growers, but this trend has waned over the last ten years because they are not as bright as clear bulbs.
    The 1000-watt super clear halides are the most common halides used to grow marijuana in North America. Compare energy distribution charts and lumen output of all lamps to decide which lamp offers the most light for your garden. Typically, a home grower starts with one super metal halide.
Construction and Operation
    Metal halide lamps produce light by passing or arcing electricity through vaporized argon gas, mercury, thorium iodide, sodium iodide, and scandium iode within the quartz arc tube. After they are in their proper concentrations in the arc tube, the characteristic bright white light is emitted. This process takes about three to five minutes. The metal halide arc system is very complex and requires a seasoning period of 100 hours operation for all of its components to stabilize. If a power surge occurs and the lamp goes out or is turned off, it will take five to fifteen minutes for the gases inside the arc tube to cool before restarting.

Metal Halide Bulbs
    The outer bulb functions as a protective jacket that contains the arc tube and starting mechanism, keeping them in a constant environment as well as absorbing ultraviolet radiation. Protective glasses that filter out ultraviolet rays are a good idea if you spend much time in the grow room, or if you are prone to staring at the HID!
    When the lamp is started, incredible voltage is necessary for the initial ionization process to take place. Turning the lamp on and off more than once a day causes unnecessary stress on the HID system and will shorten its life. It is best to start the lamp only once a day, and always use a timer.
    The metal halides operate most efficiently in a vertical ± 15-degree position (see diagram page 202). When operated in positions other than ± 15-degrees of vertical, lamp wattage, lumen output, and life decrease; the arc bends, creating non-uniform heating of the arc tube wall, resulting in less efficient operation and shorter life. There are special lamps made to operate in the horizontal or any other position other than ± 15 degrees (see diagram page 202).These bulbs have “HOR” stamped on the crown or base which refers to horizontal.
Lumen Maintenance and Life
    The average life of a halide is about 12,000 hours, almost two years of daily operation at 18 hours per day. Many will last even longer. The lamp reaches the end of its life when it fails to start or come up to full brilliance. This is usually caused by deterioration of lamp electrodes over time, loss of transmission of the arc tube from blackening, or shifts in the chemical balance of the metals in the arc tube. Do not wait until the bulb is burned out before changing it. An old bulb is inefficient and costly. Replace bulbs every 10-12 months or 5000 hours. Electrode deterioration is greatest during start-up. Bulbs are cheap! Throw another one in, and you will be happy!
    The halide may produce a stroboscopic (flashing) effect. The light will appear bright, then dim, bright, dim, etc. This flashing is the result of the arc being extinguished 120 times every second. Illumination usually remains constant, but it may pulsate a little. This is normal and nothing to worry about.
Metal Halide Ballasts
    Read “About Ballasts.” The ballast for a 1000-watt halide will operate standard, clear, and phosphor-coated and super, clear, and phosphor-coated halides on a 120 or 240-volt current. Different ballasts are required for each lamp wattage; 150, 250, 400, 1000, 1100, and 1500. The ballast for each wattage will operate all halides (super or standard, clear or phosphor coated) of the same wattage. Each ballast must be specifically designed for the 150, 250, 400, 1000, 1100, or 1500-watt halides, because their starting and operating requirements are unique.
Metal Halide Bulbs
    Universal metal halide bulbs designed to operate in any position, vertical or horizontal, supply up to ten percent less light and often have a shorter life.
    SunMaster Warm Deluxe Grow Lamps emit balanced light similar to a 3000 Kelvin source. The enhanced orange-red component promotes flowering, stem elongation, and germination while a rich blue content assures healthy vegetative growth.
    Venture manufactures the AgroSun for Hydrofarm. It is an enhanced metal halide bulb with more yellow/orange in the spectrum. To find out more about this lamp,