| Metal halide grow lights create fantastic light under | | | | color-rendering index, on a scale of zero to 100. |
| which your plants will thrive. These grow lights are | | | | This index ranks lights to show how well or poorly |
| a HID, or high-intensity discharge, light. They are | | | | they reproduce colors of objects being lit by the |
| small grow lamps that produce a lot of light, and | | | | lamp. |
| yet are more efficient to run than either | | | | 100 is the best rating, and zero the worst. |
| incandescent or fluorescent light bulbs. Indoor | | | | Therefore, an 80 is reflective of a very good |
| gardeners and hydroponics enthusiasts get great | | | | quality white light. In terms of correlated color |
| results with their plants when they use metal | | | | temperature, MH grow lights can range from |
| halide lights. | | | | 3,000 K to 20,000 K. 3,000 is in the yellow range |
| Metal halide lamps are made up of several | | | | of the spectrum, while 20,000 is in the blue range. |
| different parts. There are tungsten electrodes | | | | (K refers to the Kelvin temperature scale.) In |
| which are connected to a quartz arc tube, where | | | | terms of comparison, daylight registers in at |
| the light is produced. Inside the arc tube is where | | | | 6,500 K, whereas a television screen is at 9,300 K |
| you will find mercury vapor, different metals and | | | | and moonlight is at 4,100 K. If you are an indoor |
| noble gas, all of which play a part in creating the | | | | gardener, you are trying to recreate daylight in |
| light produced by MH grow lights. The arc tube is | | | | order for your plants to thrive, so you will want a |
| covered by a glass bulb. There is a metal base, | | | | bulb as close to daylight's 6,500 K as possible. |
| and a connection to the power source. Some | | | | Light produced by a grow lamp can fall at |
| metal halide grow lights use an arc tube made of | | | | different spots on the electromagnetic spectrum. |
| alumina or aluminum oxide, as well. This type of | | | | Some lights lean more toward the blue end of |
| grow light requires the use of a ballast to control | | | | spectrum, while others land on the orange and |
| the flow of the current through the arc tube in | | | | red end. This matters to the indoor gardener, |
| order for the grow lamp to function properly. | | | | because baby plants need light in the blue |
| Each different type of grow light has a particular | | | | spectrum in order to grow well. If you want a |
| color-rendering index and correlated color | | | | mature plant to produce fruit or flowers, then you |
| temperature. This is true of the metal halide grow | | | | will need lights in the red and orange spectrum. |
| lights. Some of these lamps have an 80 | | | | |