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What is HID?

HID is a high intensity discharge lamp.  They have electrodes positioned at either end of the bulb with a gas and metal filled tube causing the vapors to be converted into light.  HIDs do not use phosphor.  HID lamps are filled with a gas at a very high rate of pressure, the electrical arc, gasses and metals, in an HID lamp are contained in what is known as the arc tube.  The arc tube is made of either quartz or ceramic and are housed within the glass bulb.

All HID lamps require a ballast to control the electrical current, very similar to fluorescents.  Select HID lamps will also require an igniter which produces a high voltage to run through the arc tube and start the HID


HID lamps require a burn in period of approximately 100 hours to reach their full brightness.  You will most likely see a shift or variations in colors during this period until the HID stabilizes.  The color and brightness will then remain consistent until the bulb ages.  Towards the end of its life, yes HIDs do age and the chemical changes can also cause color shifting.  It is recommended to change all HID lamps that have started to change colors.  HIDs also use the kelvin scale to determine their color.  They are available in warm – white and bright white options.

There are three types of HID or high intensity discharge lamps.  They are available in Mercury Vapor, Metal Halide or High Pressure Sodium and come in several different shapes.  ED17, ET, ET18, ET23.5, Tubular, BT28, BT37, BT56PAR, double ended and single ended  HIDs are all very common.