4 Things To Consider When Buying a Metal Halide Bulb

4 Things To Consider When Buying a Metal Halide Bulb

Metal halide bulbs are powerful bulbs that are typically found in parking lots, sports game lighting, and retail stores. They radiate a white, bright light, and their CRI, or color rendering index, are typically greater than other bulbs. Because these bulbs are so powerful, check out these four things to consider when buying a metal halide bulb.

Protected vs. Unprotected Arc Tubes

Take into consideration whether the bulbs have protected or unprotected arc tubes. An arc tube houses the electric arc which is filled with gas and metal salts. When a bulb is turned on, heat is created. In turn, the metal salts are evaporated, and the light intensifies. A metal halide bulb with a protected arc has a hard casing around the arc and can be used in light fixtures that are enclosed or are open-rated. Due to its neck size, there can be multiple installation applications.

In contrast, a bulb with an unprotected arc can only be used in enclosed light fixtures that can hold an arc tube that have the possibility to rupture. Bulbs with unprotected arcs are usually wider, and the wires are closer together. If they are in an enclosed fixture, they are cheap and safe to use. If you need replacement options, check out these 400-watt metal halide LED replacements.

Probe-Start vs. Pulse-Start

There are two different types of start processes for MH bulbs: probe-start and pulse-start. The probe-start process is a more traditional system and is therefore usually more affordable. Probe-start uses electrodes to create gas in order to keep the light lit. Unfortunately, it is prone to tungsten buildup that can blacken the light and decrease its brightness.

On the other hand, pulse-start lamps are new to the market and a little more expensive. Due to their electrodes and high voltage ignitor, they reach their brightness potential quicker than probe-start. Their overall lamp life lasts longer than a probe-start, too.

Burn Position

Metal halide HID lamps have a specific burn position; they operate best at specific angles. Thus, if they are facing the wrong directions, they may be less efficient, resulting in more frequent replacement. Continue to keep in mind the different burn positions, such as horizontal, vertical, and universal. Vertical is usually separated by a base for either up or down, whereas universal can be operated at any angle.

Quartz vs. Ceramic Arc Tubes

The arc tube can be made of two different kinds of material—quartz and ceramic. Older versions of MH bulbs use quartz. Quartz is a great material for lower wattage at higher temperatures. Newer versions of MH bulbs use ceramic arc tubes, which allow higher wattage and temperatures. Additionally, ceramic arc tubes help achieve a better overall efficacy.


These four things to consider when buying a metal halide bulb may save you time and money, as well as help you achieve the lighting results you desire. From tube type and tube material to burn time and start type, there are multiple factors to keep in mind next time you purchase one of these powerful bulbs.

Feb 23rd 2022 Ralph McGinnis

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