What Is Metal Halide Grow Lighting?
Metal halide (MH) is a kind of high intensity discharge (HID) lamp considered one of the best alternative grow lights for growing greens. Metal halide grow lights give off a blue to white spectrum lighting, which makes them ideal to use for plants in their vegetative stage. The broad spectrum of light produced by metal halide bulbs helps plants develop stronger roots and healthier leaves.
MH grow lights have been around since the early 1960s and since then, they have been developed further for use in several applications such as street lighting and car headlamps. Metal halide lights are made just like mercury vapor lamps, but MH grow lights have additional metal halide compounds in the quartz arc tube, which is needed for color rendition and improved efficiency.
How Does Metal Halide Grow Lights Operate?
Some MH lights are made of mixed technology for better light output and to include more variations in the color spectrum, which results in a more complete solution. These grow lights have a high lumen output of around 100 lm per watt, with up to 20,000 hours of lamp life. They also have respectable degradation rates. This makes metal halide bulb systems valuable for gardens.
Metal halide lights produce significant heat onto the immediate area due to the nature of the processes that create light within the lamps. This is why you have to be careful when touching metal halide bulbs since one that has been running for a long time can give one a serious burn.
These MH bulbs also need a ballast to operate, just like ceramic metal halide (CMH) and high pressure sodium (HPS) bulbs. If the MH bulb runs on a constant voltage source (such as direct AC wiring), the electric current will total up until the bulb destroys itself.
When Should You Use a Metal Halide Grow Light?
Metal halides are best used for plants in their vegetative stage. The light spectrum produced by these grow lights are ideal for making plants develop lush and dense canopies even with very limited internodal spaces. This makes MH grow light systems perfect for growing greens such as peppers, spinach, lettuce, tomatoes, and flowering crops.
This type of grow light bulb system is also very adept at stopping stretching. There are various reasons why stretching happens, but the most common one is when the plants are not getting adequate light or if they are not receiving the right amount of blue light.
Mh lights are usually added by HPS growers into their gardens to provide blue spectrum lighting, which is essential in preventing the flowering crops from stretching during various stages of plant growth.
Why Metal Halide Grow Lighting Is The Best Option For You
Metal halide bulbs come in different wattages. The three most efficient of them are the 400-watts, 600-watts, and 100-watts. The 600-watts bulbs are the most commonly used by growers.
The size of the area that needs to be covered will determine the size of the MH light bulbs that you need.
For a coverage area of 2' x 2' and a hanging height of at least 7", you will need a 150-watt bulb.
For a coverage area of 2.5' x 2.5' and a hanging height of at least 10", you will need a 250-watt bulb.
For a coverage area of 3' x 3' and a hanging height of at least 12", you will need a 400-watt bulb.
For a coverage area of 4' x 4' and a hanging height of at least 16", you will need a 600-watt bulb.
For a coverage area of 5' x 5' and a hanging height of at least 22", you will need a 1000-watt bulb.
How High Should You Mount Your Metal Halide Grow Lights?
This will depend on the wattage of your metal halide bulbs and the size of your indoor gardening area. For instance, if you're using 400-watt light bulbs and your grow area is around 16 square feet, you should mount them at least 7 to 18 inches away from the tops of your growing plants.
If you're using 600-watt light bulbs in an area of 25 square feet, you should mount your standard MH bulbs at least 10 to 27 inches above your plants. Keep in mind too that if you're using this wattage of grow lights, you can combine them with HPS MH grow light systems of the same wattage.
If you have a large indoor gardening area, it's best to use 1000-watt metal halide grow lights, which should be mounted at least 12 to 31 inches above your plants.
The type of plants you are growing is also a factor in how high you should mount your MH grow lights.
How Many Plants Can You Grow Using Metal Halide Grow Lights?
There really is no set number when it comes to the number of plants you can grow using a single MH grow light. The deciding factors are the size of the space of your growing area and the type of plants that you are growing.
Experts do suggest that you can go by the wattage of the light bulbs in estimating how many you can grow. According to them, it's anywhere between 36 to 100 watts per plant, so that means you can grow 4 to 11 plants using just one grow light.
Do remember that this may not apply to all plants, so it's still necessary to do research about your specific plant type to know the amount of space you will need for growing and lighting.
What Should You Look For In Choosing Metal Halide Grow Lights?
It's important that you have adequate ventilation in your growing area since metal halide bulbs generate a fair amount of heat. Good ventilation ensures that your plants will be protected from drying out and burning. It also ensures the proper functioning of your equipment.
It's also necessary to use ballasts with MH grow lights. In order to get the right ones for your lights, check the ANSI code of each of your bulbs and then search for compatible ballasts using the three-letter code. The code on your bulb should match the code in your ballast.
You should also check the burn position needed for your metal halide bulb. Burn position refers to the position in which the light bulb can be installed safely. If you don't follow the correct positioning, the life span of your MH bulb can significantly decrease. Most MH bulbs are mounted either horizontally (parallel to the ground) or universally (any position).
You may encounter horizontal light bulbs that will need additional adjustment of plus or minus 15 degrees. Also, look into the type of base that your MH grow light accepts - it's either mogul or mogul extended bases.
How to Choose The Right Ballast For Your Metal Halide Grow Lights
When choosing the right ballast for your MH bulb, you need to take into account the bulb's color temperature - it can get affected by how the electrical system is powering your bulbs, as well as the bulb's manufacturing variances.
An underpowered MH bulb will provide a bluish light due to the evaporation of mercury alone. The opposite applies to an overpowered bulb, but bear in mind that this situation can be hazardous due to overpressure and overheating, which can result in an explosion.
This is why it's important to invest in the best electronic ballast you can afford if you are planning to dim your MH bulb. A high quality ballast will ensure the health of your light bulbs - it can detect the type of bulb you are running and adjust its functions accordingly. It will prolong your bulb's color rendition and life span.
Invest in a digital ballast that is dimmable for ease of use. It should also support both MH and HPS grow light bulbs. This will give your grow light more flexibility. The efficiency of your grow lights starts with your ballast, so make the effort to get a good one.
How Long Does It Take For Metal Halide Bulbs To Warm Up?
MH lamps need 10 to 15 minutes to reach 90 per cent of their full output after switching on. This is referred to as the war-up or run-up time. If your metal halide bulbs have been operating for a while and then you turned them off, you can't just turn them back on. You need to give the arc tube enough time to cool down before you can turn the lamps back on.
If you don't give them bulbs enough time to cool down, the lamp may not be able to restart. This is referred to as the restrike time. Traditional probe-start MH lamps have a restrike time of 15 minutes or longer. For pulse-start MH light bulbs, the restrike times can be more than twice as fast.
A perfect example here is the kind of lights that you see in stadiums. notice that MH lamps used during evening baseball games do not give off their full light output right away after starting. Stadiums have to turn these lights on in advance, even when it's still not dark enough, to actually reach the proper lighting.
When you see the MH lamps first get switched on in recreational fields or large stadiums, this is the warm-up period. The metal halide bulbs produce a faint glow that intensifies gradually the longer they stay on.
The mechanical construction of the light themselves is responsible for this. Because metal halide is an arc lamp, it works just like other HID lights such as high pressure sodium, fluorescent, and mercury vapor bulbs.
Inside the light tubes are special salts, which are a mixture of metal halides and mercury, that get vaporized into plasma while the bulb is operating. The light bulbs have to heat up tremendously, like several thousand degrees celsius, in order to operate.
The internal salts evaporate as the light heats up, which changes the quality of the light output. It will take time for the bulbs to reach their full power.
Comparing Metal Halide With HPS, LED, and Ceramic Metal Halide
Metal Halide VS HPS Grow Lights
There's no contest between these two types of HID lights given their respective light spectrum differences. They are each ideal for what they are intended for and it's not practical to compare which is better.
While metal halide light bulbs are the best for use in plants in vegetative stages and produce healthy leaves and tight internodal spaces, HPS light bulbs are better for plants in the flowering stage, specifically for more fruit growth and flower output.
Both metal halide and HPS grow lights are in a similar price range, with HPS bulbs tending to have slower degradation rates.
Metal Halide VS LED Grow Lights
Theoretically, LED technology is superior to all the other HID technology given the nature of how LED produces light. LED lighting can target any part of the Photosynthetic Response Spectrum. It also avoids wasting energy and under-utilizing light.
Lower heat output is another big advantage of LEDs over MH lights, most especially since LED lights operate in a comparatively passive manner. This is not usually doable when using MH bulbs. LEDs can also last longer, thus needing less replacement.
However, MH bulbs have it over LEDs when it comes to low introductory price, accessibility, and track record in ensuring the healthiest growth for greens.
Metal Halide VS Ceramic Metal Halide Grow Lights
MH and CMH may look the same, but they are not. CMH has certain advantages when it comes to overall light spectrum, which can be better than MH grow lights. CMH grow lights have a higher white and red light output overall. Their lights are also cooler and give off more PAR light watt per watt.
However, MH grow lights are commonly more affordable, which is certainly a plus for growers under limited budgets.
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