Ceramic Metal Halide Lights
Ceramic Metal Halide grow lamps are made with an arc tube constructed of a ceramic composite instead of quartz or Poly Crystalline Alumina (PCA). This allows the tube to reach a higher temperature.
To achieve the lower operating temperature in HID lamps made with quartz or PCA, a combination of gases must be used that don’t necessarily produce the optimal light spectrum for photosynthesis.
The higher operating temperature of the ceramic tube allows for an ideal mixture of gases. This creates a fuller spectrum of light that increases the growth, overall health and yield of your plants.
A special CMH ballast is needed for ceramic metal halides. Not just any digital ballast will do. CMH lamps require a low frequency, which makes high-frequency digital ballasts incompatible.
The money you save on your power bill is the real bonus of switching to CMH grow lights. Although the initial cost of the system is more expensive than other HID systems on the market, CMH systems will save you money in the long run.
Some suppliers claim one 315W CMH is equivalent to one 1,000W HPS lamp in terms of yields. Others have reported that you need two 315W CMH lamps to produce the same yields as a 1,000W HPS.
The varying reports probably have to do with other elements in the garden and the gardener’s skill level, and the truth probably lies somewhere in the middle.
In any case, the general consensus is that your yield per watt is greater with ceramic metal halides, and you will be spending much less on electricity to power your lights. These lights also have a low heat output because of their low wattage.
One watt from a grow light creates about 4 British Thermal Units (BTUs) of heat that need to be cooled. Let’s say you have a small room with four 1,000W HPS grow lights. Your four lights alone create 16,000 BTUs of heat that need cooling.
If you trade those lights in for four CMH 630W fixtures, which will match, if not exceed, your current yields, you will only create 10,000 BTUs of heat. Your air conditioner won’t have to run as often, and you’ll see savings on your power bill.
The low heat output of CMHs make them an ideal choice for small grow spaces, such as closets and grow tents.
One final advantage ceramic metal halides bring to the table is their superior light quality compared to other HID lamps, which is due to a few factors.
First, they have a wider spectrum than other HID lamps, a result of the near-perfect, unique combination of salts, halides and gases used in the arc tube. This mixture creates a spectrum close to that of the sun and emits a stunning, crisp, white light.
In fact, the color rendering index (CRI) for ceramic lamps ranges from 90-92. To give you some perspective, the sun’s CRI is 100. HPS lamps range from 20-30, and metal halides range from 60-65.
The closer the CRI is to 100, the closer the spectrum is to that of the sun.
In terms of light quality, ceramics include ultraviolet and infrared rays in their spectrum, which plants love. The higher amounts of UV rays create stronger, woodier stalks. This means the growth and vigor of your plants will be unmatched, especially in the vegetative stage.
Due to the incredible growth CMHs produce, growers have reported great success when using silica supplements with these lights.
Silica helps with cell division and creates stronger cell walls, which makes the leaves, stalks and branches significantly stronger and better able to withstand the weight of the fruits.
As an added bonus, pests don’t like woody stalks because they are too hard to chew on. Compare it to eating a tender, juicy steak as opposed to eating an overcooked, dry steak. Which do you prefer?
Finally, CMH ballasts use square-wave technology. When you look at the graph on the back of the box your bulb is packaged in, notice the high peaks and low dips.
The peaks are an indicator of energy pushing out of the lamp. The low dips indicate light trying to travel to the next peak. You can see this with your own eyes when you take photos and videos of your growroom.
With most HID lights, you’ll see bands of light on your photos. The bands of light are the peaks in the graph, and the spaces between them indicate the dips.
With square-wave technology, there are fewer dips. A steadier beam of light is produced, which means your plants receive more light over their lives.
- Improved essential oil production
- Enhanced leaf, stem, root and shoot development
- Shorter inter nodes
Ceramic Metal Halide (CMH) lamps are a variation of Metal Halide (MH) lamps, but they are quite different. Instead of using a quartz tube, they use a ceramic arc tube, similar to a High Pressure Sodium (HPS) lamp.
Ceramic Discharge Metal Halide (CDM) is a different term for the same technology.
Light Emitting Ceramic (LEC) grow light, "LEC" is a brand name (trademark) for a model of grow light that uses Ceramic Metal Halide technology.
However, the term "LEC" is starting to become interchangeable with the term Ceramic Metal Halide (CMH) since they're both referring to the same technology.