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3

Light Sources

Perhaps the single most important influence on the success of the indoor grow industry is the advance in electric lighting, especially the High Intensity Discharge, or HID systems. These included the metal halide and high pressure sodium systems that revolutionized the scene. The metal halide arrived in approximately 1978, and the high pressure sodium followed about a year later. These systems provided an indoor light source that could deliver an adequate amount of light, and full bandwidth of spectrum necessary to mass produce high quality product. Before these systems, the best light source product available was the fluorescent.

Fluorescents

Fluorescent systems come in many sizes and wattage increments, but the most common sizes are four- and eight-foot bulbs. The standard four-foot bulb is 40 watts, and the eight-foot is 80 watts. These systems often come with two or four parallel bulbs. Fluorescent systems are still a must-have for any form of commercial production. Seedlings and clones thrive when placed within one to five inches of the bulb. The fluorescent tends to promote root growth along with foliar spread. The “cool” light seems to be just the right thing for freshly cut and rooting clones.

It is important to never let the leaves of the plant touch the fluorescent bulb, which results in burning of the leaf; however, it is, recommended to let the plants get as close as possible to the bulb without touching. Therefore, regular checking is crucial to optimum success. It is also standard procedure for fluorescent systems to be hung by hooks and chains to facilitate ease of raising and lowering, and for the plants to be arranged by height.

The problem with fluorescent systems is that the intensity of light diminishes exponentially with distance from the bulb. Within one to five inches from the bulb, the concentration of light is strong enough to produce sufficient growth. But beyond five inches, the intensity of the light drops off sharply. A successful fluorescent system ends up creating a canopy approximately four to six inches thick, which spreads out and up to consume as much of the potent light as possible while shading out most undergrowth. The experienced fluorescent farmer knows how to prune away the unwanted undergrowth to optimize production and stimulate the growth of the canopy. This canopy is capable of providing fully mature finished product, but the buds are more often than not airy and lightweight—usually rather wispy.

I have seen fluorescent systems used to complete maturation with good quality results. However, quantity lacked considerably. It needs to be noted that fluorescent systems are perfectly capable of producing small quantities of high quality product. Production may be somewhat increased by setting up more fluorescent systems along the sides, as well as the top of the garden. Therefore, these systems may be perfect for the person who doesn’t need much finished product but would like to make their own medicine using a simple low-cost system. The other advantages to fluorescent systems are: they don’t use much electricity; they don’t produce much heat; they are easy to find and easy to work with; and they are relatively inexpensive and safe. Suffice it to say that any successful indoor grow system will require at least a few fluorescent lights, and some of the simplest of the successful indoor grow systems may be totally fluorescent.

HID Lights

The metal halide (MH) and high pressure sodium (HPS) are the main light sources for the indoor grow industry. These systems were developed more than twenty years ago and have undergone many improvements and advances since. They are capable of producing and delivering high-intensity, full-spectrum light. They are modified streetlights, designed to grow plant material. The intensity of the light is far more potent at greater distances from the bulb than any other systems available. The MH and HPS systems come in varying wattage sizes, styles and even different light bandwidth specifications.

The most common wattage sizes are 400 and 1000 watts, although 75, 150, 250, 360, 430, 600 and 1500 wattages are also available and useable. There are also choices of horizontally or vertically mounted bulbs, and type of reflectors. These specifics are best considered after visiting your local grow store and seeing what products are available. From there, one can decide what will best suit one’s unique needs. My personal preference is for a combination of 430-watt, horizontally mounted HPS systems coupled with 400-watt, vertically mounted MH systems in small spaced flower cycles. This combination seems to utilize the best of both worlds. For larger spaces, the 1000-watt systems are virtually unbeatable.

There is a difference between MH and HPS systems in the type of light they produce. Both are relatively full-spectrum devices, however MH systems emit more in the ultraviolet range while HPS systems tend to emit more in the infrared range. Due to the fact that the late summer evening sun (the light most prevalent to budding plants outdoors) tends to emit more in the infrared range, HPS systems have been valued more for their bud cycle capabilities, whereas MH systems have been favored in the vegetative stage. I have found this to be true in regard to production. However, I have also observed that the MH systems tend to produce more colorful finished products (blues, reds and purples) when used either alone or in conjunction with HPS systems in the flower cycle. Again, experimentation will yield personal favorite results.

The difference between horizontally and vertically mounted bulbs has to do with how they disperse light. The greatest amount of light comes from the middle of the bulb, out its side. Therefore, horizontally mounted bulbs tend to direct the light down while vertically mounted bulbs tend to direct the light out to the sides. As for overall intensity of light, horizontally mounted bulbs are superior.

MH and HPS systems have two main parts: The ballast and the bulb with socket. The ballast is a large metal box that houses the transformer, capacitors, starters and other “guts” of the system. The ballast also has at least two cords attached. One cord is the electric plug, wired for either 110-volt or 220-volt usage (other wire connections are possible, but 110 and 220 are the most common in North America). The other wire leads to the socket and bulb setup that may or may not be attached to a reflector. (Generally, reflectors are always used with horizontally mounted systems and considered optional with vertically mounted bulbs.) The length of these cords is sometimes optional, prompting more planning and consideration.

The benefits and advantages of the MH and HPS systems are obvious to anyone who sees them in action. These devices radiate an intensely bright light. The disadvantages to these systems are their consumption of electricity and the amount of heat they make as a by-product. Again, careful planning maximizes the efficiency and safety of these systems. Due to their high demand for electricity, fire hazards need extra consideration when using MH or HPS systems. The electric wire supplying the MH and HPS systems should be inspected and, if need be, replaced prior to production. The wiring needs to be of adequate quality before you begin using any high amperage equipment. To avoid creating a fire hazard, make certain that the electric system supplying the grow room(s) be in perfect running order. When in doubt, have an expert check it out, preferably before you begin. There is no real solution for the consumption of electricity. It is merely considered part of the cost of production and should be accepted as such. Don’t be stupid, and try to steal power. It is a very bad idea.

There are several ways to effectively deal with the heat. The most common way of dealing with heat is adequate ventilation (see chapter 5: Air Circulation and Temperature). But there are a few other tips I would like to offer now. The first is to keep the ballast in a separate room, away from the bulb. Both the bulb and the ballast produce heat. If the cord between the ballast and the bulb is long enough, it is very simple to keep the two separated. This way, the ballast and bulb are producing heat in two locations and not in the same room as the plants.

Another tip for keeping the heat down is also a very simple one: whenever possible, run your lights at night. In most parts of the world, at most times of the year, nighttime baseline temperatures are generally cooler than daytime temperatures. This difference is usually twenty to forty degrees (except for tropical and equatorial zones). The average light cycle in the bud stage is twelve hours on and twelve off. Therefore, the most opportune time to run the lights would be between 8 PM and 8 AM —the coolest times of day.

There exist a few devices created to help lower the temperature associated with MH and HPS systems. One of these is the vented hood. This device is designed into the reflector, and can be modified to accept either a vent fan or conduit leading to a fan. It allows cool air to be drawn in to the grow room and hot air around the bulb to be vented outside of the grow room. Though these systems can be slightly expensive, they are very efficient and work well.

There is also a device that utilizes water to cool off the heat from the bulb. This system circulates water via a pump through a fan-cooled radiator and a series of tubing that runs up and around the bulb. Though this device is somewhat complicated and expensive, it works very efficiently as well.

Special caution needs to be taken when watering the plants or any time liquid has a chance of coming in contact with a hot bulb. If it gets wet while hot, the bulb may explode violently. Exercise the necessary precautions when handling liquid around the bulb.

Reflective Material

Using reflective material on the walls, ceiling and even the floors of the grow room increases the efficiency of light usage. The three most common types of reflective material are white plastic, Mylar, and flat white paint. The advantages of white plastic are that it is relatively inexpensive and easy to use. The disadvantages are that it is not as efficient at reflecting light as Mylar or flat white paint. The advantages to Mylar are that it is super reflective, relatively easy to use and it also blocks many of the rays detectable by infrared scanners and scopes (where that type of security is an issue, that is). The disadvantage is its cost. The advantages to flat white paint are that it is cheap and easy to use and also the best overall reflector of the three. The disadvantage is its permanence. These products help maximize the efficiency of any light source by directing otherwise unused light back to the plants.

Using Sunlight

I cannot let this piece end without putting in a word for good old sunlight. Let me state for the record that in my humble opinion there is no complete substitute for our beloved Sol when it comes to producing light, especially when it comes to plants. And the Sun is out there for anyone to use free of charge each and every day. There exist windows, skylights and now even “solar tubes” that are used for bringing sunlight indoors. This light would work perfectly for general plant production. The solar tube is an amazing device that is capable of collecting the sunlight and delivering it in full glory to the indoor environment. A solar tube could be built into a small private area such as a closet or pantry. The tube can also be opened or closed so that flowering manipulation could be easily maintained. It is also possible to control light cycles with windows and skylights by using a common shade and, unless some form of automatically timed device is used, a bit of daily discipline.

If a person lives on a relatively private piece of land, or has an area unseen by prying eyes, putting plants outside in buckets and bringing them in every day is another option to utilizing the Sun. This method has worked well for many people. Moving the plants in and out everyday by hand is done to force early flowering, especially in southern areas. This allows a person to grow outdoors yet harvest well before the traditional harvest time. It is a discipline. This method also allows more harvests per year than if strictly grown outdoors.

A person with a barn or garage, or even a shed, could install a translucent piece of material in a south-facing roof (north-facing in the southern hemisphere). This would allow enough light in for adequate plant growth while also keeping the garden “secure.” In the garage or barn, a loft could be constructed beneath the translucent piece (or pieces). Be creative and innovative! And always keep sunlight in mind when considering a light source for plant production.