Whether you’ve invested $20 in your lighting setup or $200, chances are good that you want to get the absolute most use out of your lights as possible. This means you don’t want to waste any of those precious lumens on the walls or floor of your grow. To limit the amount of light that goes to waste there are several things you can do.
First, you can invest in a good reflector. A reflector or a reflective-hood attaches to your light in order to reflect and direct the light downwards. After all, your plants are beneath the light bulb, not above it, so you don’t need to light the ceiling. One of the best reflectors available, especially for a smaller grow such as a 4’ x 4’ closet or stealth grow, is the Xtrasun Wing.
In addition to a hood or reflector, you can also increase the amount of light that is reflected back onto your plants (where you actually want it to be) by painting the walls of your grow room white. Choose a nice flat or matte white paint as opposed to a glossy white paint; at first thought, you might be inclined to choose glossy white paint for better reflectivity, but the gloss can actually cause hot spots to form, leading to the potential for burning your plants.
Some growers, especially those on a tight budget, choose to use tinfoil to line the walls of their grow room as opposed to a white paint. Unfortunately, tinfoil is much more likely to lead to hot spots, and its reflectivity isn’t as good as white paint, either. If you must use tinfoil, though, use the duller, backside of the tinfoil vs. the shinier front; this will reduce the likelihood of hot spots.
As an alternative to paint or tinfoil, some growers also opt for Mylar film. Mylar is highly reflective and can be used to cover the walls of your grow room, ensuring that as much light as possible in reflected away from the walls and back to your plants. A more durable version of Mylar, called Foylon, is also very popular among cannabis cultivators.
And for the ultra-careful or the mildly-paranoid grower, C3 anti-detection film is a specialized version of Mylar that, in addition to bringing you the awesome reflectivity of Mylar (capable of reflecting 92 – 98% of all light) also blocks up to 90% of the infrared radiation (i.e. your grow room’s heat signature) from escaping your grow room. This is perfect for ultra-stealthy grows.
One good way to get an idea for how well your reflector and/or walls are reflecting the light is to purchase a basic light meter. Light meters are available online and in many garden supply stores, and range in price from simple and inexpensive to the ultra-professional wallet busters.